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MAPPING THE FIELD • BOMB-GRADE • 20TH-CENTURY COPERNICUS SECRET LIFE OFMIND NEUTRONS • COMPUTERSILVER KIRIGAMI • SCIENCE MINUS SCHOOL
AMERICAN
Scientist January–February 2011
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Chromosomes Revealed—At Last!
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AMERICAN
Scientist Departments
Volume 99 • Number 1 • January–February 2011
Feature Articles
2 From the Editor
48 Chromatin Evolving Much about the function and evolution of the chromosome remains a mystery Gregory A. Babbitt
3 Letters to the Editors 6 Macroscope Spectator at the disaster John Dvorak 10 Computing Science Flights of fancy Brian Hayes 16 Engineering Bridges of the Mediterranean Henry Petroski 20 Marginalia The biology of what is not there Robert L. Dorit 24 Ethics A troubled tradition David B. Resnik
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32 Fractures and Bindings of Consciousness Seizures suggest how consciousness is bound in large-scale cerebral networks Don M. Tucker and Mark D. Holmes
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28 Science Observer Cracking cellular motion rGet a grainy griprUnauthorized reproduction is not prohibitedr In the news
56 American Scientist Classics: Galaxies An astronomer and a science historian revisits Harlow Shapley’s 1942 article Virginia Trimble
68 Sightings Mapping macromolecules in cells
Scientists’ Bookshelf 70 Book Reviews Childhood r Hunter-gatherers r Cyberneticians rHotter cities
From Sigma Xi 90 Distinguished Lectureships, 2011–2012 93 Sigma Xi Today Sullivan selected president-elect r 125th anniversary
The Cover
American Scientist
40 40 From Treasury Vault to the Manhattan Project It took 14,000 tons of government silver to build the world’s first atomic bonb Cameron Reed
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DNA is an exotic polymer that measures on the atomic scale in one dimension (width) and the human scale in the other (length). Every human cell contains about two meters of DNA, almost all wound around proteins called histones to form nucleosomes. Nucleosomes group together to form higher levels of structure about which, after a hundred years of investigation, we still know very little. We do know that the DNA packs tightly in some chromosomal territories and loosely in others, forming sheer walls and intergenic fissures, as seen in the cover image from a 3D animation by renowned molecular animator Drew Berry. (The image at left includes structural proteins of the nuclear envelope not shown on the cover.) In “Chromatin Evolving” (pages 48–55), evolutionary biologist Gregory Babbitt reviews what we know and don’t know about the higher-level structures formed by DNA, including how they are investigated, how they affect gene regulation and how they evolve.
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From the Editor
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AMERICAN
Anniversaries
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e’re now little more than a year out from American Scientist celebrating its 100th anniversary, and in anticipation, we continue the tradition of republishing landmark articles (“Classics”) accompanied by modern commentary. A year ago the Classic was Gilbert N. Plass’s 1956 article “Carbon Dioxide and the Climate,” and in this issue we bring you Harlow Shapley’s 1942 piece “Galaxies” (pages 56–65), with a review by University of California, Irvine astronomer and science historian Virginia Trimble. Shapley’s name may be a bit more familiar to readers outside the field of astronomy than Plass’s was to nonclimate scientists, but there’s really a good deal more to the story than that. The January 1942 issue was the first to carry the name American Scientist, as you can see in the accompanying photograph. But there’s even more to the story than that. Those of you who are savvy to printing processes can probably tell that “American Scientist” was an afterthought, added after the cover had already been printed. The density of the ink is the giveaway. There is a suggestion in the Society news section of the issue that different titles be sought for the publication, but it wasn’t until the next issue in April 1942 that the Sigma Xi Executive Committee announced its unanimous decision to change the name to American Scientist—The Sigma Xi Quarterly. Was it happenstance that Shapley served on the Executive Committee or that his article appeared on page 1 of the inaugural American Scientist? In any case, I hope you’ll enjoy Shapley’s eloquent stargazer perspective as much as I did, and I think you’ll find that Virginia Trimble does a masterful job of placing Shapley in the context of his time. As she notes, having one’s scientific work scrutinized nearly 70 years after the fact is not a prospect most investigators would relish.
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here’s also another new piece of editorial matter in this issue that reflects yet another anniversary: Sigma Xi’s 125th. Over those years ethics in research has been one of the, if not the, top priorities of the Society. In keeping with that, 2011 is Sigma Xi’s Year of Ethics, and accordingly, we will have periodic columns during the year focusing on peer review and authorship. The first of those, “A Troubled Tradition” (pages 24–27), is by National Institute of Environmental Health Sciences bioethicist David B. Resnik, who has published one of the few studies on the prevalence of the types of ethical issues that may arise in the conduct of peer review and publishing. Even if you’re not actively involved in doing and publishing research, I think you’ll find that this essay will help you understand the results of science better and give you a deeper appreciation of the process.
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inally, we all bid a warm welcome to returning “Computing Science” columnist Brian Hayes. The past year has seen a fine selection of standins while Brian pursued other projects, but to put it simply, there is only one Brian Hayes. Lucky for us, “Flights of Fancy” (pages 10–14) shows that he’s clearly spent some of the past year looking skyward.—David Schoonmaker
Scientist www.americanscientist.org
VOLUME 99, NUMBER 1 Editor David Schoonmaker Managing Editor Morgan Ryan Senior Editor Fenella Saunders Associate Editor Catherine Clabby Editorial Associate Mia Smith Art Director Barbara J. Aulicino Assistant Art Director Tom Dunne Senior Writer Brian Hayes Contributing Editor Christopher Brodie Contributing Editor Elsa Youngsteadt SCIENTISTS’ BOOKSHELF Editor Flora Taylor Assistant Editor Anna Lena Phillips AMERICAN SCIENTIST ONLINE Managing Editor Greg Ross Publisher Jerome F. Baker Associate Publisher Katie Lord Marketing Associate Eric Tolliver ADVERTISING SALES Advertising Manager Kate Miller BEWFSUJTJOH!BNTDJPSHt ___________ EDITORIAL AND SUBSCRIPTION CORRESPONDENCE American Scientist P.O. Box 13975 3FTFBSDI5SJBOHMF1BSL /$ tGBY FEJUPST!BNTDJPOMJOFPSHtTVCT!BNTDJPSH ____________ ________ PUBLISHED BY SIGMA XI THE SCIENTIFIC RESEARCH SOCIETY President Joseph A. Whittaker Treasurer #SBEGPSE#8BMUFST President-Elect Michael Crosby Immediate Past President James F. Baur Executive Director Jerome F. Baker PUBLICATIONS COMMITTEE Chair A. F. Spilhaus, Jr. Jerome F. Baker, Paul C. Kettler, David Schoonmaker American ScientistHSBUFGVMMZBDLOPXMFEHFT TVQQPSUGPSi&OHJOFFSJOHwUISPVHIUIF-FSPZ Record Fund. Sigma Xi, The Scientific Research SocietyXBT GPVOEFEJOBTBOIPOPSTPDJFUZGPSTDJFOUJTUT BOEFOHJOFFST5IFHPBMTPGUIF4PDJFUZBSFUP GPTUFSJOUFSBDUJPOBNPOHTDJFODF UFDIOPMPHZBOE society; to encourage appreciation and support PGPSJHJOBMXPSLJOTDJFODFBOEUFDIOPMPHZ BOE to honor scientific research accomplishments. Printed in USA
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Letters to the Editors Engineering Real Energy Solutions
To the Editors: I agree in principle with Alan Pavlak’s argument in his Macroscope “Strategy Versus Evolution” (November–December) that a systemwide approach to carbon emission reduction is appropriate. But I believe Dr. Pavlak makes critical errors on important points. First is the remarkable omission of the most obvious opportunity to reduce emissions: conservation. Granted, this is a policy-based solution and not what Dr. Pavlak chooses to dabble in. But opportunities there make the engineering solutions much easier, maybe even attainable. Likewise, he ignores the possibility that we could achieve further efficiency in electricity use and in transportation, again gaining ground on the goal of 83 percent reduction in CO2 by 2050 without reinventing our entire energy complex. And his conclusion that nuclear energy will be the backbone (if not the entirety) of our electricity and transportation systems is troubling. Once again we would place ourselves in the full embrace of a technology that is based on a nonrenewable resource largely obtained from outside our borders. If Dr. Pavlak were assigned this project, I believe his strategic plan would have to contain lots of the silver buck-
shot he casually dismisses. That includes conservation, efficiency, wind (surely less of a challenge to integrate into the grid than he opines), solar and other truly renewable sources. Mark McClain Salem, VA Dr. Pavlak responds: The main point I was trying to make is that we must start thinking strategically about clean energy systems or we will make big mistakes, charge down dead ends and invest in systems that will have to be discarded. We need simple architectural models of end-state system configurations to clarify which concepts can achieve sizable emission reductions. Wind power is a great example. People point to grid-scale storage, long-distance transmission and the smart grid as ways to increase wind penetration. It all helps a little bit. But as soon as we put numbers to it, when we conceptualize a zerocarbon grid based on what we know today, wind does not work. Mark McClain is quite correct to point to conservation and efficiency as high-return opportunities. Indeed we should have a metric such as a dollar-per-ton CO2 emissions decrease to identify low-hanging fruit and to prioritize investments. But how much can we realistically expect to
achieve with this? Based on actual emissions reductions to date (mainly from a onetime shift to natural gas), my hope is that conservation and improved efficiency can cap emission growth, even as the world’s GDP continues to grow. But an 83 percent overall reduction in CO2 emissions is huge! It will require both an electric power grid and motor vehicle fuel that is zero-carbon (or not fossil fuel). This will require rethinking our entire energy complex. Poetry and Science Still Talk
To the Editors: I’d like to comment on two items in the Science Observer article “Epic Science” (September–October). First is the statement that by 1900 “the long poem designed to inspire interest in science … was gone.” True, long poems are rare, but occasionally they are produced. A fine example is “The Dance of the Solids” by John Updike. It is not book length, like those discussed, but it cleverly describes the multidisciplinary field of materials science and engineering. Second, in paraphrasing Hugues Marchal, the article suggests that there are “several reasons for the fall of the longer scientific poem,” one of which is “the increasing speed of scientific discovery (which contrasts with the
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American Scientist (ISSN 0003-0996) is published bimonthly by Sigma Xi, The Scientific Research Society, P.O. Box 13975, Research Triangle Park, NC 27709 (919-549-0097). Newsstand single copy $4.95. Back issues $6.95 per copy for 1st class mailing. U.S. subscriptions: one year $28, two years $50, three years $70. Canadian subscriptions: one year $36; other foreign subscriptions: one year $43. U.S. institutional rate: $70; Canadian $78; other foreign $85. Copyright © 2011 by Sigma Xi, The Scientific Research Society, Inc. All rights reserved. No part of this publication may be reproduced by any mechanical, photographic or electronic process, nor may it be stored in a retrieval system, transmitted or otherwise copied, with the exception of one-time noncommercial, personal use, without written permission of the publisher. Second-class postage paid at Durham, NC, and additional mailing office. Postmaster: Send change of address form 3579 to Sigma Xi, P.O. Box 13975, Research Triangle Park, NC 27709. Canadian publications mail agreement no. 40040263. Return undeliverable Canadian addresses to P. O. Box 503, RPO West Beaver Creek, Richmond Hill, Ontario L4B 4R6.
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time required to make good poetry).” One could argue that the time required to do good science is often appreciable and may easily exceed the time needed for a talented individual to produce a good poem. The apparent speed of scientific discovery results from open communication involving thousands of investigators, whereas most poems are produced by individuals. Both require effort and both are valuable. David A. Rigney The Ohio State University
online @ AMERICAN
Scientist.org Find feature articles, columns, book reviews and Science Observer reports from our latest issue at http://amsci.org. Also, see previous issues dating back to 1998. (Access to some material is limited to Sigma Xi members and subscribers.)
Exclusively online 2010 coffee-table books A slide show featuring images from some of our favorite largeformat books of the past year http://amsci.org/coffee-table-2010 Biological anthropologist Melvin Konner’s book picks In a Scientists’ Nightstand, Konner discusses his favorite books and what he’s reading now. http://amsci.org/konner Science in the News A concise roundup of science stories collected each weekday from multiple media outlets, with links to the original articles http://amsci.org/sitn E-Newsletters Science in the News Daily, Scientists’ Bookshelf Monthly and more http://amsci.org/enews American Scientist on Twitter twitter.com/AmSciMag
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Getting Science Education Right
To the Editors: I was glad to read “The 95 Percent Solution” (November–December). I offer kudos to John H. Falk and Lynn D. Dierking for an insightful, accurate and long overdue piece on the importance of free-choice science learning. I roundly support their findings and recommendations and proffer that a good part of mainstream academia’s reluctance to accept them could be based on good old-fashioned empire protectionism, or maintenance of the status quo. I feel their findings could be applied equally to Canadians. And there needs to be more discussion about the lack of vehicles or tools for validating and legitimizing learning outside of a formal academic setting. There is far too much emphasis in our society on formal credentials and acquisition of academic lettering, rather than focusing on acquired knowledge and abilities—regardless of how and where obtained. As the authors note, research by Mami Berendsen of the NASA Night Sky Network found that some “amateur” astronomers possess more knowledge than university undergraduates do. But in the absence of lettering such as B.Sc. (a bachelor of science degree) to validate and support their understanding, people engaged in science in formalized settings can be stymied in advancing further. This needs to change. Winston Stairs Oshawa, Ontario To the Editors: We were disappointed by the interpretation of data and the recommendations in “The 95 Percent Solution.” We respect the excellent National Academies of Sciences 2009 report “Learning Science in Informal Environments: People, Places, and Pursuits,” by Philip Bell, et al. It explains the importance of informal science education. But the excellence and importance of formal science education are totally lost in Falk and Dierking’s presentation. It is as though the authors suggest we roll over and give up because some science instruction in some schools has received bad test scores. If the athletics and physical education professionals received a similar set of recommendations—just have stu-
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dents go to ball games, watch television or take a field trip and let others have all the fun (and spare us the time and expense of their direct participation)— they’d deem it totally inappropriate. The same should be true for science education. A laissez-faire approach hasn’t worked well with science education. Noted science educator Mary Budd Rowe once asked a relevant question that went, roughly, like this: Are you a crapshooter or a bowler? Crapshooters believe they have no control over their future and can’t improve their odds. But bowlers know they can improve their game with practice. When it comes to education, we’re with the bowlers. We believe that Falk and Dierking should revisit the data and reformulate recommendations that would help the in-school science education community improve its game. M. Patricia Morse University of Washington David Kennedy Olympia, WA Drs. Falk and Dierking respond: We are delighted that our article generated considerable discussion and we appreciate all of the comments, positive and negative. We want to clarify two points. First, we never claimed that freechoice or informal learning accounts for 95 percent of all science learning or that schooling contributes little to the public’s understanding of science. We did argue that lifelong, out-of-school experiences contribute far more to that understanding than traditionally has been acknowledged. Second, current data do not allow direct comparisons of the efficacy of learning in and out of school, but it is clear that both make important contributions. The data do suggest that outof-school experiences might be particularly important for underserved youth and for adults. Ultimately this need not be an either-or proposition. Learning is cumulative and distributed. No one learns anything in only one place or at one time. We suggest that policymakers require schools, free-choice learning settings and higher education institutions to collaborate as equal partners and create lifelong science, technology, engineering and mathematics (STEM) education. That would be a useful alternative to educational policies that focus solely on in-school science education. Such an approach would leverage what
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we know about the interconnectedness of learning across a lifespan. It would also, of course, have serious implications for how we invest our finite educational dollars. Teach Us Teachers
To the Editors: I read Roald Hoffmann and Saundra McGuire’s Marginalia article “Learning and Teaching Strategies” (September– October) with great interest. But when I read that Professor McGuire had “seen countless students improve their test scores from below 50 to over 90 in a matter of weeks, just by using metacognitive learning strategies” I thought: How can you hold out on us like this? Any approach with such results deserves to be described in detail! Can she suggest places to learn more about these metacognitive strategies—either materials to read, or even better, workshops or people to interact with? I need useful things to say to the struggling students in my first-year biology class. Max Taub Southwestern University
Dr. McGuire responds:
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MCCCTR/metacognition.htm#VI) or visit the Oncourse Workshop (http:// _____ www.oncourseworkshop.com/) and _______________________ the Center for Academic Success (www. ____ cas.lsu.edu). ________ ________________________
In 2001, after 31 years of teaching chemistry without teaching metacognition, I too was amazed to realize that improving student learning could be as straightforward as teaching students how to analyze their own thinking and implement new strategies. Consider the physics student whose score rose from 54 to 91 after she realized she had been laboring on the lowest level of Bloom’s taxonomy (memorization) but could work at the higher levels (application and analysis). She also changed her approach to homework by working the problems without using examples as a guide. Here are two metacognitive strategies that we at LSU have found to be most helpful: 1) Instruct students to study their material as if they must teach it; 2) Teach students to focus on the higher levels of Bloom’s taxonomy. After their scores improve, their increased self-confidence leads them to use these strategies more. This, in turn, leads to more improvement and they get hooked. For more information, read William Peirce’s “Metacognition: Study Strategies, Monitoring, and Motivation” (http://academic.pgcc.edu/~wpeirce/
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How to Write to American Scientist
Brief letters commenting on articles that have appeared in the magazine are welcomed. The editors reserve the right to edit submissions. Please include a fax number or e-mail address if possible. Address: Letters to the Editors, American Scientist, P.O. Box 13975, Research Triangle Park, NC 27709 or
[email protected]. _________________ Erratum Due to an editing error in “Gifts and Perils of Landslides” (September–October), the Figure 11 caption misstated the likely date for the origin of carvings along a onetime pilgrimage route through the Karakoram mountains. Some rock carvings along the upper Indus streams may go back 5,000 years. But the Buddhist renderings at SatparaSkardu likely date from no earlier than the 7th century.
An integral piece of the bigger picture.
Marginalia Barbara Aulicino and Robert L. Dorit Page 26
Ethics Barbara Aulicino
Fractures and Bindings of Consciousness Figures 2, 3, 7 Stephanie Freese Figure 8 Tom Dunne From Treasury Vault to the Manhattan Project Figure 5 Tom Dunne Figure 7 Barbara Aulicino Chromatin Evolving Figures 3, 5 (right) Emma Skurnick Figure 4 Morgan Ryan
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Macroscope
Spectator at the Disaster John Dvorak
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remember the moment when I heard the first report. The date was February 26, 2010. I was at home listening to the tease for the late-night news on television. The news anchor, in a clear and slightly exaggerated tone, announced that a major earthquake had struck Chile. A single thought formed instantly in my head—tsunami! To those of us who live on islands in the middle of the Pacific, the thought is never far off that a distant earthquake might generate a sea wave that races across the ocean, runs up on shore and sweeps away a community. In Hilo, Hawaii, where I live, tales are told of such a wave in 1946, generated by an earthquake in Alaska. The onslaught began as a pull-back of the sea. Within minutes, those who had gathered along the edge of the strangely emptied Hilo Bay witnessed the sea return as a wall of water. The great wave slammed into a row of buildings that outlined the edge of the bay, then plowed those buildings into the buildings on the other side of the street. Ninety-six people drowned. The area swept vacant by the wave is now a city park where kids play soccer. The next earthquake-generated wave to hit Hilo was in 1960. A friend who was then a teenager told me that as soon as he and his pals heard that a wave was rushing toward the island, they hustled down to the edge of Hilo Bay to watch it come in. They stood on a small iron bridge close to the shoreline positioned no more than a few feet above high tide. The first wave arrived on schedule and passed under the bridge. Twenty minutes later, a second wave arrived and did the same. Disappointed, my friends and his pals John Dvorak began his scientific career studying volcanoes. Today he operates a telescope at Mauna Kea for the Institute for Astronomy, University of Hawai’i. Mail: Institute for Astronomy, 640 S. Aohoku Street, Hilo, HI 96720. E-mail: ____________
[email protected] 6
Nature in violent action can be spectacle, tragedy and object of scientific wonder all at once left and went home. Later, a third wave arrived. This one crested fourteen feet over the bridge. Seawater surged as far as a mile inland. Sixty-one people died. Hundreds of homes and businesses were destroyed. The 1960 wave was generated by an earthquake in Chile. On the night that I heard the report of the latest Chilean quake, local news crews assembled outside the building that houses the Pacific Tsunami Warning Center, located in Honolulu. A spokesman stood outside before a cluster of microphones and informed the public that a large earthquake had just occurred in Chile, similar to the one in 1960, and that a Pacific-wide tsunami was possible. Nothing more would be known, he said, for at least a few hours. By then, the anticipated wave would have passed a buoy tethered in the ocean and designed specifically to detect such waves. With nothing more to learn, I went to bed. I awoke at five o’clock the next morning and turned on the television. There it was—the scene I had imagined for years. The same spokesman stood in front of the warning center, reading an official statement. A wave had been generated and was spreading across the Pacific. He then read a list of the times
the first wave was expected to arrive at specific places around the islands. The first wave would arrive in Hilo Bay at 11:19 a.m. I woke my family and we made plans to watch the event. By nine o’clock we were standing on a hillside about a mile from the shoreline at a place that offered an excellent view of the bay. The weather was clear and sunny. It was Saturday, so there were no concerns about children in school. We were standing in a crowd of other families. Among those in the crowd were many who lived near the coastline in areas that might be swamped by the approaching wave. As far as I could tell, no one had stuffed their cars or trucks with packing boxes and mattresses to move their worldly possessions to high ground. All they had transported were their vehicles and their pets. The mood of the crowd was neither festive nor somber. Everyone was simply waiting. At ten o’clock the first sirens sounded. Thirty minutes later, I heard over a car radio that all coastal roads were closed. Police stood at barricades partway down the hillside to prevent anyone from entering the closed area. At eleven o’clock the sirens sounded a second time. That signaled that the first wave would arrive in 20 minutes. Exactly at the predicted time, the entrance to Hilo Bay began to turn brown. Someone shouted, “It’s starting!” The brown patch grew as seawater was pulled out of the bay, the force of the water kicking up silt from the bottom. A reef of black rocks, normally visible only during extreme low tide, appeared just off a popular picnic spot known as Coconut Island. It was the clearest sign that the water level in the bay was dropping. After 10 minutes, the rocks were covered again by seawater. A few more cycles, each lasting 20 to 30 minutes, the water level changing no more than a few feet, and the event was over. The city of Hilo had been spared.
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Ancient and modern, awesome and terrible merge in this woodblock print of the Great Kanto Earthquake of 1923 by Shiun Kondo. (Image courtesy of artelino, www.artelino.com.)
Through it all, even as I was preparing to go to bed the previous night and, later, as I stood with my family and my neighbors and watched the water recede and recover, I kept thinking about those other people, thousands of miles away, somewhere along the coast of Chile. An unknown number of souls were trapped beneath the rubble of buildings that had collapsed during the earthquake. At that moment they were wondering whether they would ever be rescued. Close Encounters
Grove Karl Gilbert, one of the first geologists to survey the American West and later acting director of the United States Geological Survey, once wrote, It is the natural and legitimate ambition of a properly constituted geologist to see a glacier, witness an eruption, and feel an earthquake. The glacier is always ready, awaiting his visit; the eruption has a course to run, and alacrity only is needed to catch its more important phases; but the earthquake, unheralded and brief, may elude him through his entire lifetime. www.americanscientist.org
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Gilbert’s encounters with glaciers and volcanoes came easy. In 1899, while on a scientific expedition to Alaska, he spent months mapping, measuring and photographing nearly 40 glaciers. He had his encounter with active volcanoes when the expedition’s small ship came within sight of Pavlov volcano, which Gilbert later reported was steaming from a spot high on the peak, and then sailed close to Bogoslof Island, a mound of steaming crags that had risen recently from the sea. But the shaking of an earthquake kept eluding him. He left Alaska a month too soon to feel the ground rock back and forth during a magnitude 7.4 earthquake near Yakutat Bay, which raised a 40-foot wave that washed the shoreline on which Gilbert had recently stood. Gilbert seemed genuinely disappointed to have missed it. Nearly 30 years earlier, he had been “tantalized,” so he wrote, when he left central California after an extended stay of several months and returned east just weeks before the Great Inyo Earthquake of 1872 shook the western half of the continent, from Oregon to Central America. His appointment with geological upheaval finally came on April
18, 1906. That morning, he was asleep at the Faculty Club at Berkeley—in town to attend a meeting about California mining and how it was ruining the environment—when, “by a tumult of motions and noises,” he was awakened and became aware “with unalloyed pleasure” that “a vigorous earthquake was in progress.” The destruction in Berkeley was “trivial” by his estimation, but within two hours of the earthquake, he learned “that a great disaster had been wrought on the opposite side of the bay and that San Francisco was in flames.” It took him two days to find passage there by ferry. When he arrived, the city was still burning. He chronicled the progress of the fire, watching as block after block of close-set wooden houses were consumed by flames. At one point, he recorded in his notebook the time it took for a two-story building to be destroyed: “roof gone in seven minutes; first falling of wall in nine minutes; flaming ruins in twelve minutes.” After the fire ended, he set off, again by ferry, to the area hardest hit by the earthquake, which was on the north 2011 January–February
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side of the bay, and there he began a formal scientific investigation. Gilbert would author a famous government report about the earthquake. At the end of the report, he considered the possibility that future earthquakes might strike San Francisco. Should a repeat of the 1906 event be expected within the lifetimes of the next few generations, he wondered, or had the recent calamity given the area long-term immunity from another violent disturbance? He had no answer. But he was sure that “timidity will cause some to remove from the shaken district and will deter others who were contemplating immigration.”
multistoried buildings in Concepión, the second largest city in the country. And during the spring months, I followed, as many did, the progress of repeated ash clouds erupted from an Icelandic volcano, the clouds wreaking havoc on international air travel and crippling world commerce. And so I share the humanist view and feeling of my seismological friend. But, like Grove Karl Gilbert, I am drawn to experiencing great geologic forces, wanting to be present when they are unleashed. It should come as no surprise that, like Gilbert, I hope to experience the shaking of a major earthquake. I am quite sure others harbor a similar, secret wish.
Hazard as an Occupation
Recently, I asked someone who was retiring after 30 years of studying earthquakes, which included a substantial tenure as head of the USGS Earthquake Hazards Program, whether he was disappointed that a major earthquake—on par with the 1906 event—had not happened on his watch. He answered no. There was too much suffering after such events, he said. He had dealt with the aftermath of several significant quakes, including the 1989 Loma Prieta earthquake that, among other things, caused a span of the Bay Bridge that links San Francisco and Oakland to collapse. The official death toll from the earthquake was 57. Property loss was valued at $6 billion. As a result of the disaster, a new Bay Bridge is under construction. Planners hope it will be completed before the next big earthquake shakes the Bay area. Understand that I am not wishing for destruction by natural forces, but I know that such events are inevitable. Also, I am no stranger to such catastrophes. I studied erupting volcanoes for 16 years. I have seen bodies cremated by passage of the hot hurricane-force wind known as nuée ardente. And I have stood on the hard surface of a recently congealed mudflow, knowing that thousands of people were entombed beneath my feet. In January 2010, I watched, as millions of others did, with near disbelief as television cameras showed the destruction wrought in Haiti after an earthquake killed nearly a quarter million people and left the capital city, Port-au-Prince, in ruins. A month later, the earthquake in Chile, which was a thousand times stronger than the 1989 Loma Prieta earthquake, collapsed 8
Disaster Psychology
Years ago, during an informal discussion about earthquakes and how they should be studied, I commented to colleagues that instead of adding yet another seismologist or geologist or geodesist to the group, adding a psychologist would make more sense. One of the major goals of the Earthquake Hazards Program is to keep the public informed about the perils associated with such events. It seemed to me imperative that we, as scientists, understand how the public will react to the sort of information we might be called upon to provide—potentially terrifying information about imminent cataclysms. My suggestion was met with blank stares. I have also suggested that once the prediction of earthquakes becomes commonplace—and I think it is inevitable that, someday, earthquake prediction will be on par with forecasting the path and strength of hurricanes, if not rising to the certainty of predicting the tides—that contingency plans will have to be made for the crowds that will assemble in the forecasted epicentral area to feel the ground shake. Bear with me on this. I had an experience years ago that is pertinent to this question. It happened on the Nevada desert back in the days when underground nuclear tests were still conducted. Whenever such a test was scheduled, an army of graduate students was sent out across the desert to station ourselves at regular intervals along a line that ran radially away from the blast. (The point of the exercise was to study the structure of the Earth’s crust.) Each of us was equipped with a portable
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seismograph to record the precise time the initial ground shaking arrived from the blast. For one test, I was lucky and drew the lot that put me second closest to the detonation. I arrived at my assigned position early in the morning. I knew the exact second when the ground would start to vibrate. And I knew the direction the wave would come from. With five minutes to go, I made sure I was standing on firm ground and facing in that direction. A minute before the wave was scheduled to arrive, I remember feeling a surge of adrenaline rush through my body. Then, with a moment to go, I saw the ground rippling on the distant horizon. In less than a breath, the wave had passed under me. I could distinctly feel the pulses running up my legs and through my body. The whole experience lasted barely a second. I turned after the wave passed me and watched it disappear over the other horizon. In the vernacular of my generation, it was better than an E ticket at Disneyland. From that experience, I feel justified in predicting that there will be professional and amateur earthquake chasers. Droves of people will flock to any area that is predicted to have a major earthquake, arriving by whatever means required to be there at the appointed time. It will be much as it is today when crowds of people gather along the strip of land that the moon’s shadow follows during a total solar eclipse. Travel agencies will book tours to “Ride the Earth’s Crust.” Hawkers will sell T-shirts and commemorative plates. From a different perspective, people who already live in seismic zones will be better prepared than any group before them for the strong shaking that is about to come. Such a world is in the future. How far ahead, I do not know. In the meantime, I struggle with the dilemma of the “properly constituted geologist.” I desperately want more experience of the great forces of nature. I want to hear the acoustically epic roar of the rupturing crust, of the ocean emptying from its basin and then returning. Yet I cannot sincerely wish for it, because I know, as perhaps only geologists and the victims of natural cataclysms do, how much human suffering is mixed in with the flows and ejections of nature in its most violent moments.
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Flights of Fancy Brian Hayes
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thousand starlings rose in unison from trees along a riverbank. The ascending cloud of birds took the form of a teardrop, then transformed itself into a butterfly, then a twisting vortex narrowing to a sinuous, quivering rope of birds stretched across the twilight sky. The flock had all the synchronized precision of a marching band, but none of the rigid, rank-and-file geometry. Instead the movements were smooth, fluid, organic, as if the flock were a single organism rather than a collection of individuals. The show went on for 10 minutes, then the birds swooped low over my head with a breathy rush of wing beats and returned to the same row of trees—only to rise again moments later for another performance. The graceful aerial displays of starlings and other flocking birds have long inspired admiration and wonder. Lately they have also inspired serious work in mathematics, computer science, physics and biology. A theoretical framework for explaining the behavior of tightly clustered flocks emerged in the 1980s. The key idea, which came from computer simulations, is that purely local interactions between nearby birds are enough to hold the group together. Similar mechanisms are thought to operate in schools of fish, herds of grazing animals, swarms of insects and even crowds of people. More recent work builds on this foundation. In particular, an ambitious program of stereoscopic photography and digital image processing has made it possible to reconstruct the positions and velocities of individual birds with-
Brian Hayes is senior writer for American Scientist. Additional material related to the “Computing Science” column appears at http://bit-player. org. Address: 11 Chandler St. #2, Somerville, MA __ 02144. E-mail: ___________
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How birds (and bird-watchers) compute the behavior of a flock on the wing in large flocks. The new data suggest some refinements to the algorithms that are thought to govern the birds’ movements. The three-dimensional reconstructions have also brought some surprises about the overall shape and structure of the flocks, and show that the birds’ movements are even more delicately coordinated than casual observation would suggest. Avian Democracy
For early students of bird flocks, the most pressing questions had to do with decision making and communication. When hundreds of birds all take to the air at the same instant, how do they synchronize their liftoff? When the flock suddenly veers left or right, who decides which way to turn? Human experience suggests one solution: Appoint a leader—a conductor, a choreographer, a dictator. Leadership might be the social role of a specific individual. (Tennyson wrote of “the many-winter’d crow” that leads its flock home.) Or leadership might shift from moment to moment, as a flock on the wing follows whichever bird is currently at the front of the formation. The trouble is, biologists have found no clear evidence of either kind of leadership in flocks, and the whole idea has some deep conceptual difficulties. How do cues from the leader reach the rest of the birds? In large and dense groups, both sight and sound would be unreliable. And there’s another issue: A flock
attacked by a falcon responds instantly with evasive maneuvers; it’s implausible that the threatened birds await instructions from a leader. A more democratic vision of flock governance was proposed early in the 20th century by Edmund Selous, an intrepid English bird-watcher who kept careful notes on flocking behavior for more than 30 years. Selous rejected the notion of designated leaders as “well-nigh unthinkable—it is too ridiculous”; his alternative, however, prompts the same kind of dismissive response. Selous found the birds’ synchronized movements so uncanny that he could explain them only as a product of “thought-transference” or “simultaneous collective thinking.” In other words, the birds are telepathic. Selous was led to this extraordinary hypothesis from his assumption that flocks make decisions by some form of global consensus. The decisionmaking protocol is almost as hard to fathom as the spooky communication medium. Does each bird transmit its intention or preference to every other bird? From an algorithmic point of view, this process would be highly demanding: The N members of a flock would have to exchange almost N 2 messages. Thus the agility of the flock would depend on N, as larger flocks would necessarily take longer to make up their collective mind. Boidland
In retrospect, neither democracy nor dictatorship was a very good point of reference for understanding bird society. Both theories were swept aside dramatically in the 1980s. The key insight came not from an ornithologist but from an expert on computer graphics and animation. Craig W. Reynolds, now of Sony Computer Entertainment, wrote a program in which simulated birds—he called them “boids”—gave a convincing imi-
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Many thousands of starlings gather on winter evenings in Rome, where they make soaring display flights before roosting for the night in trees near the main railway terminal. A project called STARFLAG has employed stereophotography and computer analysis of images to determine the three-dimensional positions and velocities of birds in starling flocks. (The flocks successfully analyzed have up to about 4,000 members; some of the groups visible in this photograph are probably even larger.) The newly acquired 3D data suggest some revisions and refinements to algorithmic models that seek to explain how the birds coordinate and synchronize their movements. (Image reproduced courtesy of the STARFLAG project, INFM-CNR [Istituto Nazionale per la Fisica della Materia, Consiglio Nazionale delle Ricerche]).
tation of flocking behavior. And the boids did it without any need for leaders or thought transference. Each boid attends to a few near neighbors, ignoring the rest of the flock, and obeys three simple rules: 1. Collision avoidance: Try not to run into neighboring boids. 2. Velocity matching: Try to fly at the same speed and in the same direction as neighboring boids. 3. Cohesion: Try to stay close to neighboring boids. The rules are to be applied in the order given. That is, collision avoidwww.americanscientist.org
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ance gets the highest priority; if no collisions are imminent, then the boid adjusts its speed and direction to match the average of its neighbors’ velocities; if the velocities are already in good agreement, the boid moves a little closer to its flockmates. (Note that the third imperative is in mild conflict with the other two.) When I first read about the boid model, I was astonished that it worked. A stable state in which all the boids fly on parallel trajectories seemed like a possible outcome of the rules, but just barely so. A far more likely result, I thought, was a fragmented collection
of many small flocks, each roughly the size of a boid neighborhood. I changed my mind when I saw the boids in action and got a chance to play with implementations of the model. The flocking of boids is not a perfect simulation of bird behavior, but the resemblance is unmistakable. And the flocks are not only stable but robust. If you start the simulation with boids moving randomly, they spontaneously assemble into a flock. If an obstacle causes the flock to split, the factions eventually rejoin. What accounts for the balletic coordination of a boid flock? Although a 2011 January–February
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the two boids. Even so, it’s unexpected that distant events can exert such a powerful influence. It’s almost like thought-transference. Emergence Emerges
Three-dimensional reconstruction of a flock entails solving a difficult matching problem: Given two photographs of a flock taken at the same instant from somewhat different points of view, how do you match the featureless blob that represents a bird in one image with the corresponding blob in the other image? The red boxes in the photos above indicate five such matches; the STARFLAG group developed image-analysis tools that automate the matching process. In the four panels below the photographs, the coordinates of birds are represented as green dots, providing a model of the flock that can be reoriented in 3D space and viewed from various directions. The two views at the bottom reveal something that is not obvious from the photos: The flock has a flattened shape. (Illustration reproduced from Ballerini et al., Proceedings of the National Academy of Sciences of the U.S.A. 105:1232–1237.)
boid interacts directly only with its immediate neighbors, those neighbors interact with their own neighbors, and thus a network of indirect connections binds the whole flock together. The surprise is that these tenuous 12
links are enough to do the job. When a boid at the north end of the flock starts turning, a boid at the south end gets the signal only through several intermediaries. Admittedly, many such chains of intermediaries connect
The Reynolds boid model was part of a revolutionary change in the prevailing style of thinking about collective behavior in animals. The model was bottom-up rather than top-down, local rather than global, algorithmic rather than equational. Instead of starting with the overall form of the flock and asking how the birds could organize themselves to produce it, the model merely specified how individual birds interact with one another; the largescale structure of the flock is an “emergent property.” Reynolds was not the only one to discover the charms of such models. Frank Heppner of the University of Rhode Island had been studying bird behavior since the 1960s, including searches for leaders in flocks. In the late 1980s he began independently formulating leaderless models based on the idea of a force law acting between birds (with short-range repulsion and long-range attraction). A few years later Tamás Vicsek of Eötvös Loránd University in Budapest and several colleagues published another model, stripping away ornithological detail in a search for the simplest system that would exhibit interesting collective behavior. In essence, their model adopted just the second of Reynolds’s rules (velocity matching) along with some random noise. The Vicsek model has been applied to everything from birds to bacteria. Soon there were specialized programming languages and software systems that made it easy (and fun!) to explore such “agent-based models.” Mitchel Resnick of MIT developed one of the first of these languages, called StarLogo (which I wrote about in an earlier column, “E Pluribus Unum,” January–February 1999). Several other languages have appeared since then, and enthusiasm for agent-based modeling has spread from biology to the social sciences, finance and other areas. Moreover, the boids have come home to roost: The computational methods devised to help understand the behavior of animals in groups have come back as biologically inspired algorithms (“swarm intelligence,” “antcolony optimization”) for hard computational problems.
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Air Truth
The best computer simulations of bird flocks look wonderfully realistic— Reynolds won an Oscar for some of his flock animations—but do they tell us anything about real birds? Until recently it was hard to answer this question because so little was known about the trajectories of birds in large flocks. There were plenty of films and videos, but tracking individuals in three dimensions was not feasible. The situation has changed with new data-gathering efforts, the largest being the starflag project, an interdisciplinary collaboration extending across Italy, France, Hungary and the Netherlands. A starflag group at the University of Rome, led by Andrea Cavagna and Giorgio Parisi, has succeeded in tracing the movements of individuals in starling flocks with up to 4,000 members. The Cavagna group did not have to go far to make their observations. Every winter, vast numbers of starlings gather just a few blocks away from the university at the Termini, Rome’s main railway station. Cavagna and his colleagues set up digital cameras on the roof of a nearby building, the Palazzo Massimo. Because video recorders lack sufficient resolution, the Rome group used cameras meant for still photography and made rapid-fire sequences of exposures. Pairs of cameras were mounted 25 meters apart so that the stereoscopic disparity would provide depth cues, as in binocular vision. Each camera could record five frames per second, which is not quite fast enough for following the movement of starlings. Therefore two pairs of cameras were triggered alternately to give an effective rate of 10 frames per second. Two more cameras (making a total of six) aided in the 3D reconstruction.
To solve these problems the group built a hierarchy of image-analysis tools. The first step removes background features such as clouds, isolating the dark blobs that represent birds. Then a “blob-splitting” process breaks up overlapping bird images. In this way the photograph is reduced to an array of point coordinates in the twodimensional plane of the image. The leap into the third dimension requires combining information from multiple cameras. The basic geometric principle is well-known: An object photographed from two different points of view appears at different positions in the two images. This stereoscopic disparity provides information about the object’s range, or distance from the cameras. The complication is that the photographs include a few thousand objects that all look alike. Before calculating ranges, it’s necessary to figure out which blobs in image A go with which blobs in image B. The starflag group developed a multistage process for solving this matching problem. First a patternrecognition algorithm searches for “constellations” of points in image A whose arrangement is distinctive enough that the same points can also be identified in B, even though the constellation will be distorted somewhat by the shift in point of view. Finding about 50 such matched pairs provides enough information to approximate the geometric transformation that maps
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any point in A to the corresponding pixel position in B. The approximation is refined by exploiting images from a third camera, C, mounted close to A. The short baseline and small optical disparity make the matching problem easier for A–C image pairs. And once the A–C matches are found, they can guide the search for more A–B matches. On average, the algorithm assigned 3D positions to 88 percent of the birds in the images analyzed. Tracking a bird through time, and thereby learning its velocity as well as its position, entails matching across many successive frames rather than just the two images of a stereo pair. This is a challenging task, but the precise coordination of starling flocks helps to make it feasible. Because at any instant most of the birds are flying at the same speed and in the same direction, the average velocity vector gives a very good clue about where to look for a bird in the next frame. Flattened Flocks
The findings of the starflag program support the existing theoretical framework—the basic idea that flocks are held together by local interactions— but the results have also brought some surprises. For example, it turns out that the overall shape of starling flocks is not what it appears to be. To a casual observer, most flocks look globular; they appear to be deformed but fully rounded spheres or cylinders. But the
Birds and Blobs
Making the photos was only the first challenge; making sense of them was harder. Even with high-resolution images, a starling 100 meters from the camera is little more than a dark blob, with no individually distinguishable features. Given a pair of images that show the same configuration of birds from different points of view, how do you match up blobs that correspond to the same bird? Then how do you solve the similar problem of tracking a bird through successive frames? A further complication is that blobs often overlap. www.americanscientist.org
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Analysis of starling velocities reveals a pattern of correlations extending across the entire flock. At left are vectors representing bird velocities; at right the flock’s mean velocity has been subtracted from each vector, leaving fluctuations about the mean. (The fluctuations are actually much smaller than the velocities; the vectors have been rescaled for clarity.) The fluctuation vectors necessarily sum to zero, since the net motion of the flock has been subtracted; thus in some regions the prevailing direction is up, elsewhere it is down, and so on. The scale of these regions is comparable to the size of the flock, which indicates that velocities are correlated throughout the group. (Reproduced from Cavagna et al., Proceedings of the National Academy of Sciences of the U.S.A. 107:11865–11870.) 2011 January–February
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3D reconstructions show that the typical flock is quasi-two-dimensional: It is extended along two dimensions but squashed to a fairly thin layer along the third dimension. The average aspect ratio of length to width to thickness is 6 : 3 : 1. In general, the shortest axis is vertical, so that the flock is spread out in a thin horizontal sheet. Cavagna and his colleagues suggest a physical or physiological reason for this flight formation: Vertical movements have a higher energy cost than lateral ones, and so birds favor flight at constant altitude. What’s harder to explain is why most observers of flocks have a very different impression of their shapes and motions. The suggested explanation is a perceptual effect: Looking up at a steep angle makes it hard to distinguish between vertical motion of the flock and a component of horizontal motion directed toward or away from the observer. Another curious finding is that starling flocks have a dense outer rind and a mushy interior. The density of birds is greatest at the boundary of the flock, and it declines steadily toward the core. This is the opposite of the distribution that evolves when free-moving objects are bound together by a longrange force such as gravity; globular clusters of stars, for example, are densest in the middle and sparse at the edges. The Rome investigators discuss some ideas about why the inside-out density gradient might be useful as a defense against predators, but they do not propose a mechanism for generating the gradient. What modification of the Reynolds boid rules would account for this observation? The Rome group does introduce another, more fundamental revision of the Reynolds model. In the original simulation, a bird’s neighborhood is defined geometrically: The bird keeps track of all other birds within a certain radius of its own position. Cavagna and his colleagues propose a “topological” alternative: A bird interacts with a fixed number of nearest neighbors, regardless of their geometric distance. The number of birds comprising the neighborhood is probably six or seven. What led to this proposal was the discovery that flocks differ substantially in overall density—by a factor of two or more. If interactions were limited to a fixed radius, then birds in dense flocks would effectively have more neighbors than those in looser 14
groupings. But the observed behavior of the flocks is identical across the range of densities. Scale-Free Flocking
Of all the findings announced so far, the most intriguing have come from a study of correlations in velocity. The existence of strong correlations is hardly a surprise. After all, if the birds weren’t all flying in roughly the same direction, the flock would disintegrate. But the result is stronger than this. Subtracting the flock’s mean velocity from each bird’s individual velocity vector leaves a field of residual fluctuations—new, smaller vectors that represent the discrepancy between each bird’s motion and the average. It turns out that these vectors too are strongly correlated. The statistic called the correlation length is the distance beyond which one bird’s influence on another fades away, so that the two birds fly independently. Remarkably, the correlation length in starling flocks grows along with the flock itself, so that even birds at opposite ends remain connected. The correlations are said to be “scale-free.” What’s unusual about this situation is not just that the correlation length is greater than the interaction distance. That happens in many systems. An example from physics is a ferromagnet, in which short-range interactions between atoms produce alignments over much larger distances. But the correlation length in the magnet is not scale-free; a ferromagnet of macroscopic size breaks up into many independent domains. Why isn’t there a similar limit on the correlation length in bird flocks? One possibility is that the flock operates at a “critical point,” a set of circumstances where fluctuations extend to all possible scales of length. For a ferromagnet the critical point is a temperature known as the Curie point. In the case of bird flocks it’s not clear what would correspond to the Curie point, or even what variable would play the role of temperature. The Cavagna group explains: Scale-free correlations imply that the group is, in a strict sense, different from and more than the sum of its parts. The effective perception range of each individual is as large as the entire group and it becomes possible to transfer undamped information to all animals, no matter their distance, making the group respond as one.
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In this passage I hear an echo of Selous’s “collective thinking.” Of course no telepathy is implied; the birds communicate by ordinary physical means. And yet the outcome seems all the more impressive—and perhaps even more mysterious—for that very reason. Bibliography Bajec, Iztok Lebar, and Frank H. Heppner. 2009. Organized flight in birds. Animal Behaviour 78:777–789. Ballerini, Michele, Nicola Cabibbo, Raphael Candelier, Andrea Cavagna, Evaristo Cisbani, Irene Giardina, Alberto Orlandi, Giorgio Parisi, Andrea Procaccini, Massimiliano Viale and Vladimir Zdravkovic. 2008. Empirical investigation of starling flocks: A benchmark study in collective animal behaviour. Animal Behaviour 76:201–215. Ballerini, Michele, Nicola Cabibbo, Raphael Candelier, Andrea Cavagna, Evaristo Cisbani, Irene Giardina, Vivien Lecomte, Alberto Orlandi, Giorgio Parisi, Andrea Procaccini, Massimiliano Viale and Vladimir Zdravkovic. 2008. Interaction ruling animal collective behavior depends on topological rather than metric distance: Evidence from a field study. Proceedings of the National Academy of Sciences of the U.S.A. 105:1232–1237. Cavagna, Andrea, Irene Giardina, Alberto Orlandi, Giorgio Parisi, Andrea Procaccini, Massimiliano Viale and Vladimir Zdravkovic. 2008. The starflag handbook on collective animal behaviour. 1: Empirical methods. Animal Behaviour 76:217–236. Cavagna, Andrea, Irene Giardina, Alberto Orlandi, Giorgio Parisi and Andrea Procaccini. 2008. The starflag handbook on collective animal behaviour. 2: Three-dimensional analysis. Animal Behaviour 76:237–248. Cavagna, Andrea, Alessio Cimarelli, Irene Giardina, Giorgio Parisi, Raffaele Santagati, Fabio Stefanini and Massimiliano Viale. 2010. Scale-free correlations in starling flocks. Proceedings of the National Academy of Sciences of the U.S.A. 107:11865–11870. Couzin, Iain. 2007. Collective minds. Nature 445:715. Heppner, Frank, and Ulf Grenander. 1990. A stochastic nonlinear model for coordinated bird flocks. In The Ubiquity of Chaos (ed. by Saul Krasner), pp. 233–238. Washington, D.C.: American Association for the Advancement of Science. Resnick, Mitchel. 1994. Turtles, Termites and Traffic Jams: Explorations in Massively Parallel Microworlds. Cambridge, Mass.: MIT Press. Reynolds, Craig W. 1987. Flocks, herds, and schools: A distributed behavioral model. Computer Graphics 21(4):25–34. Selous, Edmund. 1901. Bird Watching. London: J. M. Dent & Co. Selous, Edmund. 1931. Thought-transference (or What?) in Birds. London: Constable & Co. Vicsek, Tamás, András Czirók, Eshel BenJacob, Inon Cohen and Ofer Shochet. 1995. Novel type of phase transition in a system of self-driven particles. Physical Review Letters 75:1226–1229. Vicsek, Tamás, and Anna Zafiris. 2010 (preprint). Collective motion. http://arxiv.org/ abs/1010.5017 ________
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Engineering
Bridges of the Mediterranean Henry Petroski
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he earliest bridges are generally believed to have been found structures, in that they were fortuitous arrangements of stones, felled tree trunks or hanging vines that provided a more-or-less convenient way for people to cross a stream without getting their feet wet. These chance crossings naturally led to the deliberate placing of flattish stepping stones, the manipulation of straight logs, and the rearrangement and draping of vines to gain improved footing or reach at the most desirable locations. The evolution from such elementary improvements led in time to the placing of longer stones on narrower ones to produce what are known as clapper bridges; the division of logs into timbers to produce wooden bridges with flat and level decks; and the braiding and anchoring of vines to make the main drooping cables of primitive suspension bridges. One of the earliest of bridge types used to cross wider and deeper bodies of water was the floating bridge consisting of boards placed atop a series of pontoons. This was a natural extension of the use of buoyant objects to aid swimmers, much as water wings do today. Such uses were depicted in an Assyrian relief from around 800 b.c. that shows men swimming across a river, some resting their chests on inflated animal skins. A bronze relief from about 900 b.c. shows horsedrawn chariots being led across a bridge supported on pontoons of a similar design. The men leading the horses no doubt needed to steady and calm the steeds on what appears to be a narrow and rocking crossing upon Henry Petroski is the Aleksandar S. Vesic Professor of Civil Engineering and a professor of history at Duke University. His latest book is The Essential Engineer: Why Science Alone Will Not Solve Our Global Problems. Address: Box 90287, Durham, NC 27708. www.americanscientist.org
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Living by the water often entails crossing it which there was little margin for error. As is the case with the evolution of technology generally, such bridges would come to be improved on over time by addressing their weaknesses and shortcomings. Thus, the pontoons were replaced by more substantial floating structures, with a flooring system resting on their gunwales. The sides of the bridge would in time have been fitted with balustrade-like devices not only to provide some barrier against wheels and feet slipping off the side but also to serve as blinds to shield horses from being spooked by turbulent flowing water and the movement of the structure underfoot. The written record of ancient bridges is sparse, but there are notable passages in the classical literature, some that reveal considerable detail about specific bridges and, by implication, about the historical state of the art. In his 5th-century b.c. (440 b.c.) Histories, the Greek historian Herodotus related the story of four Persian kings, including Xerxes, who ruled from 486 to 479 b.c. and invaded the Greek mainland during his reign. A critical step in that campaign was crossing the Hellespont—now more commonly known as the Dardanelles—the narrow strait that joins the Sea of Marmara with the Aegean and forms part of the boundary between Europe and Asia Minor. According to Herodotus, from the town of Abydos a double bridge was built. Each of the bridges presumably consisted of boats tied together, with Phoenicians employing ropes made
from flax on one and Egyptians using papyrus on the other. Superstitious Xerxes was livid when both bridges were destroyed by a fierce storm, and he ordered that the water, representing the god of the Hellespont, be whipped and scolded for its insolence. Those humans responsible for the failed bridges were beheaded. A new team of master builders was selected and a replacement bridge constructed. Herodotus describes with an eye for detail the design and construction of this floating bridge, which consisted of both triremes (large galleys with three banks of oars) and penteconters (warships fitted with 25 oars on each side) in considerable detail: They joined together triremes and penteconters, 360 to support the bridge on the side of the Euxine [Black] Sea, and 314 to sustain the other; and these they placed at right angles to the sea, and in the direction of the current of the Hellespont, relieving by these means the tension of the shore cables. Having joined the vessels, they moored them with anchors of unusual size, that the vessels of the bridge towards the Euxine might resist the winds which blow from within the straits, and that those of the more western bridge facing the Egean might withstand the winds which set in from the south and from the south-east. A gap was left in the penteconters in no fewer than three places, to afford a passage for such light craft as chose to enter or leave the Euxine. When all this was done, they made the cables taut from the shore by the help of wooden capstans. This time, moreover, instead of using the two materials separately, they assigned to each bridge six cables, two of which were of white flax, while four were of papyrus. Both 2011 January–February
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Some of the earliest fixed crossings in the Mediterranean region were at the junction of Europe and Asia, marked by the Bosporus Strait, the Sea of Marmara and the Dardanelles. One of the more recent additions, shown here, is the Fatih Sultan Mehmet bridge across the Bosporus at Istanbul. Its 3,567-foot main span ranks it as the 15th longest in the world today. (Photograph by Gryffindor.)
cables were of the same size and quality; but the flaxen were the heavier, weighing not less than a talent the cubit. When the bridge across the channel was thus complete, trunks of trees were sawn into planks, which were cut to the width of the bridge, and these were laid side by side upon the tightened cables, and then fastened on the top. This done, brushwood was brought, and arranged upon the planks, after which earth was heaped upon the brushwood, and the whole trodden down into a solid mass. Lastly a bulwark was set up on either side of this causeway, of such a height as to prevent the sumpter-beasts and the horses from seeing over it and taking fright at the water. It is most likely that a bridge of such magnitude had evolved from smaller ones and that many of its features were the result of disappointing experiences with prior bridges. Thus, the use of both flax and papyrus cables on the same structure may have been in direct response to the separate use of the different (and fewer) cables on the two earlier bridges that failed. The seemingly unnecessary steps of cover16
ing the wooden planks with brushwood and that with earth and then compacting it all down may have been introduced after animals shied from walking on the bare (and noisy) boards of earlier bridges. Dirt resting directly on boards would not likely have stayed in place for very long; putting down brushwood first would have made the dirt covering more durable. And the use of a bulwark, to keep the pack animals and horses from seeing and being frightened by the water, also suggests that the lesson had been learned the hard way from the behavior of the beasts on earlier bridges on which the water was not shielded from view. Herodotus’s recounting not only has the reader believing that the historian actually saw such a bridge but also that he was describing a structure that had many unrecorded precedents. (Julius Caesar, in his 1st-century b.c. Gallic Wars, describes with similar attention to detail a bridge resting on inclined piles and designed to cross the Rhine.) Bridging the Golden Horn
On the more northern side of the Sea of Marmara, the Bosporus Strait connects it with the Black Sea. The Bosporus also forms one section of the boundary
between Europe and Asia, and modern Istanbul is located on both sides of the strait. The Golden Horn, an arcing arm of the Bosporus that forms a historic natural harbor on the European side, also divided the older parts of Istanbul into Muslim and nonMuslim districts. Bridges have been built and proposed across the Golden Horn since at least the 6th century of the modern era. The oldest recorded bridge across the divide was a floating structure built during the Turkish siege of the city in 1453. In the early 16th century, Leonardo da Vinci was asked to design a permanent structure to span the harbor, but his ambitious plans for an unusual and record-long arch spanning of the order of 1,000 feet remained unrealized for five centuries. (It was only in 2001 that a scaled-down version of the artist-engineer’s Golden Horn Bridge was finally erected—in Oslo, Norway.) One of the most storied locations for a bridge across the Golden Horn was at the narrow part of the harbor near its mouth, where the old Muslim district sits across the water from the non-Muslim district known as Galata. As was fitting for a region associated with the exploits of Xerxes, pontoon or floating bridges began to be put in
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place at this location in the 19th century. The first Galata Bridge was completed in 1845 and was known as New Bridge, to distinguish it from an 1836 linkedpontoon structure located farther from the harbor mouth. The 1845 span was replaced in 1863 by a new wooden Galata Bridge, built in preparation for the coming of Napoleon III to Istanbul. Wooden bridges generally do not last very long, however, and in 1875 a third Galata Bridge was opened. Its roadway floated on 24 pontoons, and people crossing it must have felt it move with the currents and waves. Pontoon bridges were employed because at the time it was believed that the seabed was not sufficiently firm to support the weight of a major structure. What is considered the first modern floating bridge at this location and the most famous of the ones connecting Old Istanbul to Galata was completed in 1912. It consisted of 50 steel pontoons hinged together to cross the deep harbor. This familiar Galata Bridge played a romantic role in Turkish literature, being at least mentioned in most novels of its time, and it was much photographed. Unfortunately, in 1992 a fire broke out in one of the wood-framed restaurants constructed between the tops of the pontoons and the underside of the roadway, and the blaze and the heat it gave off caused considerable damage to the historic bridge structure, including sinking six of its pontoons. These were eventually raised from the water, and the damaged structure was towed up the Golden Horn to be modified for service at a different part of the harbor. A new crossing was quickly designed and constructed at the location of the previous Galata Bridge. This time, taking advantage of progress in bridge-building techniques, the structure was founded on piles driven deep into the soft seabed. The New Galata Bridge, which opened in 1993, also has a world-class bascule span. This drawbridge portion carries pedestrians, motor vehicles and trams across the historic harbor, but even this newest Galata Bridge has not been without its problems. Its moveable leaves soon developed cracks and became distorted, problems traced to the moving parts having had a natural frequency close to that of the hydraulic system by which they were operated. There were also concerns that the natural frequencies of the structure were close to those www.americanscientist.org
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The earliest record of an intentional bridge comes from Herodotus’s Histories, in which he describes a bridge built across the Dardanelles in the 5th century B.C. in order for Xerxes to attack Greece. Other notable Mediterranean bridges include those across the Bosporus and the Rion-Antirion Bridge at the Strait of Corinth. Fixed links under construction or proposed include those across the straits of Messina and Gibraltar.
of earthquakes expected in the region, prompting modifications. Floating bridges are no longer very common in an age of high-profile signature structures that also allow for high clearances, but they continue to be used in locations demanding long crossings over deep water, where the construction of foundations and piers would be dangerous and expensive. Precast-concrete floating bridges have been used since 1940 around Seattle, Washington. And since the 1990s, Norway, noted for its deep fjords, has also been using floating bridges employing precast-concrete pontoons. Limited Options
The evolution of bridges continues to be fueled by experience, good and bad. What does not work well becomes modified, if not extinct; what works well survives and thrives. Thus a limited number of bridge types continue to be employed, especially for long crossings. The suspension bridge remains the only practical one for very long spans requiring high clearance, in spite of the fact that there have been notable failures of the form. The modern suspension bridge—one that used iron rather than vines or natural-fiber ropes for its principal support—dates from the early 19th century, but it did not have a propitious debut. Many early bridges were damaged, if not outright destroyed, by the wind. There were few practical alternatives, however, so
the form persisted. The engineer John Roebling studied the failures of suspension bridges and concluded that the spans could indeed be designed to survive storms. His 1854 bridge across the Niagara Gorge not only withstood the force of the wind but also became the first suspension bridge to carry railroad trains. Roebling’s masterpiece, the Brooklyn Bridge, stands today as a monument to his insights. Unfortunately, the lessons that Roebling learned became lost over the course of the following century, and this historical amnesia led to the use of aesthetically striking but structurally flexible bridge decks, a trend that culminated in the infamous failure of the Tacoma Narrows Bridge in 1940. That incident prompted a revisiting of the aerodynamic action of the wind on bridge decks, and new thinking about their features resulted. American designers returned to deep steel trusses to stiffen their decks, whereas the British came to employ box girders with wing-like extensions cantilevered out from either side. This novel deck design was introduced by the design firm of Freeman Fox & Partners in the 1966 Severn Bridge between England and Wales and was exported to the Continent. Two examples of these deck designs exist in the pair of world-class suspension bridges that span the Bosporus at Istanbul and provided the first fixed crossings between Asia and Europe 2011 January–February
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Galata Bridge crosses Istanbul’s Golden Horn. Several floating bridges have been built there, including this 1875 version photographed in the late 1800s. (Photograph from Wikimedia Commons.)
since Xerxes’ pontoon bridge across the Hellespont. Collectively known as the Bosporus Bridges, they are among the top 20 longest suspension bridges worldwide, as measured by their main span, which is that between the towers. When completed in 1973, what is now sometimes referred to as the First Bosporus Bridge was the longest suspended span outside the United States and the fourth longest in the world, exceeded only by the Verrazano Narrows (4,260-foot main span), Golden Gate (4,200 feet) and Mackinac (3,800 feet) bridges. Currently, the 3,524-foot main span of the First Bosporus Bridge puts it in 17th place among all suspension bridges, just before New York’s George Washington Bridge, which has a main span of 3,500 feet. As has been the case with so many bridges, on opening day the roadway of the Bosporus was given over to pedestrians. The footfalls of tens of thousands of them caused the bridge deck to develop a wavelike oscillation. Those on the bridge were instructed to remain stationary until they were allowed to walk off the span in groups of limited numbers. Ironically, the novel hollowbox deck structure had been introduced by Freeman Fox in response to the extreme flexibility that American bridges had exhibited in the late 1930s and that 18
led to the Tacoma Narrows collapse. Pedestrians were eventually banned from the Bosporus Bridge not because of the behavior of its roadway but because of its 146-foot height, which attracted a large number of people wishing to jump to their death, a phenomenon that has plagued many a high bridge. (When the Irish rock band U2 played in Istanbul in 2010, its lead singer and international activist Bono was allowed to walk across the bridge with some Turkish dignitaries, an event that made the normally congested roadway even more so.) The existence of a bridge also promotes commerce and economic vitality—and often the need for another bridge to handle the associated increased traffic. A new bridge attracts traffic and promotes growth, which in turn creates the demand for another bridge. The Second Bosporus Bridge, completed in 1988, is officially named the Fatih Sultan Mehmet Bridge, after the Ottoman Empire leader who took Istanbul in 1453. The structure’s 3,576foot main span places it 15th in the list of the world’s longest spans today. As close as they are to each other in size and overall structural appearance, the two Bosporus bridges are distinguished from each other by the means by which the deck is hung from the
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main suspension cables. In the first bridge, the suspenders are inclined, whereas in the second they are vertical. Inclined suspenders were introduced by Freeman Fox in the Severn Bridge and were used also in England’s Humber Bridge to damp out undesirable deck motions, but problems with metal fatigue caused a rethinking of their use. Hence, inclined suspenders were not used in the Second Bosporus Bridge. (The fact that the first bridge vibrated under a huge opening-day crowd may also have influenced the change of hanger geometry.) Among the most distinguishing features of John Roebling’s Brooklyn Bridge, which has the traditional vertical suspenders, are its inclined stay cables, which he felt were necessary to steady the deck of a suspension bridge against the wind. Early 20thcentury engineers saw the stay cables as redundant, however, and no major suspension bridge built subsequently included them. If those inclined cables are indeed redundant on the Brooklyn Bridge, then it is natural to ask if its main suspension cables (and the suspenders between the deck and main cables) might also be viewed as redundant. Could a bridge be designed with stay cables alone? The answer is yes, and this is in fact the principle behind the so-called cable-stayed bridge, which appeared in its modern form in the latter part of the 20th century. Westward in the Med
One striking example of a cable-stayed bridge spans Greece’s Strait of Corinth between the towns of Rion and Antirion, thus linking the southern section of the country, known as the Peloponnesus, with the mainland and reducing travel time by a factor of 10 over what it took by ferry. The Rion-Antirion Bridge, which is officially named the Harilaos Trikoupis Bridge, after the Greek prime minister who more than a century ago first proposed a fixed crossing, was completed in 2004, four months ahead of schedule but just in time for the Olympic torch to be carried across the bridge on its way to Athens. The bridge’s stay cables radiate from four reinforced-concrete pylons and support a steel-and-concrete composite deck to make what was the longest cable-stayed bridge in the world at the time of its completion. Because the area experiences high seismic activity, special attention had
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Harilaos Trikoupis Bridge crosses the Strait of Corinth between the towns of Rion and Antirion, linking the northern part of Greece with the Peloppenesus. It was completed in 2004 just in time for the Olympic torch to be carried across on its way to Athens. It was the world’s longest cable-stayed bridge at the time of its completion.
to be paid to how the bridge deck was supported. It does not rest directly on the pylons but is suspended above their base and allowed to move freely within the cage of their legs. In the event of an earthquake, the deck is thus designed to sway, but its pendulum-like movement will be limited by the presence of damping devices and structural fuses. In addition to seismic considerations and the challenge of being built in deep water, the Rion-Antirion Bridge also had to be designed to withstand high winds and the impact of a large tanker. In 2005, the $900-million bridge was named the Outstanding Civil Engineering Achievement of the year by the American Society of Civil Engineers. Fixed Links to Come
There are plenty of other places throughout the Mediterranean region that could benefit from the existence of bridges, and they have long been the object of engineers’ dreams. One such location is the two-mile-wide Strait of Messina, which separates Sicily from mainland Italy. Ideas for a bridge across the strait date from Roman times, when a floating bridge was proposed. While it is true that wider bodies of water have been bridged, the great depth of the Messina strait made it imperative that any bridge design for the location contain as few piers as possible in the water. In the mid-20th century, David www.americanscientist.org
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Steinman, who designed the mighty suspension bridge that since 1957 has spanned Michigan’s Straits of Mackinac, thus uniting the state’s upper and lower peninsulas, proposed a suspension bridge across the Messina Strait. His concept would have required towers founded in water 400 feet deep, making the project prohibitively expensive. In 1969, the German bridge engineer Fritz Leonhardt put forth a cable-stayed design of unprecedented proportions. Neither of these was built, but that did not discourage further proposals. In 1986, the state-sponsored company Stretto di Messina released a study report on the feasibility of three crossing options: a suspension/cablestayed hybrid bridge, a tunnel bored beneath the sea bottom and a floating tunnel. This last does not literally float on the water but is anchored to the seafloor and by its buoyancy “floats” at such a depth that it poses no obstacle to shipping. The hybrid solution was recommended, provided that its towers were land-based. This meant that the main suspended span would have to reach in a single bound all the way across the wide strait. As an analogous early design did at the strait connecting San Francisco Bay and the Pacific Ocean, the Italian hybrid design evolved into a pure suspension bridge. However, rather than having a traditional stiffening truss like that on the Golden Gate
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Bridge, the bridge at Messina will have a steel-airfoil deck akin to those of the Bosporus suspension bridges, but with open space between the vehicleand rail-carrying components of it. The Messina Strait bridge project was on-again-off-again for years, it being cancelled in 2006 but revived again in late 2009 when the Italian government pledged 1.3 billion euros toward the projected total cost of 6.1 billion euros. The expected completion date is 2016, economic conditions allowing. Still more ambitious Mediterranean dreams include the bridging of the Strait of Gibraltar, thus connecting Morocco and Spain—Africa and Europe—with a fixed link. At the likely site of such a span, the water is of the order of 15 miles wide and can be 1,500 feet deep, and more. These distances and depths provide unprecedented challenges for bridge builders, who have had to come up with imaginative ideas. Among them is a combination suspension and cable-stayed bridge of many spans, perhaps being supported by floating towers, thereby making use of offshore oil-drilling-rig technology. Other proposals have included buoyant tunnels. Whether a Gibraltar bridge or tunnel will be realized in coming decades or centuries will depend on many factors, not least of which will be international politics and global economics. Bibliography Andrews, E. A. 1873. C. Julius Caesar’s Commentaries on the Gallic War, with a Dictionary and Notes, 58th edition. Boston: Houghton, Mifflin. pp. 201–203. Arda, Tevfik Seno, Nesrin Yardimci and Oguz Eyrekci. 1996. Rehabilitation of two floating bridges, Turkey. Structural Engineering International 1/96:17–18. Bozdag, E., E. Sunbuloglu and H. Ersoy. 2006. Vibration analysis of new Galata Bridge— experimental and numerical results. Computers & Structures 84:283–292. Brown, David J. 1993. Bridges. New York: Macmillan Publishing Co. pp. 162–163. de Camp, L. Spague. 1963. The Ancient Engineers. Garden City, N.Y.: Doubleday & Co. Herodotus. 440 b.c. The History of Herodotus, translated by George Rawlinson, Book VII. http://classics.mit.edu/Herodotus/ history.7.vii.html#629. _____________ Hodges, Henry. 1992. Technology in the Ancient World. New York: Barnes & Noble. Sansal, Burak. 2010. Galata and the Galata Bridge. All About Turkey, __________ http://www.allaboutturkey.com/galata.htm. _________________ Watanabe, Eiichi. 2003. Floating bridges: past and present. Structural Engineering International 13, 2:128–132. 2011 January–February
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Marginalia
The Biology of What Is Not There Robert L. Dorit
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nderstanding the living world seems challenge enough for biologists. Technological advances have produced a cascade of data—from detailed genome sequences to the sophisticated satellite imagery that documents the planet’s ecosystems—but our ability to make sense of these data still lags far behind their acquisition. With such a backlog, the idea that we might want to think about objects that are not real seems, frankly, capricious. Yet without thinking about lifeforms that never were, we cannot fully understand the life forms that do exist. Questions about absence lie at the very core of evolutionary biology: Is the living world we behold the only possible outcome of the evolutionary forces that produced it? Or can we imagine, instead, different unfoldings, of which this is but one? The one actual unfurling of the tree of life, of course, places restrictions on our capacity to address this question. I would argue that there are nonetheless ways of posing such queries that may prove productive. Shells Imagined
The most accessible example of how to examine the shapes of the possible comes from work on shell forms carried out in the 1960s by American paleontologist David Raup and his collaborators (see the first figure). Shell shapes are beautiful; they are also geometrically well behaved and can be described relatively easily in mathematical terms. The mathematical model of shell shape, at its most basic, includes the rate at which a shell grows around its central axis, the rate at which it Robert L. Dorit is an associate professor in the Department of Biological Sciences at Smith College. His work focuses on the experimental evolution of molecules and bacteria and on the design of novel antibiotics. Address: 435 Sabin-Reed Hall, Clark Science Center, 44 College Lane, Northampton, MA 01063. E-mail: _________
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Is it only natural selection that guides the shapes seen in nature?
descends down that same axis and the rate at which the shell opening expands as its architect grows. With these three parameters we can depict a three-dimensional shape space: Any point in that space defines a single shell shape that may or may not occur in the living world. Real shell-bearing organisms are varied, abundant both in the current biosphere and in the fossil record, and their shapes can be plotted onto the shape space we have defined. When we do so, the pattern is striking. Certain regions of the cube, shown in color, are densely occupied, but most of the cube is uninhabited. The challenge of understanding the distribution of biological objects in shape space thus consists of two separate, but interrelated, problems. The first of these problems involves the definition of the space of possibilities. For snail shells, we are fortunate, because the shape is mathematically tractable (a logarithmic spiral is a reasonable first approximation). The shape also involves a limited number of variables (in this case, three, which allows us to depict the space as a three-dimensional cube). For other biological shapes at other scales, defining the shape space may be considerably more challenging. How, for instance, do we define the space of all possible protein or RNA shapes? What mathematical expression will capture all of the possible architectures of tree shape? Not only are these
spaces likely to be of a higher dimensionality, making them harder to depict, but the underlying mathematical function that can generate the shapes is likely to be far more complex. The second problem with understanding shape distributions involves mapping the real objects of the world onto the shape space that we have constructed—and then accounting for the distribution of these realized forms. And it is here that we find an astonishingly consistent result. In every case studied, the distribution of realized shapes is nonisotropic: Some parts of the cube are densely populated with realized shapes, whereas others are virtually, if not entirely, empty. Such patterns in biology demand an explanation. What is this strange occupancy of shape space at all scales telling us about the forces that give form to the living world? Invoking Selection
The temptation to attribute the occupancy of shape space to the action of natural selection is almost irresistible. In this optimalist light, the occupancy problem is easily dismissed: What is there is what works; what is not, doesn’t. Yet this easy solution may be based on a set of problematic assumptions. To be sure, the objects of the real world—shell shapes in our example— do function effectively in their environment, or natural selection would have made short work of them. The nautilus shell is a stunning example of how propulsion and buoyancy can be elegantly balanced, and biologists and naval engineers alike justly admire its shape. The barnacle shell has indeed evolved a shape that enables its tenant to survive the pounding of the waves, and the rising and falling of the tides. But the fact that natural selection acts incessantly to shape the natural world does not mean that anything that we do not see has been tested by natural
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selection and found wanting. What that formulation assumes is that every corner of shape space is accessible, that every conceivable shape in our cube has in fact been tried—which is to assume too much. Evolutionary theory, especially in its Anglo-American formulation, has traditionally favored the idea of natural selection as the driving force that shapes living form. Natural selection is indeed a powerful chisel, but a complete theory of evolution also needs to take into account the material being chiseled. The occupancy riddle will not be solved until we think about how organisms are actually built, and until we give history its proper due as an architect of form. Constructionist explanations for the occupancy of shape space acknowledge that not all corners of shape space are equally accessible. Under this rubric, the occupancy of shape space derives (at least in part) from the consequences of how biological forms are constructed. Organisms have ontogenies, and the way they develop from a fertilized single cell into a final adult form has implications for the resulting shape. Thus, to stay with our shell-shape example, it is unlikely, if not impossible, for the opening of the shell (where new material is deposited) to decrease in size as the animal matures. Organisms tend to get bigger as they mature. Even though it is possible to model a logarithmic spiral whose leading edge grows and then shrinks, that excursion in shape space appears to be inaccessible to real organisms. Importantly, this inaccessibility is not due to the fact that such a shape would not function and thus would be eliminated by natural selection. Instead, we do not see it as a realized shape because, given the rules that govern shell construction, it occupies forbidden territory. Given how shapes are made, certain among them cannot even show up to participate in the struggle for existence. Proteins too have ontogenies, dictated by folding rules. And similar forbidden zones in shape space exist at the molecular level. Knots, for example, are notoriously scarce in proteins, for reasons that flow both from the chemical character of the amino-acid components of proteins and from the mechanisms that govern protein folding. (In the interest of full disclosure, I should note that until fairly recently
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The shape space of possible shell shapes is shown as a grey cube, with the areas that are actually occupied by real shells—either extant or fossil—in color. Each color corresponds to a different group of shelled animals: blue for gastropods, yellow for bivalves, green for cephalopods and orange for brachiopods. The shapes that ring the cube correspond to particular points within the shape space, and include both forms that exist in nature and others that have never been seen. (Image adapted from D. M. Raup, 1966, Journal of Paleontology 40:1178; shell shapes drawn in Mathematica.)
we thought knots to be a virtually impossible geometry for real proteins to adopt. We were wrong. They are rare, but not impossible.) Following the Rules
In our search to account for the occupancy of shape space, we have much to gain by paying closer attention to the rules and mechanisms that generate form. Simultaneous progress in computational methods and developmental biology repeatedly leads to the same conclusion: Simple rules can give rise to enormously complex forms. A graphic example, first described by British physicist and mathematician Stephen Wolfram, is shown in the second figure. In this computer simulation, a simple set of generating rules
(such as “branch out into 3 [or 2 or 4], increase the branching angle by 15 degrees, repeat”) gives rise to an array of leaflike forms. These forms are striking in their variety. Note, too, that every shape is discrete and does not appear to blend with an adjacent shape: The generating rules themselves populate shape space in characteristic ways, overstuffing certain parts of it while leaving others nearly deserted. By attending to the construction of biological forms, we can begin to appreciate just how much pattern and structure can arise before natural selection even has a hand in the process. Provocative as they are, however, these relatively simple simulations need to be interpreted with caution: They are not meant to simulate the 2011 January–February
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A variety of leaf shapes are generated by a set of simple underlying rules, in this case a rule specifying that every branch split into three branches (except for the bottom two rows, where they split into four and two branches respectively). The angle between the branches increases by 15 degrees at every iteration across the figure, allowing for denser packing from right to left. (Image adapted from Stephen Wolfram, A New Kind of Science, 2002, Wolfram Media Inc., p 402.)
actual biological mechanisms of leaf development. We have yet to elucidate fully the actual dynamics that determine leaf shape. Similarly, we need to remember that the developmental process—the biological counterpart of the computer program that created these leaf shapes—itself evolves. Indeed, the evolution of developmental programs has resulted in the opening up of regions of shape space that might previously have been inaccessible. For instance, take the Cambrian explosion some 600 million years ago. Changes in the rules of construction, coupled with changes in the geochemistry of the oceans, suddenly allowed certain groups of marine organisms to make hard shells. Whole new dimensions of shape space abruptly opened, 22
and the diversity of organisms on this planet was forever changed. Rediscovering History
Although the constructionist perspective enhances our ability to account for the distribution of biological objects in shape space, it lacks an acknowledgment of the role that history plays in the filling of shape space. At its most basic, history matters because evolution often works by composing variants on a theme. As a result, once a functional shape evolves, the adjacent shape space is most likely the first to be fully explored. This tendency to remain in the shape neighborhood of one’s ancestors is further enforced if the existing shape is surrounded by less-functional alternatives. Evolution
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will not cross through less-fit alternatives even if better-functioning alternatives lie within view. The extent to which history controls the distribution of realized shapes also depends on just how easily one shape can be transformed to the next. In our shell example, we can safely claim that cone shells, in terms of transformation, are conservative. They give rise to other cone shells, both from one generation to the next and over evolutionary time. The corner of the tree of life represented by the genus Conus is bushy indeed, with over 3,000 named species, each of them crowded into a distinctive zone in shell space. But for shapes at other scales—the shape of folded RNAs, for instance, or the shape of proteins—a few changes in the sequence may suffice to cause a flip from one location in shape space to a completely new location. Perhaps if every lineage had world enough and time, if the tree of life had an infinity to explore shape space, it would eventually discover every successful form that could be built given constructionist constraints. But history dictates that because the evolutionary life of most lineages is brief, many paths and shapes remain unexplored. Having defined the universe of the possible, we will have to populate it with the actual. We will need statistical approaches to determine whether there are over- and under-populated zones beyond what we would expect from sampling alone. We will need to flesh out the consequences of the ways in which living form is built and the constraints imposed by the materials of life. We will need to elucidate the role of time and history in shaping shape. And only then will we be able to invoke the sculpting power of natural selection. Yet daunting as the occupancy problem is, the nonisotropic distribution of realized forms appears both universal and independent of scale. Such regularity in biology is strangely beguiling. When you next look out at the stars, notice how some parts of the night sky are teeming with stars, whereas others seem comparatively dark. This is no optical illusion. At all scales, and for all of the classes of objects that astronomers can identify—stars, galaxies and constellations—the universe, too, is nonisotropic. The variability of the heavens, like the variety of living things, underlies much of their beauty.
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Ethics
A Troubled Tradition It’s time to rebuild trust among authors, editors and peer reviewers David B. Resnik
B
y the mid 1700s, editors at the world’s first scientific journal had a problem on their hands. Since its inaugural issue in 1665, the Philosophical Transactions of the Royal Society of London had published many outstanding scientific papers, including such classics as Isaac Newton’s experiments with prisms. But some authors had begun to submit works of fiction and rambling speculative essays. To maintain standards of quality, the editors of Philosophical Transactions launched a system of peer review to evaluate manuscripts before publication. Two centuries went by, however, before the system really caught on. In the mid 20th century, increased specialization, government support for research, and competition for journal space compelled editors to seek assistance from experts. Today, peer review is an essential part of scientific publication and is also used to evaluate manuscripts, grants and academic careers. In publication, peer review serves two distinct functions: It ensures that work is published only if it meets appropriate standards of scholarship and methodology, and it helps authors improve their manuscripts. The process, familiar to many American Scientist readers, begins when authors submit a manuscript to a journal, often with a list of suggested reviewers and a list of scientists who should not see the work. The journal editor sends papers of interest to members of the editorial board or outside experts who review the work for free. David B. Resnik is a bioethicist at the National Institute of Environmental Health Sciences. He received a Ph.D. in philosophy from the University of North Carolina, Chapel Hill, and a J.D. from the Concord University School of Law in Los Angeles in 2000. Address: P.O. Box 12233, Mail Drop CU 03, Research Triangle Park, North Carolina 27709. E-mail: ____________
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intentional abuse for personal gain. If scientific publications are to remain a reliable record of knowledge and progress, editors and reviewers must actively cultivate high ethical standards. The Importance of Trust
The world’s first scientific journal, the Philosophical Transactions of the Royal Society of London, pioneered a system of peer review to help editors evaluate manuscripts. (Image from The Online Books Page, http://onlinebooks. library.upenn.edu.) ___________
These referees assess the manuscript for originality, importance, validity, and clarity. They also advise the editor about the manuscript’s overall merit and provide written comments—usually anonymously—for the authors. Finally, the editor decides to publish, reject or request revisions to the manuscript. Although it is hard to imagine how science could progress without independent evaluation of research, peer review is an imperfect system, fraught with questions of bias, efficacy and ethics. At each step of the process, there are opportunities and temptations for reviewers to go astray, and these can take many forms, from simple negligence to
It seems that most scientists have a story or two about suspected unethical behavior among reviewers. As a beginning assistant professor, I submitted a paper on scientific methodology to a prestigious philosophy journal. The review took a long time—over a year— and when I finally got a decision, the paper was rejected with little comment. A couple of months after that rejection, a paper very similar to mine appeared in the same journal. The article did not plagiarize my work word-for-word, but it defended a similar thesis using many of the same arguments. I suspected that the author had served as a referee for my paper and had delayed his review to prevent my article from being published—or perhaps that he had pilfered my ideas. It is possible that the author of this competing paper had independently arrived at conclusions and arguments similar to mine, and that he had submitted his work to the journal before I did. But I had no way of knowing whether this was so. In the end, I was left with a bitter taste in my mouth and I lost some trust in the integrity of peer review. It can be hard to determine when a reviewer has abused his or her position. Unscrupulous referees may plagiarize a submitted manuscript, breach confidentiality, delay the review process in order to stifle competitors, use data or methods disclosed in a manuscript without permission, make personal attacks on the authors or require unnecessary references to their own publications. Incidents such as these violate the foundation of trust that is essential to
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successful evaluation of scientific manuscripts. Authors, editors and reviewers must rely on one another to fulfill their roles with honesty, transparency, confidentiality and professionalism. Absent such trust, the system simply doesn’t work: Authors and editors may ignore reviews that they think are biased or incompetent. Or, fearing that their ideas could be stolen, authors may withhold information necessary to repeat experiments—thereby compromising a key function of scientific publication. Editors who do not trust reviewers to work carefully and disclose conflicts of interest may ignore their comments or delay publication by seeking other reviewers. Disillusioned reviewers may submit careless evaluations or refuse to review manuscripts. Finally, authors who violate reviewers’ and editors’ trust by submitting fraudulent results
can create lasting discipline-wide difficulties for other researchers. To promote trust among authors, editors and reviewers, it is essential that all parties follow ethical standards. Most policies and scholarship related to scientific publication focus on the ethical duties of authors, but at least two sets of important guidelines do address reviewers. The International Committee of Medical Journal Editors recommends that peer review be unbiased and that journals publish their peer-review policies. The Committee on Publication Ethics (COPE), a nonprofit organization of journals, publishers and individuals, has developed guidelines that address confidentiality of peer review, protection of intellectual property, fairness and conflict-of-interest management. Some standards of peer review for editors and referees, recognized by COPE and leading authorities on research integrity, are: Confidentiality: Maintain confidentiality throughout the review process. Respect for intellectual property: Do not use authors’ ideas, data, methods, figures or results without permission. Fairness: Avoid biases related to gender, nationality, institutional affiliation and career status. Professionalism: Read manuscripts carefully, give constructive criticism, avoid personal attacks and complete reviews on time. Review only manuscripts that you are qualified to review. Conflict-of-interest management: Disclose personal, professional or financial interests that could affect a review and avoid reviewing an article if a conflict of interest could compromise judgment. If referees followed these guidelines faithfully, I suspect there would be very few setbacks in peer review. AP Photo/Lee Jin-man
This South Korean patient hoped to benefit from stem-cell research that was published in Science but that was later found to be fraudulent. The affair prompted editors to scrutinize high-impact papers more closely before publication. Inset: A stem-cell image that was erroneously duplicated in one of the fraudulent studies. (Reprinted from Hwang, et al. 2005 with permission from AAAS.) www.americanscientist.org
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Problems
Despite efforts to encourage professionalism among reviewers, troubles persist. One of the best-documented issues is inefficacy: Reviewers may miss errors, methodological flaws or evidence of misconduct. To measure reviewers’ ability to catch errors, Magne Nylenna of the Journal of the Norwegian Medical Association and his colleagues created two inauthentic manuscripts with obvious methodological flaws such as inappropriate statistical tests. They sent the papers for review and graded reviewers on the number of flaws they caught. The average score was only 1.7 out of 4,
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and more than one-third of the reviewers provided no comments on methodology at all. Nylenna’s results were not anomalous. In a similar study led by Fiona Godlee of the British Medical Journal, reviewers discovered, on average, only 2 out of 8 errors introduced into manuscripts. These studies did not determine why reviewers missed so much, but they may have simply read the manuscripts carelessly. Falsification and fabrication are problems that reviewers shouldn’t have to worry about—but in reality, they must remain alert. One of the most famous examples occurred in 2004 and 2005, when South Korean researcher WooSuk Hwang and colleagues published two papers in Science claiming to have developed human embryonic stem-cell lines that were genetically identical to patients’ cells. The work would have been a breakthrough in regenerative medicine, but in June 2005, a whistleblower declared that some of the data were fake. Eventually, a university investigation found that Hwang had fabricated data in both papers, which were then retracted. Whether editors and reviewers should have spotted evidence of Hwang’s misconduct is unclear—but without access to raw data, detecting fraud is notoriously difficult. Indeed, the incident prompted the editors of Science to scrutinize high-profile papers more closely, requiring authors to provide original data and examining digital images more carefully. Even when reviewers do catch flaws in a manuscript, they may not all agree in their assessments. In one recent study, Richard Kravitz of the University of California, Davis, and colleagues examined reviewer recommendations for more than 2,000 manuscripts submitted to the Journal of General Internal Medicine. For editors to publish work with confidence, reviewers should ideally agree about whether to accept or reject a manuscript—but in fact, they concurred only slightly more often than if they had made their decisions by coin toss. Multidisciplinary research can cause particular confusion because reviewers from different disciplines may accept different methodological standards. In these cases, editors may feel the need to seek additional reviews, potentially delaying publication. A more subtle but equally pervasive problem is reviewer bias. A reviewer’s evaluation can be influenced by an author’s institutional affiliation, national2011 January–February
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incompetent biased unnecessary references personal attacks delayed review breached confidentiality used ideas, data, methods without permission 0
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Biomedical researchers at the National Institute of Environmental Health Sciences have experienced an array of ethical problems with peer review. Well over half of those surveyed in 2006 said they had received at least one biased or incompetent review. More malicious ethical problems such as breach of confidentiality were also disturbingly common.
ity, gender or career status, or by the reviewer’s own financial or professional interests. For example, a referee might be more likely to give a favorable review to a friend than to a competitor, or to favor a well-known researcher from a prestigious institution over a less familiar researcher. Although specific allegations of bias are difficult to prove, the phenomenon has been documented in systematic studies. In a 1982 study, for example, Douglas Peters and Stephen Ceci selected 12 previously published psychology papers by authors from prestigious institutions, then resubmitted the papers to the same journals using fake author names and institutions. Of nine journals that sent the papers for review, eight rejected them due to poor quality. The results suggest that the original reviewers’ favorable evaluations may have been influenced by the prestige of the authors or their institutions. Although the sample size was small and the experiment lacked controls, larger trials with alternative forms of peer review also suggest that referees are influenced by their assumptions about authors. More malicious transgressions, such as intentionally delaying reviews, are less well documented. To fill this gap in the literature, my colleagues, Shyamal Peddada and Christine Gutierrez-Ford, and I conducted a survey in 2006 to ask scientists about a range of problems in peer review. The respondents included 220 postdoctoral researchers, staff scientists, principal investigators and technicians working in 22 different biomedical disciplines at the National Institutes of Environmental Health Sciences (NIEHS). They were about 54 percent male and 44 percent female; 2 percent did not specify gender. On average, they were 42 years old and had about 35 publications each. 26
Reviewer incompetence was the most common problem this group reported: More than 60 percent of respondents said they had encountered at least one reviewer who did not read an article carefully, was not familiar with the subject matter or made mistakes of fact or reasoning in the review (see the chart above). About half said a reviewer was biased. Other common problems were that reviewers required unnecessary references to their own publications or made personal attacks in reviews. About 10 percent of respondents said a referee delayed the review so that he or she could publish an article on the same topic. Rarer, but still troubling, were reports that reviewers had breached confidentiality or used ideas, data or methods without permission. An author’s age and number of publications were both positively associated with experiencing an incompetent or biased reviewer—perhaps because a researcher who has published more papers has had more opportunities to encounter reviewers whom he or she views as biased or incompetent. Scientists who are well established in a field may also be less open to criticism from reviewers and therefore be more likely to perceive reviews as inadequate. This study did have some limitations. The questionnaire asked for respondents’ experiences, but we did not attempt to confirm whether alleged problems actually occurred. For example, some reports of reviewer bias might simply reflect the authors’ dissatisfaction with a referee’s comments. We also did not attempt to determine how frequently respondents experienced the problems they reported. Finally, our sample of biomedical researchers working at a government institution may or may not reflect the experiences of other
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researchers at other institutions or in other disciplines. The study does, however, provide some of the only empirical evidence that scientists regularly experience a range of ethical problems with peer review. To expand upon our results, future research should examine the prevalence and significance of such problems in peer review, as well as potential causes—such as inadequate training, or competition for status or funding. This research might take the form of focus groups, interviews, and surveys with editors, reviewers and authors. The results could guide both policy development and educational initiatives. Alternative Forms of Peer Review
Some journals and conferences have adopted or tested alternative forms of peer review. One common alternative, double-blind review, could serve to reduce reviewer bias because neither authors nor reviewers know each other’s identities or affiliations. Another alternative is unblinded (or open) review, in which both authors and reviewers do know each other’s identities—a situation that might encourage ethical behavior among reviewers who cannot hide behind a cloak of anonymity. Studies of these two forms of review have, however, yielded mixed results. Logistics are an important hurdle: In trials of double-blind review, several medical journals found that about onequarter to one-half of reviewers were able to correctly guess authors’ identities despite blinding. And in trials of open review, referees who were asked to reveal their names to authors often refused to participate. There is nevertheless evidence that blinding does reduce bias. Joseph Ross of the Robert Wood Johnson Clinical Scholars Program led a five-year study, published in 2006, which showed that authors’ nationality and institutional affiliation affected acceptance of abstracts for the American Heart Association’s annual Scientific Sessions. Among thousands of abstracts submitted per year, blinded reviewers accepted about 12 percent fewer abstracts from prestigious institutions than did reviewers who were aware of authors’ affiliations. Blinded reviewers also accepted fewer abstracts from within the United States and more from outside the United States than did unblinded reviewers. Blinding must have reduced bias resulting from reviewers’
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assumptions about authors’ countries and institutions. Whether blinding also improves the quality of reviews is unclear. In 1990, Robert McNutt and colleagues found that blinded reviewers provided more accurate, well-supported and courteous reviews than did unblinded reviewers of articles submitted to the Journal of General Internal Medicine. But several years later, Amy Justice led a similar study with five different medical journals, and found no effect of blinding on review quality. Results for open review have been similarly mixed. One study at the British Journal of Psychiatry, led by Elizabeth Walsh, found that when referees revealed their identities to authors, they provided better reviews, were more courteous, took longer to complete reviews, and were more likely to recommend publication than were anonymous reviewers. But a pair of studies led by Susan Van Rooyen of the British Medical Journal found that revealing reviewers’ identities—either to authors or to co-reviewers—did not impact review quality or reviewers’ recommendations. The discrepancies among these studies of double-blind and open review could arise from their differing methodologies and sample populations. It is also worth mentioning that none of these studies examined the most serious ethical issues, such as respect for intellectual property. Future studies should take these factors into account, and they may eventually tip the balance in favor of one form of review or another. Conclusion
Peer review is a key feature of scientific publication, but it is susceptible to bias, inefficacy and other ethical transgressions. Alternative forms of review have produced only equivocal improvements in fairness and efficacy and have not been tested with respect to other problems. What are the next steps we should take to improve peer review? First, researchers should receive more education on how to review scientific articles—a skill that is not typically emphasized during research training. Some scientists do show students and postdocs how to review papers, and some research institutions cover peer review in seminars and workshops on research ethics. These practices must become more widespread. In particular, investigators should teach their trainees how to evaluate articles for scientific www.americanscientist.org
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merit and to follow ethical standards of peer review. Asking young scientists to help review papers is a good way to educate them, provided journal editors give their permission and the process remains confidential. Journals should also develop and publicize instructions for new reviewers and policies for reviewers and editors, just as they have done for authors. Rules should address confidentiality, fairness, conflict of interest, respect for intellectual property, and professionalism. Editors should carefully manage the peer review process to prevent or address problems and concerns. They should explicitly inform reviewers about their journals’ peer-review policies, remind reviewers to disclose conflicts of interest and return their reports on time, and delete any personal attacks from reviewers’ comments. If editors have evidence that a reviewer provided a poor review or abused the process, they should not invite that person to do other reviews. These ideals may be complicated when editors have difficulty finding experts willing to review a manuscript and when referees submit their reviews late, overlook errors, or disagree about the quality of a submission. Workshops and conferences on the subject could help editors to cope with these challenges. Finally, scholars should conduct additional research on the ethics of peer review. Our exploratory study of the experiences of NIEHS researchers suggests that some problems are common, but the results should be confirmed in other settings. Future work should determine how often ethical problems occur and how they affect scientists’ attitudes and behaviors. Studies should also address the causes of unethical behavior in journal peer review and the effectiveness of alternatives, such as double-blind or open review, at preventing various types of transgressions. There is certainly no perfect solution to the problem of quality control in the scientific record. Despite its flaws, the system adopted by the editors of Philosophical Transactions two and a half centuries ago seems to work as well as any method that has been tried—but its age and pervasiveness must not foster complacency. While journals, editors, and scholars work to understand and regulate peer review, it’s up to every individual scientist to maintain a thoughtful awareness of his or her participation in the process. Such vigilance
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and professionalism can only improve the quality of reviews, and might even spark new insights into how the review system could eventually be improved. Acknowledgments
I am grateful to Bruce Androphy, Zubin Master, Christine Flowers and Adil Shamoo for helpful comments. This essay does not represent the views of the NIH, the NIEHS or the U.S. government. Bibliography Committee on Publication Ethics. 2010. Code of Conduct. http://publicationethics.org/ files/u2/New_Code.pdf. Accessed Septem_______________ ber 4, 2010. Fisher, M., S. B. Friedman and B. Strauss. 1994. The effects of blinding on acceptance of research papers by peer review. Journal of the American Medical Association 272:143–46. Godlee, F., C. Gale and C. Martyn. Effect on the quality of peer review of blinding reviewers and asking them to sign their reports: A randomized controlled trial. Journal of the American Medical Association 280:237–40. International Committee of Medical Journal Editors. 2010. Uniform Requirements for Manuscripts Submitted to Biomedical Journals. http://www.icmje.org/urm_main. html. Accessed September 6, 2010. ___ Justice, A. C., et al. 1998. Does masking author identity improve peer review quality? A randomised controlled trial. Journal of the American Medical Association 280:240–242. Kravitz, R., et al. 2010. Editorial peer reviewers’ recommendations at a general medical journal: Are they reliable and do editors care? PLoS One 5:e10072. McNutt, R. A., et al. 1990. The effects of blinding on the quality of peer review: A randomized trial. Journal of the American Medical Association. 263:1371–76. Nylenna, M., P. Riis and Y. Karlsson. 1994. Multiple blinded reviews of the same two manuscripts: Effects of referee characteristics and publication language. Journal of the American Medical Association 272:149–51. Peters, D., and Ceci, S. 1982. Peer-review practices of psychological journals: the fate of published articles, submitted again. Behavioral and Brain Science 5:187–255. Resnik D. B., C. Gutierrez-Ford and S. Peddada. 2008. Perceptions of ethical problems with scientific journal peer review: An exploratory study. Science and Engineering Ethics 14:305–10. Ross, J. S. et al. 2006. Effect of blinded peer review on abstract acceptance. Journal of the American Medical Association 295:1675–80. Van Rooyen, S., et al. 1998. Effect of blinding and unmasking on the quality of peer review. Journal of the American Medical Association 280:234–237. Van Rooyen, S., et al. 1999. Effect of open peer review on quality of reviews and on reviewers’ recommendations: A randomised trial. British Medical Journal 317:23–27. Walsh, E., et al. 2000. Open peer review: A randomized controlled trial. The British Journal of Psychiatry 176: 47–5 2011 January–February
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Cracking Cellular Motion By applying biophysical principles to a simulated slice of a cell, researchers uncover molecular speed limits ment—more specifically diffusion— inside cells. When a molecule moves, the cellular fluid surrounding it gets disturbed. That affects the movement of other molecules, the pair concluded, just as one boat’s wake affects the motion of another craft traveling in the same lake. “It is exactly like a wake. If you start to move a solid through a liquid, you create a solvent flow. Imagine a very crowded day on Chesapeake Bay and all the sailboats are out. If you have ever been there you’ve seen that they interfere with one another. What’s remarkable is that these interactions persist almost to the molecular level,” says Skolnick, director of the Center for the Study of Systems Biology at Georgia Tech.
Dieter Wanke/Alamy
Three centuries after English scientist Robert Hooke first observed a cell with a microscope, multiple mysteries persist about life’s primary building blocks. It’s certain that cells are active places crowded with specialized biological components, including macromolecules. Those components communicate and otherwise interact to conduct the business of life. But we can’t yet explain, never mind mimic, precisely how it all works. Now two Georgia Institute of Technology researchers appear to have pushed the mission forward. Using advanced computer simulations, Jeffrey Skolnick and Tadashi Ando have identified hydrodynamic interactions as a key factor influencing move-
Using computer simulations, Georgia Institute of Technology researchers have identified hydrodynamic interactions as the most influential factor affecting how macromolecules move through the crowded cytoplasm of cells. Even though the scale is so much smaller, the effect is very similar to the way the wake from one boat affects another’s speed during an outing on a lake. 28
Skolnick and Ando, a postdoctoral scientist, reached this understanding after exploring a discrepancy. It has been long observed that macromolecules diffuse more slowly in native cytoplasm than they do in water, even though their viscosity is nearly the same. In at least one well-studied case, that of the molecular-laboratory workhorse green fluorescent protein (GFP), the rate in cytoplasm is ten times slower than the rate in water. The Georgia Tech scientists knew that proteins, nucleic acids and other macromolecules typically occupy 20 to 40 percent of cytoplasm volume. And they assumed that a physical principle played a role in the diffusion disparity there. “We deeply believe that the principles of physics should work for biology,” Skolnick says. But they didn’t know what principle counted most. So they developed a simplified computer model of an E. coli cytoplasm populated by 15 different macromolecule types. Then, based on measurements of the molecules’ physical properties detailed in the scientific literature, they calculated the likely effects of multiple natural forces on those macromolecules. That included estimates of attraction and repulsion between molecules, the effect of their different shapes, and their hydrodynamic interactions. Crowding alone drops the diffusion constant of GFP by a factor of three. Then, by far, the influence of hydrodynamics—which produced size-independent intermolecular effects—was the biggest. When it was considered too, the green fluorescent protein’s diffusion constant matched the rate in vivo. The pair’s observation, published in October in the Proceedings of the National Academy of Sciences of the U.S.A., will be useful to other scientists trying to build dependable predictions of how proteins in cells interact, says David Thirumalai, director of the Biophysics Program in the Institute for Physical Science and Technology at the University of Maryland. Before anyone can
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For Skolnick and Thirumalai, findings such as these also contribute to a much larger goal: the drive to more realistically simulate whole cells with computers, or “in silico.” Multiple laboratories worldwide are chasing that very thing. Skolnick for years has sought ways to predict the structure of biologically active forms of proteins. Thirumalai is hunting for general principles that govern the folding of biomolecules. Biologists have made huge strides in recent decades in producing “the parts list” of molecular life, Skolnick says. The challenge now is to accu-
Get a Grainy Grip Robot hands may work better if they look more like beanbags than fingers
Often robots require some sort of grasping apparatus in order to interact with the world. But simulating a hand is an incredibly difficult engineering task. The device must apply the correct amount of force—enough to hold on to and object, but not so much that it crushes it. An impressive array of grippers has been developed, but physicist Eric Brown and his colleagues at the University of Chicago, Cornell University and iRobot Corporation think one form might be both simpler and more versatile than many others: the sandbag. “Most robots nowadays are metal, wheels, gears, batteries and claws—all hard components. People and animals are made of soft materials and we can do a lot of things that robots aren’t good at yet. So maybe we should start building soft robots,” says Brown. “Our expertise here is in the jamming of granular materials. Materials like sand can flow kind of like a liquid, but if you compact them tightly, they can be very hard and solid, like a vacuum-packed bag of coffee. We came up with gripping as a place where we could apply the physics of this transition from liquid to solid.” Foregoing the idea of even trying to look like fingers, the team made a grip-
per that consists of a balloon filled with granules (in one prototype, they actually used ground coffee) that conform to the shape of a wide range of objects. As the group reports in the November 2 issue of the Proceedings of the National
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estimate the timing of those interactions, it’s vital to know how quickly cells’ components can move, he says. “Jeff and [Tadashi] have shown that to compute this stuff, you must take into account the effects of the hydrodynamic interactions. This has been known to people doing fluid dynamics for a long time. In the context of cellular biology, this helps set time scales for biological processes,” Thirumalai says. “One must know how to compute the diffusion constants to make the next step and predict how quickly some reactions will take place.”
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rately place those parts into a dynamic view of the components interacting with one another. Once that’s done, Skolnick says, researchers can ask lots of new questions, knowing, of course, that they are working with caricatures of real cells. Still, better understanding may be coming of the mechanics of evolution, he says, or just how normal cells transform into cancer cells, among many other things. “You have the possibility of looking at a lot of life,” Skolnick says. —Catherine Clabby
Academy of Sciences of the U.S.A., a vacuum tube is used to suck the air out of the membrane, compacting the granules and making the gripper rigid in shape around the object. The object can be lifted and moved, then the vacuum turned off in order to release it. In tests with a gripper of about 4 centimeters in diameter, Brown and his colleagues were able to successfully pick up and move objects with shapes as varied as spheres, cubes, springs, jacks, foam ear plugs and screwdrivers. The gripper could pick up light bulbs and
A novel robotic gripper, basically made of a balloon filled with coffee grounds that are compacted with a vacuum, can draw, pour, delicately lift a raw egg or haul heavy objects such as a shock absorber. (Photos by John Amend of Cornell University.) www.americanscientist.org
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raw eggs without damaging them, lift a glass and pour water from it, or grasp a pen and draw. The device did have trouble picking up extremely thin disks or very soft objects such as cotton balls. Applying a vacuum to reduce the volume of the grains by as little as 0.5 percent was enough to jam them together. “You don’t have to close your fingers with a precise amount of strength to hold a wine glass; there’s a lot of tolerance there,” Brown explains. “Because our gripper is soft, I can use one pressure to pick up a lot of different things without breaking them.” The team has calculated that the gripper could theoretically be scaled up to a meter in width and be capable of lift-
ing weights up to 10,000 kilograms. The idea of using soft fingers on robot grippers has been around for some time. However, until recently the mechanism of jamming grains was not sufficiently understood. “The part of our gripper that was really new was using the jamming transition as a way of pinching and holding onto things— the idea that you don’t actually need claws, or muscles to close your fingers around something, that we could use only the soft, granular material with just some confining pressure to do that work for us,” Brown says. The team is exploring the idea of creating jamming-based pads on the fingers of existing robot grippers in order
Unauthorized Reproduction Not Prohibited Fatherless boa litters extend the realm of parthenogenic vertebrates Evolution went to a great deal of trouble to conjure up the apparatus of sexual reproduction in animals: chromosome-sorting machinery in the cell, organs of intromission and oviposition, crests and trumpets and scent and pretty fans to get attention. In theory it’s all worth it, paying the dividend of constantly refreshed genetic diversity. Yet here and there in the animal kingdom, organisms withdraw from the mating derby. Parthenogenesis is
One of 22 siblings, all fatherless, from two boa litters by the same mother. (Image courtesy of Warren Booth.) 30
the production of offspring without fertilization by a male. It seems a plausible enough lifestyle choice for the tiny and squiggly—say, rotifers, aphids and nematode worms. The idea takes a bit more getting used to for larger animals such as some lizards and a few birds, but anyone who studies biology learns to be unsurprised by the exotic tendrils that form in evolutionary space. So long as things don’t get out of hand. “I have literally gotten no work done this week because of answering phone calls and emails,” says Warren Booth of North Carolina State University, who recently reported the first scientifically confirmed case of parthenogenesis in a boa constrictor in Biology Letters. The unusual litter came to his attention through a network of boa enthusiasts, one of whom had a female with two litters exhibiting anomalous recessive coloration. Booth agreed to apply a microsatellite DNA fingerprinting test he’d developed for another study to see if something strange had occurred. “I thought it was going to be stored sperm or local males,” Booth explained. “I said, ‘Send me the shed skin.’” Earlier examinations of parthenogenesis had relied mainly on behavioral and perhaps surgical analyses.
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to expand their versatility. They also think their gripper would be good for search-and-rescue uses, where it could quickly sort through rubble piles, or for landmine removal. And they are working on creating more robust containment membranes for the gripper that won’t degrade from hard use. In fact, the device may so effectively emulate the functionality of the human hand that it might help those who have lost one. “Another application we’ve been talking a lot about is prosthetics, because the control is very simple; you wouldn’t need a lot of remaining muscle control to operate the hand itself,” Brown says. “It could be a simple pushbutton control.”—Fenella Saunders
Using DNA fingerprinting, Booth demonstrated with an infinitesimal margin of error that the offspring were, allele by allele, including that rare color trait, genetic matches of the mother. Oddly enough, Booth’s colleague at N.C. State and coauthor of the Biology Letters paper, Edward Vargo, reported a similar discovery in 2009 in Science, showing that subterranean termites produce queen successors by parthenogenesis. (Neither researcher had a special professional interest in the topic beforehand.) Odder still, Booth was a Ph.D. student in the lab of Paulo Prodöhl when Prodöhl was coauthor of a 2008 paper with Demian Chapman reporting parthenogenesis in—most unexpectedly—hammerhead sharks. “It’s kind of like parthenogenesis has been following me,” says Booth. With his latest report, stalking might be the better word. He pulls open a file drawer of newly arrived correspondence and shed skins from around the world. The true prevalence of parthenogenesis has been something of a mystery. Suspected cases are flowing into Booth’s inbox. We now have the molecular tools to rapidly address relatedness in populations and individuals, and unequivocally settle paternity cases in the wild. With attention turned to parthenogenesis, will we finally see the first example in mammals? Highly unlikely. Early mammalian development has a strict requirement for genetic contributions from a male and a female parent; noncompliance dooms the embryo. Mammals are most likely committed to propagating the old-fashioned way.—Morgan Ryan
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In the News This roundup summarizes some notable recent items about scientific research, selected from news reports compiled in Sigma Xi’s free electronic newsletters Science in the News Daily and Science in the News Weekly. Online: http://sitn.sigmaxi. org __ and http://www.americanscientist.org/sitnweekly
Time Flies East to West For natives of northeast Australia, time advances westward. Although many cultures use cardinal directions to denote the locations of objects, linguists have so far found only one—the aboriginal community of Pormpuraaw— that assigns an absolute vector to time. Researchers asked 14 Pormpuraawans and 14 Americans to perform tasks such as arranging pictures in chronological order. The Americans organized times from left to right, but Pormpuraawans overwhelmingly arranged them east to west—regardless of which way they were facing. The Pormpuraawans’ system may be an abstraction of the daily east-west path of the sun. Boroditsky, L., and A. Gaby. Remembrances of times east: Absolute spatial representations of time in an Australian aboriginal community. Psychological Science (published online October 19)
Scared Nitrogenless Grasshoppers are afraid of spiders. That anxiety boosts their metabolism by up to 40 percent, shifts their diet, and could alter grassland ecosystems. In both terrariums and field enclosures, grasshoppers (Melanoplus femurrubrum) that felt threatened by spiders (Pisaurina) chose food with more carbohydrate fuel relative to nitrogen. The insects’ bodies and feces therefore became nitrogen-deprived, www.americanscientist.org
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and their selective grazing favored the growth of nitrogenpoor plants. All that translates to less-nourishing meals for predators and inferior fertilizer for the soil. The authors suspect that the cascading effects of herbivore fear could affect ecosystem productivity and food-chain length. Hawlena, D., and O. J. Schmitz. Herbivore physiological response to predation risk and implications for ecosystem nutrient dynamics. Proceedings of the National Academy of Sciences 107:15503–15507 (August 31)
A Robotic Ruse Engineers have programmed robots to strategically deceive, an ability they say might be useful on the battlefield. The researchers created a new series of algorithms that tell a robot when it’s appropriate to lie (when it’s in a conflict and stands to gain by dishonesty) and how to use knowledge of its adversary to deceive effectively. In a real game of robot hide-and-seek, one machine learned to dupe its seeker by toppling markers en route to a false hiding place. The trick worked in 15 out of 20 trials, but there’s still a lot of work to do before robots can (or should) go on to mislead cleverer opponents. Wagner, A. R., and R. C. Arkin. Acting deceptively: Providing robots with the capacity for deception. International Journal of Social Robotics (published online September 3)
The Repurposed Cortex Congenitally deaf cats have keen sight, with a heightened ability to detect movement and peripheral objects. To find the brain regions responsible for deaf cats’ enhanced vision, neuroscientists reversibly shut down individual brain areas by chilling them.
The key regions were parts of the auditory cortex that normally detect the movement and location of sound—but that, in deaf cats, process visual stimuli instead. Brain regions that perform general tasks, such as detecting movement, may be more amenable to revamping than are regions that perform sense-specific skills, such as discerning color or tone. Lomber, S. G., et al. Cross-modal plasticity in specific auditory cortices underlies visual compensations in the deaf. Nature Neuroscience 13:1421–1427 (November)
cropland. That’s according to a new analysis of data from more than 800 weather stations in the northern mid latitudes since 1979. Nearly three-quarters of those sites saw a 5 to 15 percent decline in annual average wind speed 30 feet above the ground, confirming a trend previously observed in smaller local datasets. Increased vegetation—mostly as a result of post-Soviet land-use changes in Eurasia—accounted for a large share of the calming. Whether climate change may also have a role is unclear, but climatologists will be watching closely for continued shifts in the wind.
Largest Marine Virus Giant viruses straddle the boundary between living and nonliving. For example, the recently sequenced Cafeteria roenbergensis virus (CroV) boasts a 730,000-base-pair genome. That’s the largest yet found in a marine virus, and bigger than some bacterial genomes. CroV still can’t reproduce without its host (the single-celled predator C. roenbergensis), but it does encode most of the proteins it needs for replication. That sets it apart from better-known viruses that carry only a handful of genes. Microbiologists are still trying to understand how giant viruses got so big; CroV seems to have duplicated many genes and also acquired some from other organisms. Fischera, M. G., et al. Giant virus with a remarkable complement of genes infects marine zooplankton. Proceedings of the National Academy of Sciences (published online October 25)
Dying Winds The Northern Hemisphere is calmer than it was 30 years ago, in part because forests are reclaiming abandoned
Vautard, R., et al. Northern Hemisphere atmospheric stilling partly attributed to an increase in surface roughness. Nature Geoscience (published online October 17)
Heads Up! If only birds would watch where they’re flying, power lines might not be such a menace. But for species with an expansive blind spot, that’s not so easy. Working with a handful of fowl from South African zoos, researchers performed eye exams on species that suffer high mortality from power-line collisions. They discovered a large blind spot in kori bustards (Ardeotis kori) and blue cranes (Anthropoides paradisea). When these species look down to spot roosts or other birds while flying, their blind spot is dead ahead, obscuring dangerous wires. Distracting such birds away from power lines—rather than adding flags and reflectors to the wires themselves—may be a good conservation strategy. Martin, G., and J. Shaw. Bird collisions with power lines: Failing to see the way ahead? Biological Conservation 143:2695–2702 (November) 2011 January–February
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Fractures and Bindings of Consciousness Observing how awareness breaks down in epileptic seizures provides clues to its normal workings in the brain
Don M. Tucker and Mark D. Holmes
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very second, our brains take feedback from the world and provide us with a sense of consciousness: awareness of what we are doing and what we have just done. How this process works in the brain is no simple matter. But sometimes examining how a process fails—as consciousness does in people afflicted with epilepsy—enlightens us to how it works. With recent advances in mapping the spread of epileptic seizures, we can now align the unique fractures in consciousness that occur during seizures with the interference that seizures cause in specific cerebral networks. Loss of ongoing memory, which disrupts the continuity of consciousness, occurs when seizures spread through the brain’s corticolimbic networks. The fractures in consciousness that occur in these limbic seizures suggest that one component of consciousness is provided by ongoing memory, which allows us to use the knowledge of the immediate past and anticipate the immediate future. This component of consciousness is necessary for the mind’s continuity in time. Volitional control of consciousness is disrupted in absence spells, in which a seizure spreads through frontothalamic circuits. The disruption of mental capacDon M. Tucker is CEO and Chief Scientist of Electrical Geodesics, Inc., a manufacturer of densearray electroencephalography systems. He is also a professor of psychology and associate director of the NeuroInformatics Center at the University of Oregon. His research examines neural mechanisms of human emotion and cognition. Mark D. Holmes is a professor of neurology at the University of Washington. He is an attending physician at the University of Washington Regional Epilepsy Center and is the director of the EEG and Clinical Neurophysiology Laboratory at Harborview Medical Center in Seattle. His research explores new advances in the diagnosis and treatment of refractory epilepsy. Address for Tucker: Electrical Geodesics, Inc., 1600 Millrace Drive, Suite 307, University Research Park, Eugene, OR 97403. E-mail: ________
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ity in absence spells suggests that an integral component of consciousness is the voluntary control of intentions. This component is closely related to, but separable from, selective attention, in which some contents of consciousness are “spotlighted” while others fade to the background. The control of intentionality allows consciousness to coordinate mental resources and to provide the sense of one’s active role in personal experiences. Finding Consciousness A classic debate in brain research has been that between localization and mass action. The question is whether psychological functions, such as spatial memory and verbal reasoning, are localized in specific brain regions, or whether they emerge from the mass action of the brain as a whole. With modern evidence on localized brain activity, as seen by neuroimaging methods such as functional magnetic resonance imaging (fMRI) or dense-array electroencephalography (dEEG), it may seem that localization clearly has won out. Indeed, localized brain activity can be reliably demonstrated with many cognitive tasks. However, the best scientific understanding we have of how psychological function could arise from human neural networks has come from artificial neuralnetwork models in computational neuroscience. These models illustrate principles of distributed-information representation that are very similar to the classical notion of mass action. A primary principle, sometimes called connectionism, is that information is represented in the patterns of connections between neurons, not in the neurons themselves. Connectionist simulations show brainlike properties that have never been possible to create with traditional artificial intelligence. One example is content-addressable memory. With a conventional comput-
er, you must specify not only what is to be stored in memory but the “address” where it is to be placed. But when information is represented in the patterns of connections in a network, then simply presenting the network with the content (such as the pattern of a face to be recognized) causes it to address that memory as an intrinsic feature of the activation of the widespread distributed connections. Informed by principles of distributed computation, neuropsychological theorists have generated new concepts for relating complex qualities of the human mind to the specific properties of cerebral networks. For example, Giulio Tononi at the University of Wisconsin and Christoph Koch at the California Institute of Technology have drawn upon connectionist reasoning as they interpret evidence suggesting how consciousness might arise within the large-scale networks of the cerebral hemispheres. Although the study of anatomy shows that there are extensive neural connections within and between the cerebral hemispheres that could be active, Tononi and Koch theorize that consciousness emerges from the dynamic pattern of physiological connections that are active at any one point in time as an integrated assembly. The idea of memories stored in the patterns of connections among neurons was first formulated by Sigmund Freud in the 1890s. The issue was addressed by mathematical formulations of nervenet cybernetics by Warren McCulloch and Walter Pitts at the University of Chicago in the 1940s. This issue remains important to modern neuroscience theories such as that proposed by Tononi and Koch. From the connectionist perspective, if we could understand the control of large-scale physiological assemblies in the brain, we could also understand the control systems necessary for regulating consciousness.
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“. . . I have had in all four great crises, during which I didn’t in the least know what I said, what I wanted and what I did. Not taking into account that I had previously KDGWKUHHIDLQWLQJ¿WVZLWKRXWDQ\SODXVLEOHUHDVRQ´ letter from Vincent van Gogh to Wilhelmina van Gogh, April 30 1889 Figure 1. The letters of Vincent Van Gogh provide evidence that he could have suffered from seizures. Whether he or numerous other historical figures had epilepsy remains a matter of debate, but the disease is estimated to affect 1 percent of the world’s population. New dense-array electroencephalography (dEEG) devices take much of the guesswork out of determining when seizures occur, and can also localize their activity to specific brain regions. Such data may help neuroscientists determine what regions of the brain are key in maintaining consciousness.
All of this information leads back to epilepsy, because a dramatic clue to the sensitization and spread of physiological network assemblies may be found in the pathological phenomena of seizures. The ways that seizures engage certain networks and not others may show how www.americanscientist.org
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dynamic ensembles of neurons can be formed within specific anatomical networks. The psychological deficits that are characteristic of these specific seizures may then provide clues to the normal separation of the functional components of consciousness.
A Nested Framework A first principle of neuropsychological function is basic enough that it is easily overlooked. The human brain’s psychological operations are organized in relation to its general architecture, which comprises a nested hierarchy of 2011 January–February
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cerebral cortex (telencephalon)
thalamus and hypothalamus (diencephalon)
mesencephalon diencephalon telencephalon
midbrain (mesencephalon)
Figure 2. The vertical organization of the brain is best seen in the fetal stage (left) before the extensive folding of the cortex. The major divisions of the brain emerge during development in an order that traces the major stages of vertebrate neural evolution. A side view of an adult human brain’s right hemisphere (right) shows the limbic regions at the inner core, and the brain stem with the thalamus and hypothalamus at its top. All levels of the brain still remain dependent on their evolutionary progenitors for critical support and control functions.
the evolved structures of the vertebrate brain. This hierarchy can be described as a vertical dimension of neural organization: More recently evolved structures are stacked on top of more primitive ones (see Figure 2). As seen most clearly in the still-forming brain of the human fetus, the cortex is dependent on the major circuitry of the subcortical telencephalon, including the limbic circuits and those of the basal ganglia. These telencephalic (end brain) systems are in turn dependent on regulatory influences from the thalamic and hypothalamic divisions of the diencephalon (interbrain), which sits on top of the brain stem and provides a gate for the traffic into and out of the telencephalon. The functions of the diencephalon are in turn dependent on ongoing support from the brain stem’s mesencephalic, metencephalic and myelencephalic levels of organization, regulating primitive but essential functions such as breathing, heartbeat and the brain’s level of arousal. Figure 3. Temporal-lobe seizures (right) may originate from the hippocampus or the lateral temporal cortex (inset, red). Seizures are often heralded by an aura, followed by loss of consciousness or a dreamy state. Attacks last a minute or two, but disorientation can continue for hours, and memory loss can occur. Absence seizures (left), which tend to affect children, may originate in the frontal lobe (inset), may occur dozens of times a day, and begin and end abruptly. Once the attack ends, patients resume activity as if it had never happened. 34
Some people with epilepsy experience generalized tonic-clonic seizures, or convulsions. Convulsions are the most severe form of an epileptic seizure and tend to “generalize” or spread throughout the brain’s vertical organization. As they do, these seizures provide a clear demonstration of the brain’s vertically
absence seizure
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organized architecture, through which more recently evolved networks are embedded within the control mechanisms of more primitive networks. To the extent that multiple vertical levels of the brain’s control systems are involved in major changes in consciousness, such as in sleep and dreams, we can see that these nested control systems of the brain must be continually integrated to shape qualities of everyday experience. More specific clues are given by seizures that remain limited to specific circuits in the forebrain (the diencephalon and telencephalon). Seizures that do not spread are described as localizationrelated or partial seizures. If they impair consciousness, they are termed complex partial seizures. A common feature of these seizures is that they engage the limbic networks at the medial core of the cerebral hemisphere. The limbic networks are centered on the medial temporal lobe, so when epilepsy involves partial seizures, it is often referred to as temporal-lobe epilepsy. It is the most common form of epilepsy in adults. In patients with recurring temporal-lobe seizures that are poorly controlled by antiepileptic drugs, neurosurgical removal of the epileptic tissue may be necessary. In that case, localizing the onset
temporal-lobe seizure
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Figure 4. Recording the brain’s activity at all points on the head surface requires a dense array of electrodes (256 in the device shown in a). Multiple images of the head and the sensors are taken simultaneously from different angles (b, top right), the sensors are identified in each image with computer vision (b, bottom), and a three-dimensional point cloud of sensor positions is generated (b, top middle). The sensor points provide accurate registration of the electrical data with the brain and head. (Images are courtesy of the authors, unless otherwise indicated.)
of the seizure discharge is necessary to guide the neurosurgical procedure. It is critical to determine that the patient’s seizures stem from one temporal lobe, and only that temporal lobe, if the limbic tissue of that lobe is to be removed. With recent advances in dEEG technology, sampling the brain’s electrical field can be accomplished with electrodes that cover the head fully. With adequate coverage, the electrical measurements can then be registered with a three-dimensional MRI of the person’s head tissues. Then computer visualization can extract the cortical surface and build a detailed electrical model of the person’s brain. With this precise electrical model and dense-array measurement, the onset of seizure activity can be estimated from the noninvasive dEEG at the head surface. Validation studies with intracranial electrodes, placed directly on the brain surface, have provided evidence that the dEEG estimate of seizure onset is sufficiently accurate to guide neurosurgery. Limbic Central Clinically, epileptologists and neurosurgeons have considerable evidence showing that when seizures appear to begin in the temporal lobe, they are starting in the limbic networks of the medial temporal lobe. To understand why limbic networks tend to generate seizures, researchers have conducted experimental studies of induced seiwww.americanscientist.org
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zures in animals. This research has suggested that the reactivity of limbic networks in epilepsy reflects the high level of electrophysiological, and perhaps functional, excitability of limbic tissue. The limbic networks are in a good position to be reactive to events anywhere in the hemisphere because they are centrally located. The last several decades of neuroscience research have yielded important insights into the connectional architecture of the cerebral hemispheres, and a key finding has been the central role of limbic networks. Research by Deepak Pandya and his colleagues at Boston University has introduced quantitative methods to studying the connectivity of the primate cortex. In the earlier qualitative studies, any neural connection between one area of cortex and another was sufficient to consider them connected, leading to complex, rather indiscriminate maps that implied that most areas of cortex were interconnected to each other. Instead, the quantitative studies showed that the primary paths of neural connections link the sensory and motor cortices with their bases in limbic cortex. Moreover, the density of interregional connections (for example, connecting auditory with visual association areas) becomes greater closer to the limbic system. The implication of this connectional anatomy is that the limbic regions are the primary integrative networks of the hemisphere, whether for
sensory integration in the posterior brain or for motor organization in the anterior brain. The architecture implied by this evidence is remarkable. It shows how the classic “association” areas of the cortex are actually intermediate, falling between primary sensory or motor areas and their limbic base. This architecture can also help explain why seizures tend to engage limbic regions: These regions are at the core of the hemisphere’s connectivity. The functional significance of the hemisphere’s connectional architecture is clearly illustrated by the role of corticolimbic interaction in forming memories. This activity results from the interaction between the neocortical networks, for example, those handling sensory or motor functions, and the limbic networks at the core of the hemisphere. Evidence from both human clinical studies and animal experiments has shown that if the connections between neocortex (for example, auditory cortex) and limbic cortex are severed, the relevant memories (for example, memories of sounds) cannot be formed. Previous memories may be recalled (depending on the severity of the brain lesion), but new ones cannot be created. This evidence has two important implications. First, memories are not localized in one spot in the hemisphere but are distributed across multiple networks, including limbic, association cortex and primary (for example, auditory) cortex. Second, in order to 2011 January–February
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b reconstruction of the cortical surface from the segmented volume
a segmentation of cortex gray matter and white matter from brain image
c tessellation of the cortical surface into 2,400 patches (1 square centimeter each)
Figure 5. Localizing electrical brain activity requires segmenting the tissue of the head to identify the cortex (left), extracting the cortical surface with computer vision technology (top right) and then creating a model of the cortex where each patch is an electrical dipole (bottom right).
form a memory, some physiological process, often called consolidation, is necessary to allow the perception of an event to engage responses in limbic cortex. These responses then feed back (in some way not yet understood) to energize the memory trace, which is not discretely localized but, rather, distributed across the linked corticolimbic networks. Binding of Ongoing Memory The limbic networks, linked closely to the body’s homeostatic, visceral regulatory mechanisms in the hypothalamus, are responsible for motivational control. Considering this, a reasonable hypothesis is that the functional role of limbic networks in memory consolidation is to regulate the memory process to ensure that motivationally significant experiences are provided with adequate consolidation to be retained in memory. Remarkably, the same excitability of limbic circuits that causes them to resonate to motivationally significant experiences may lead them to be seizure-prone. We have seen that human epilepsy often involves the temporal-limbic networks; some researchers have hypothesized that the recurrent seizures of 36
epilepsy may progress toward temporal involvement wherever they originate in the cortex. In a phenomenon called kindling, seizure discharges in experimental animals are first started in an area of neocortex through repetitive electrical stimulation. The first stimulation causes only a direct local discharge, but subsequent stimulations cause a kindling or exaggeration of the response, leading to continuing, seizurelike discharges. The researchers using this method soon found that wherever the kindling was started, the seizure discharges tended to progress to the limbic core of the hemisphere. The close association between kindling and learning was discovered in an experiment a number of years ago by the team of Jerri Janowsky at Oregon Health Sciences University. The team found that seizures, once kindled in an animal’s brain, could be conditioned or learned through association with a sensory stimulus, such as a sound. The limbic resonance that recruits the electrophysiological excitement of a seizure appears similar if not identical to that which recruits the consolidation of a significant event in memory. If limbic seizures impinge on the anatomy of memory, what happens to a per-
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son’s memory after a seizure? Typically, the person shows retrograde amnesia, meaning the loss of memory extends gradually back in time for minutes or even hours before the seizure. Because of this recent memory loss, the person is disoriented and unable to act coherently. The person has no ongoing memory of his or her location or what has been happening. This is a clue to the normal coherence of consciousness in time. Given the critical role of temporal and limbic networks in memory, seizures that affect these networks most strongly may be expected to cause severe impairment of recent memory. Observations by Dan Drane of the University of Washington’s Regional Epilepsy Center have suggested that temporal-lobe seizures may indeed affect recent memory more than other seizure types. We think that the disorder of recent memory that accompanies limbic seizures provides an important clue to the neurophysiology of a key aspect of consciousness: ongoing memory. Without the continuity of recent memory, and the associated ability to anticipate the immediate future, the temporal span of consciousness becomes vanishingly thin. Imagine that you have no memory of what happened one second ago. Are you still conscious? Certainly you are conscious of this one second, and you could argue that immediate consciousness is preserved. Yet even a moment’s reflection makes it clear that there must be some historical scope of awareness—and without it, functional consciousness retracts toward a complete loss of meaning. Recognizing that limbic memory mechanisms are the basis of the frontal lobe’s ability to plan for future actions, the late Swedish neuroscientist David Ingvar described planning as “memories of the future.” Similarly, acknowledging the limbic base of the cerebral hemisphere’s functional architecture, American biologist Gerard Edelman described consciousness as “the remembered present.” Considering how normal consciousness requires both the context of recent memory and the projection of events into the unfolding future, we suggest that ongoing memory is an essential component of human consciousness. As shown by various disorders of consciousness, including not only limbic seizures but delirium and dementia, the loss of ongoing memory is devastating for the conscious control of cognition. As recent memory shrinks, so does conscious anticipation of the fu-
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ture. Ongoing memory allows us to orient to person, place and time. In normal consciousness, we continually project the active residuals of immediate history into the unfolding future, thereby maintaining the temporal continuity of mind. Careful analysis of the effects of limbic seizures thus provides a novel insight into neuropsychological activity that binds the mechanisms of consciousness in time. This insight can be refined further by contrasting limbic seizures with a disorder of consciousness caused by a kind of seizure that specifically does not impair ongoing memory. Absence Spells Although they may continue into adulthood, absence seizures typically affect children. There is a momentary disruption of consciousness, during which the person is unresponsive and unable to carry out voluntary actions. However, unlike the loss of consciousness from any other neural disruption—such as fainting, drug toxicity or concussion— the person does not fall down, appears to be alert and does not become disoriented. During the seizure, the brain emits large spike-wave discharges that Figure 7. A complex nervous circuit links the frontal cortex to the thalamus. The thalamic projections to the cortex are regulated by the thalamic reticular nucleus, which is itself regulated by the frontal cortex. www.americanscientist.org
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suggest a generalized seizure. However, immediately after this typically brief seizure, the person may continue the previous activity or pick up the conversation where it left off, showing that he or she remains fully oriented in time. The absence spell is thus a remarkably specific lesion, or disruption, of consciousness, and it is particularly remarkable in what it does not cause: disruption of ongoing memory. Consistent with this specific psychological effect, the anatomy of absence epilepsy provides clues to a specific circuitry of the thalamus and frontal lobe. The implication is that this neural circuitry must
Figure 6. To validate the accuracy of dEEG localization, the authors compared its results to a direct recording of seizure onset made by a grid of electrodes surgically placed on the cortical surface (b). Simultaneous readings from the intracranial electrodes (a, left) and dEEG (a, right) were taken continuously for several days. Thick lines in the tracings indicate seizure onset; dEEG accurately showed onset location (red dots) and seizure spread (blue and then green dots, chronologically) for these episodes, which allowed for a successful surgical treatment.
be integral to the voluntary control of thought and action in the normal brain. Several lines of evidence suggest that abnormal discharges from the thalamus figure in the development of spike-wave seizures in animals, and in similar discharges in absence epilepsy. The thalamus can be described as the gateway to the cerebral cortex, binding the networks for specific mental functions. With the exception of the sense of smell, all sensory and motor pathways enter or exit the cortex through thalamic relays, and the thalamus is capable of blocking transmission in these relays. A unique feature of the thalamus,
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the thalamic reticular nucleus (TRN), is a thin sheet of neurons surrounding most of the thalamus. This network provides direct inhibitory control over the thalamocortical relays. Importantly, as another example of the complexity of the brain’s self-regulatory systems, the TRN is itself under cortical control, from specific networks in orbital and frontopolar cortex. This evidence of a localized, frontallobe control network for regulating thalamic mechanisms has proven important in interpreting localized seizure activity in absence spells. In our dEEG studies of the pathological discharges during these spells, we found that, even though these discharges were thought to cover large areas, the spikes are highly localized. Indeed, they are specifically localized to the orbital and frontopolar networks of the frontal lobe, which are in turn critical to regulating the thalamus. The implication of this new evidence is that the seizure discharge reflects some abnormality in the physiological activity in the frontal networks that then cascades in a pathological loop through the frontothalamic circuitry. The cortical discharge appears to affect the TRN and thalamus, and thereby disrupts the thalamic control of the cortex itself, perhaps leading to the next cascade of spike-wave discharge. Does this evidence of pathological function provide clues to the normal, adaptive functions of the frontothalamic circuitry? The evidence is complex, because it suggests even greater specificity in separating the circuits controlling attention (the application of mental resources to certain events or topics) from intention (the current goal of mental activity). Patterning the Spotlight The specificity of the frontal lobe’s control over thalamocortical mechanisms of attention has been demonstrated by recent anatomical evidence gathered by Basilis Zikopoulos and Helen Barbas at Boston University. These data show how specific networks in the frontal lobe project to specific regions of the TRN, and thereby to specific thalamic nuclei. The relevance to controlling attention is shown by the pathways from certain Figure 8. Each interval of a spike-wave seizure (graph, top) is localized with dEEG onto a colored map (red is positive electrical potential, blue is negative) of the head surface (bottom, left). MRI images from each time point show localized electrical activity as bright spots (bottom, right).
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frontal networks (on the lateral surface) that project to the regions of the TRN that control the specific sensory nuclei of the thalamus. These circuits are well suited to controlling the “spotlight” of attention by allowing the thalamus to highlight certain sensory data while pushing other input to the background. Importantly, however, the seizure discharges during an absence spell do not seem to engage the frontal networks that regulate the spotlight of attention. Rather, in our dEEG studies we found that the spikes of spike-wave absence discharges engage the medial frontal poles; these are the networks that Zikopolous and Barbas found to be connected to the rostral pole of the TRN, which in turn projects to the anterior nuclei of the thalamus, also called the limbic thalamus. This frontothalamic circuit, rather than controlling the spotlight, appears to integrate limbic contributions to the state of arousal and motivation. One interesting line of animal research suggests that activity in this circuit is related to the animal’s head orientation, apparently tracking the self-centered locus of the animal’s current intentions. Considering this specific functional circuitry in the seizures that cause absence spells, we think that the loss of conscious control of behavior in this disorder reflects an impairment of a frontothalamic circuit that is integral to the voluntary control of intention. This is not the selective attention to one sensory focus, but the maintenance of the alert intentional state that allows cognition and behavior to pursue a motivated goal. Absence seizures thus disrupt a specific component of consciousness, the person’s current intention that then binds multiple other component mental operations within a coherent, goal-oriented episode of experience. Even as voluntary intention is disrupted in the absence spell, ongoing memory remains relatively intact. This implies a fractionation of consciousness by different seizure types. Limbic seizures impair ongoing memory over a considerable interval of time, so that even as consciousness is regained it is incomplete and disoriented. Absence seizures create a more focal disruption of consciousness, impairing voluntary intentional action but not degrading the continuity of ongoing memory. With ongoing memory more or less intact, the person retains the subjective orientation to the immediate experiential context, and can therefore pick up the conversation where it left www.americanscientist.org
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off. By fractionating consciousness in a specific way, absence seizures show the specificity of both what is lost (voluntary intention) and what is retained (ongoing memory and orientation). Dynamic Consciousness The unique fractures in consciousness that occur in seizure disorders may offer clues to the underlying mechanisms that bind consciousness within the large-scale networks of the cortex. Ongoing awareness of the context appears to require the operation of corticolimbic networks. Interestingly, this contextual awareness is needed to meet the clinical test of mental competence. To provide a quick assessment of impaired consciousness when a patient appears confused, physicians and psychologists use the test of “orientation times three.” This tests orientation to person (“What is your name?”), place (“Can you tell me where you are?”) and time (“What is the date today?” “What month is it?” “Do you know who the U.S. President is now?”). Consciousness may be clouded temporarily by delirium or disorganized permanently by dementia. In contrast, volitional control of consciousness seems to require frontothalamic circuits, both for the selection of focused processing, such as in selective attention, and for the regulation of the more general state of purposeful intention, which is impaired during the absence spell. Thus both corticolimbic and frontothalamic mechanisms appear necessary for normal consciousness. They seem to bind patterns of physiological coherence within cerebral networks. And certainly this is only part of the story of the brain’s physiological assemblies: These patterns of network coherence must be organized within the general pattern of vertical integration, drawing on support from brain stem projection systems that regulate cerebral arousal. Consciousness as a Phenomenon It probably makes sense to most people to consider consciousness as a unitary phenomenon, an indivisible quality of subjectivity. Yet the fracturing of consciousness in absence seizures is particularly impressive evidence for the hypothesis that some aspects of explicit voluntary control, mediated by frontothalamic circuits, can be separated from the continuity of ongoing memory. When we employ reasoning from anatomy and the specificity of absence discharges, even
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finer distinctions can be made, implying that the selection of the focus or spotlight of attention is separable from the voluntary control of the intentional state itself. Now that we can separate them through neurophysiological analysis, can we recognize these components of consciousness in subjective experience? From a clinical perspective, understanding the specific neural mechanisms of seizure patterns may lead to better diagnosis and more focused therapies, whether drug-based or surgical. If we succeed in understanding the fractures in consciousness caused by specific seizures, then we may also gain a better appreciation of the psychological challenges faced by our patients with seizure disorders. From a scientific perspective, separating specific neurophysiological components of consciousness is necessary to clarify the psychological functions of the neural mechanisms that regulate the brain’s large-scale networks. And from a philosophical perspective, we may find an opportunity to differentiate consciousness into functional components, rather than assuming it is an indivisible quality of mind. But perhaps the most important opportunity is the interdisciplinary one: We are working toward a scientific phenomenology in which an objective, biological analysis leads us toward a clearer appreciation of the bindings of consciousness in personal experience. Bibliography Edelman, G. 1989. The Remembered Present: A Biological Theory of Consciousness. New York: Basic Books. Holmes, M. D., M. Brown and D. M. Tucker. 2004. Are “generalized” seizures truly generalized? Evidence of localized mesial frontal and frontopolar discharges in absence. Epilepsia 45(12):1568–1579. Tononi, G., and C. Koch. 2008. The neural correlates of consciousness: an update. Annals of the New York Academy of Science 1124:239–261. Tucker, D. M., M. Brown, P. Luu and M. D. Holmes. 2007. Discharges in ventromedial frontal cortex during absence spells. Epilepsy and Behavior 11:546–557. Tucker, D. M. 2007. Mind From Body: Experience From Neural Structure. New York: Oxford University Press.
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From Treasury Vault to the Manhattan Project The U.S. War Department borrowed 14,000 tons of government silver in its drive to make the world’s first atomic bomb
Cameron Reed
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he U. S. Army’s World War II Manhattan Project was a drama unlike any other, with larger-than-life starring personalities, a supporting cast of more than 100,000, cutting-edge science, espionage and diplomatic intrigue. If that wasn’t enough, billions of dollars were gambled in the construction of enormous secret facilities to produce materials for a devastating weapon that might not work. All this played out against a background of worldwide conflict and the profound threat that Nazi Germany might achieve the world’s most powerful weapon first. Any compelling drama includes subplots, and the Manhattan Project was no exception. While the main veins of the science, engineering, ethics and geopolitical implications surrounding the development of nuclear weapons have been well mined by historians, some aspects of the Manhattan Project have attracted less study. Over the past few years I have researched several, including the so-called Silver Program. The program was fundamental to finding a means to safely and quickly produce the tens of kilograms of uranium necessary for a weapon of mass destruction. Cameron Reed is the Charles A. Dana Professor of Physics at Alma College, where he teaches courses ranging from first-year algebra-based mechanics to senior-level quantum mechanics. He received his Ph.D. in physics at the University of Waterloo in Canada. His research has included both optical photometry of intrinsically bright stars in our Milky Way galaxy and the history of the Manhattan Project. For his efforts in the latter, he was elected an American Physical Society fellow in 2009. Reed is the editor of the APS quarterly newsletter Physics & Society. His most recent book, The Physics of the Manhattan Project, was published by Springer in late 2010. Address: Dow 134, 614 W. Superior St., Alma, MI 48801. E-mail: _________
[email protected] 40
The secret government project to build the bomb was handed from the Office of Scientific Research and Development to the War Department in 1942. Management fell first to Colonel James C. Marshall of the Syracuse District of the U.S. Army Corps of Engineers. Marshall was ordered to establish a new district with no geographical boundaries. Its first offices were at the Atlantic Division headquarters on Broadway in New York City, hence the origin of the “Manhattan Engineer District” (MED), later called the Manhattan Project. Colonel (soon to be Brigadier General and later Major General) Leslie Groves was appointed commanding general of the new district in September 1942, a position senior to that of Marshall, who remained District Engineer until August 1943 when his deputy, Colonel Kenneth Nichols, replaced him. The paramount problem for the MED was finding means to produce sufficient enriched uranium for an atomic bomb. By early 1942, only milligram-scale quantities of uranium-235 (235U) had been isolated and it was by no means clear if any of the laboratory methods in use then could be ramped up to an industrial scale. Research into several techniques was fast-tracked and three ultimately were used at Oak Ridge. (A fourth approach to securing fissile material, synthesis of plutonium, was used in giant reactors located in Hanford, Washington.) From the beginning, electromagnetic mass spectroscopy was identified as a promising method, and it quickly became clear to Marshall and Nichols that massive quantities of copper would be needed for the magnets’ windings. But copper—used in shell casings—was a highpriority commodity during the war. So Marshall and Nichols struck on the idea of using silver as a substitute. Congress
had authorized the use of up to 86,000 tons of Treasury Department silver for defense purposes. Not having to divert mass amounts of copper was a huge boon for the project’s secrecy. Nichols met with Undersecretary of the Treasury Daniel Bell on August 3, 1942, to inquire about borrowing 6,000 tons of silver from Treasury vaults. In his memoirs, Nichols relates that Bell indignantly informed him that the Treasury’s unit of measure was the troy ounce— though not all present at that meeting recall any unpleasantness. Many MED documents do report quantities of silver in troy ounces and fine troy ounces. At 480 grains, a troy ounce is somewhat heavier than a common avoirdupois ounce, which weighs in at 437.5 grains. Fine troy ounces (FTOs) refer to the purity of the bullion: a 1,000 troy ounce “silver” bar of fineness 0.900 contains 900 FTOs of pure silver. For convenience, I quote weights in pounds of metal here after accounting for fineness. It is not uncommon to read Groves described as arrogant, arbitrary, insensitive, overbearing and high-handed. More appropriate labels might be mission focused and supremely competent. Groves graduated fourth in his 1918 West Point class and also trained at the Figure 1. The photograph at right, published in Life magazine in 1942, depicts silver being loaded at the West Point Bullion Depository in New York. The precious metal, Life reported, was being collected for an unspecified wartime industrial use. That same year, the U.S. War Department secretly started withdrawing tons of silver from the depository for the Manhattan Project, the secret government program that built the world’s first atomic bomb. That silver was shaped into coils and busbars, current-conducting strips, to operate a giant mass spectroscopy plant in eastern Tennessee. That plant processed the weaponsgrade uranium used in the bomb dropped over Hiroshima, Japan, in August 1945.
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Army Engineer School, the Command and General Staff School and the Army War College. His career in the Corps of Engineers was marked by steady advancement. When he assumed command of the MED, he was deputy chief of construction of the Corps of Engineers and was responsible for all domestic military construction. He had just overseen the building of the Pentagon and was well versed in the capabilities of large-scale contractors. It was Groves who selected J. Robert Oppenheimer to be the scientific director of the Los Alamos Laboratory, where the bomb was designed and built. The biographer Robert Norris described Groves as the project’s “Indispensable Man.” In Nichols’s blunter words: “General Groves is the biggest S.O.B. I have ever worked for. He is most demanding. He is most critical.… He is abrasive and sarcastic.… He is extremely intelligent … abounds with energy … if I had to do my part of the atomic bomb project over again and had the privilege of picking my boss I would pick General Groves.” Cyclotrons and Calutrons One of Groves’s first actions at the MED was to acquire a large tract of relatively isolated land in eastern Tennessee that
had been deemed suitable for establishing enrichment facilities. The army evicted some 1,000 families to take possession of a roughly rectangular tract of about 90 square miles, located 20 miles west of Knoxville, to establish the Clinton Engineer Works. The electromagnetic-separation plant, code-named Y-12, was to be built there. Construction of Y-12 was an enormous undertaking, requiring 67 million hours of labor by a workforce that peaked at about 20,000. The complex included more than 200 support buildings and required some 5,000 operating and maintenance personnel. Most had no idea what they were producing until President Truman announced that an atomic bomb had been dropped on Hiroshima. The need for so much silver at Y-12 emerged from the physics underlying electromagnetic mass spectroscopy. In an optical context, spectroscopy refers to using a prism to separate light into its constituent wavelengths. Similarly, mass spectroscopy separates atoms or molecules by their masses, with a magnetic field playing the role of the prism. The mass spectroscopes used at Oak Ridge were derived from Ernest O. Lawrence’s Nobel Prize–winning cyclotron, which he invented in 1931. Law-
Figure 2. Ernest O. Lawrence of the University of California at Berkeley examines the vacuum chamber of a 37.5-inch cyclotron in 1935. Lawrence won a Nobel Prize for this invention, an accelerator of subatomic particles that was fundamental to developing the field of nuclear physics. The chamber was placed between the poles of a big magnet that confined accelerated particles to circular trajectories. (Photograph courtesy of the Lawrence Berkeley National Laboratory.) 42
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rence’s original device had nothing to do with enriching uranium. He invented it in response to a growing crisis in nuclear-physics research. Throughout the 1920s nuclear physicists depended on purely natural phenomena such as alpha decay to supply the “projectiles” used to bombard target elements and induce reactions. But alpha particles (helium nuclei) arising from natural decays are of rather low energy and are readily repelled by the protons residing within the nuclei of even middleweight target elements. For practical purposes, experimenters were restricted to lighter target elements such as aluminum and magnesium. By the late 1920s, they were rapidly running out of potential targets and needed a means to artificially speed up the bombarding projectiles. Lawrence’s cyclotron opened a vast new experimental horizon for nuclearreaction researchers. In the device, two D-shaped metal vacuum tanks were placed back to back, with both perpendicular to a strong magnetic field. Ions injected at the center of the tanks were accelerated toward their sides by alternating the tanks’ electrical polarities at high frequency. Meanwhile, the magnetic field, enacting the Lorentz force law, would try to nudge ions into spiral paths. The ions consequently moved in spiral trajectories and would eventually strike the outer walls of the tanks where they reached targets set up to induce the reactions under study. Lawrence’s first cyclotron was about five inches in diameter. By 1939 he had developed one with a 60-inch diameter that required a 220-ton magnet. In Lawrence’s calutron (a contraction of California University Cyclotron), ionized and accelerated uranium tetrachloride molecules were released into vacuum tanks, which stood vertically between coils of massive electromagnets. Because the force that a magnetic field exerts on a charged particle is perpendicular to the velocity of a particle, the field can do no work on the particle. That is, its speed does not change but its direction does, a textbook application of centripetal force. That is what makes the ions’ trajectories circular. In this context, researchers discovered that the radius of a given ion’s orbit depends on the strength of the magnetic field, the extent of its ionization, the speed at which it enters the magnetic field and, most importantly, its mass. Ions of greater mass will travel in orbits of larger radii than those of lesser mass.
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In the case of uranium, two separate ion streams result: one for the rare, fissile isotope of atomic mass 235, which accounts for only 0.7 percent of natural uranium, and one for the common, nonfissile isotope of mass 238. Since the separation of ion streams is widest after only half an orbit, isotopes were collected there. Subsequently, 235U was chemically separated from the tetrachloride molecules. The design and power requirements of the calutron tanks were simpler than those of the cyclotrons because it was not necessary to generate an electric field inside the tanks. Despite the simplicity of this method on paper, a host of confounding issues arose at Oak Ridge. To sort uranium ions, the magnetic field needed to be very uniform. Molecules ionized differently than what was ideal for the radius of the vacuum tanks splattered against the tanks’ inner walls and had to be scraped out. The resulting collection efficiency was only about 10 percent. Random thermal variations in the ions’ initial velocities inevitably led to some mixing of streams, producing enrichment rather than separation. Complicating things even more, the mass difference between the two uranium isotopes is close to just 1 percent, meaning the stream separation was miniscule unless the magnetic field was extremely strong. And the like-charged ion streams repelled each other and hence displaced the trajectories from ideal curves. This effect limited production rates in individual vacuum tanks to a scant 100 milligrams of 235U per day. To produce the nearly 50-kilogram critical mass of 235U, Y-12 eventually was fitted with more than 1,000 tanks, many containing multiple ion sources. Alpha, Beta and Silver Lawrence and his Berkeley colleagues developed two basic designs for the Y-12 enrichers: Alpha and Beta units. Alpha units enriched uranium to about 15 percent 235U. That processed material was then fed to the Beta units, which enriched it to bomb-grade level, 90 percent 235U. This meant that the Beta units could be smaller, resulting in savings of power and precious materials. Continuous innovation was a hallmark of the Manhattan Project, and designs for both types of enrichers evolved considerably with experience. Early in 1943, Groves authorized construction of five Alpha-I enrichers containing 96 tanks with square-shaped coils. The components were arranged in www.americanscientist.org
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Figure 3. Construction of the electromagnetic complex called Y-12 was underway by 1943 at the top-secret Clinton Engineer Works in eastern Tennessee. In time, more than 1,100 calutrons were operating there, a process that required persistent troubleshooting and design changes to optimize an experimental technology that had never been scaled to industrial use. (Photograph courtesy of Y-12 National Security Complex.)
oval configurations called “racetracks.” But the tanks at the curved portions of the oval racetracks were difficult to regulate. In the fall of 1943 the enrichers were supplemented by four Alpha-II tracks, which also contained 96 tanks
but were laid out in a rectangular configuration with single units lined up on each side of the racetrack. Beta units contained 36 tanks laid out in a rectangular configuration and used D-shaped coils. Groves initially authorized two
Figure 4. At the Y-12 plant, calutrons were grouped together in large “racetracks” to maximize their productivity. Oblong tracks eventually were abandoned for a rectangular format. The large scale was needed because even though Manhattan Project technology was the best of its day, each calutron tank could collect very little fissile uranium at one time. (Photograph courtesy of Y-12 National Security Complex.) 2011 January–February
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alpha 1 racetrack
busbar magnet coils
electric field
uranium tetrachloride heated
ion collectors U-238
ion source
U-235
vacuum pump U-235
uranium tetrachloride heated ion source
U-238 electric field
ion collectors
Figure 5. By 1942 Lawrence and colleagues at Berkeley had modified the cyclotron to produce an electromagnetic mass spectrometer they called a calutron (California University Cyclotron). Uranium tetrachloride was vaporized with heat, which created positively charged ions. Those ions were accelerated by an electric field. Inside the vacuum tank, the resulting stream of ions was bent by a magnetic field. 238U, which has a slightly higher mass, makes a slightly wider trajectory than the sought-after 235U. That separated one stream into two.
Beta units but eventually approved eight, the last of which came on line after the war ended in late 1945. Eventually, nine Alpha and eight Beta units contained a total of 1,152 vacuum tanks. This is where all that Treasury Department silver comes in. The metal was needed to produce coils to make the calutrons’ giant solenoids, which produced a needed high-intensity magnetic field in accordance with the Biot-Savart law, which describes the strength and orientation of a magnetic field created by an electric current. For the Alpha units, the combination of practicable ion speed and magnetic field yielded ion streams about 3 meters in diameter with a maximum separation of just over a centimeter. Based 44
on a 3-meter side length for the coils and estimating 30 windings for each, one can calculate that the current that flowed through them must have been about 30,000 amperes. At its peak of operations in the summer of 1945, the Clinton Engineer Works consumed about one percent of the electrical power produced in the United States, much of it flowing through those silver coils. Secretary of War Henry Stimson formally requested the silver in a letter to Secretary of the Treasury Henry Morgenthau Jr. on August 29, 1942. Stimson gave no indication of what the silver would be used for, saying only that the project “is a highly secret matter.” His letter stipulated that the silver should be of fineness 0.999, that title would remain with
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the United States, and that any silver received by the War Department would be returned in the original quantity, form and fineness to the place from which it was removed. The stated deadline for returning the silver was five years from its receipt or upon written notice from the Treasury that all or any part of it was needed for reasons connected with monetary requirements of the United States. Stimson assured Morgenthau that the metal would be installed only in government-owned plants. The War Department eventually withdrew more than 400,000 bullion bars of approximately 1,000 FTO each from the West Point Bullion Depository in West Point, New York, a Treasury facility known as “The Fort Knox of Silver.” That amount is equivalent to the weight of about 7,500 midsize automobiles today or some 250 fully loaded World War II B-29 bombers. The first bars were withdrawn on October 30, 1942, and were trucked about 70 miles south to a U.S. Metals Refining Company facility in Carteret, New Jersey. The next day, the plant began casting the bars into cylindrical billets weighing about 400 pounds each. By the time casting operations ceased in January 1944, just over 75,000 billets weighing nearly 31 million pounds had been cast. Remarkably, this weight exceeded the 29.4 million pounds withdrawn from the Treasury, This was due to very careful cleanup operations of the fabrication facilities. Machines, tools, furnaces, factory floors and storage areas that had accumulated years worth of metal shards were dismantled and scraped clean. Any silver found was separated and cast back into bullion bars. Even workers’ coveralls were vacuumed clean. Armed guards observed every processing step to ensure that all trimmings were recovered. Scrap recovery and cleanup operations were so successful that over the course of processing, more than 1.5 million pounds of silver were collected and returned to Treasury, much of it likely originating from earlier and unrelated silver processing. That more than offset a much smaller amount—11,000 pounds—of borrowed Treasury silver that was unaccounted for. Once cast, the billets were trucked a few miles north to a Phelps Dodge Copper Products Company plant in Bayway, New Jersey. There the billets were heated and extruded into strips that were 3 inches wide by 5/8 inches
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West Point, NY West Point Bullion Depository 29,365,193 pounds withdrawn
Figure 6. Borrowed government silver made multiple stops on its journey from a U.S. Treasury facility in West Point, New York, to the secret Y-12 facility in Tennessee. At the Allis-Chalmers Manufacturing Company in Wisconsin, silver coils were unwound, soldered together and then wound under tension around the steel bobbins of magnet casings. (Photograph courtesy of Milwaukee County Historical Society.)
thick and 40 to 50 feet long. If all the Manhattan Project silver was shaped today into one strip of that same width and thickness, it would reach from Washington, D. C., to outside Chicago. After being cooled, the strips were coldrolled to various thicknesses depending on the particular magnet coils for which they were intended. Then they were formed into tight coils (not yet the magnet coils) that were about the size of large automobile tires. More than 74,000 coils were produced. Most were shipped to Wisconsin for magnet fabrication, but some 268,000 pounds were sent directly to Oak Ridge to be formed on-site into nearly 9,000 busbar pieces. The busbars were massive conductors about a foot square that carried current to the magnet coils. During their manufacture, armed guards again stood by, this time with pieces of paper positioned to catch drill dust as workmen bored holes in pieces of silver in preparation for fastening them together. The coil strips were shipped from New Jersey to Wisconsin by rail, usually in shipments of six sealed cars, with each shipment containing about 300 coils. The coils were under 24-hour guard—no fewer than three armed guards rode along in a special caboose www.americanscientist.org
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on each trip. At the Allis-Chalmers Manufacturing Company in Milwaukee, coils were unwound and joined together with silver solder to form larger reels, which were fed into a special machine that wound them around the steel bobbins of the magnet casings. Between February 1943 and August 1944, 940 magnets were wound. On average, each contained about 14 tons of silver. Those coils were then shipped to Oak Ridge on flatcars. These didn’t require guards because the silver was inside welded-shut steel casings. The pace of work at the Y-12 facility was swift. Ground for the first Alpha building was broken in February 1943, before the facility’s design was even complete and just as the first load of coils was being shipped to Tennessee. The first Alpha track started up just nine months later, on November Figure 7. It takes work to convert government treasure into industrial components. The borrowed government silver was shipped to multiple metal plants, by truck and by train, for processing. Silver scrap recovery practices mandated by Leslie Groves were so strict that the Manhattan Project recovered more silver from one New Jersey plant than it brought through the door, presumably from earlier projects involving silver at the facility.
Carteret, NJ United States Metals Refining Company 75,009 billets produced; melt loss: 1,378 pounds
Bayway, NJ Phelps-Dodge Copper Products Company 28,062,502 pounds extruded into 74,668 coils
2,717,586 pounds scrap recovery
Milwaukee, WI Allis-Chalmers Manufacturing Company 940 magnet coils, 27,418,294 pounds
268,745 pounds busbar
Oak Ridge, TN coils and busbars shipped to Y-12 facility at Clinton Engineer Works 2011 January–February
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Figure 8. The government hired young, female high-school graduates to operate the calutrons in Y-12. The women were trained to monitor meters and adjust dials, but they were not told what their equipment was producing. (Photograph courtesy of Oak Ridge National Laboratory.)
13, although its initial operation was short-lived. The windings shorted out because the coils were too close together and because an insulating oil was contaminated with organic material. Operations were halted, and 80 Alpha-I magnets had to be returned to Milwaukee for rebuilding. The second Alpha track entered service on January 22, 1944, and the rebuilt first track on
Figure 9. A worker removes a C-tank from a calutron in Y-12 in order to extract uranium. Because the process was inefficient, workers at the facility had to scrape uranium that didn’t make it to the ion collectors off the walls of the calutron tanks. (Photograph courtesy of Y-12 National Security Complex.) 46
March 3. By late January 1945, nine Alpha racetracks containing 864 calutrons and six Beta racetracks containing 216 calutrons were operating in eight sizable buildings within the Y-12 complex. Success and the Postwar Era The needed isotope accumulated gradually at Oak Ridge. By April 1945, the Y-12 facility had produced only 25 kilograms of bomb-grade uranium and, in conjunction with other enrichment methods, was producing more at about 200 grams per day. By mid-July the facility had produced slightly more than 50 kilograms. By this time Y-12 had consumed about 1.6 billion kilowatt-hours of electricity, about 100 times the energy yielded by the bomb called Little Boy, which was dropped on Hiroshima on August, 6, 1945. Essentially every atom of 235U used in Little Boy was processed in Lawrence’s calutrons. By the end of 1946, Y-12’s cumulative production amounted to just more than 1,000 kilograms of 235U, the equivalent of about 15 Little Boys. By late 1946, the gaseous-diffusion method of uranium separation was operating much more efficiently than the electromagnetic process, so uranium enrichment in all but one Y-12 building was shut down that December. The last of the Manhattan Project silver, however, wasn’t returned to West Point until June 1, 1970, just a few weeks before
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Groves died. Some of the Y-12 calutrons continued to be used to separate every element in the periodic table. After the war, many calutrons were refitted with copper windings. But not the calutrons in what was called the Pilot Plant. They operated until 1974— with 67 tons of silver in their magnet windings until 1970—to separate isotopes other than uranium, some of them used in the graphite reactor in nearby Oak Ridge National Laboratory. That facility created radioactive tracers used in medical tests, an example of wartime technology transformed into a humane use. Other calutrons developed for the Manhattan Project separated stable isotopes until 1998, when cheaper isotope sources forced the operation to close. Sadly, part of the reason that this country faces a shortage of medical isotopes today is because these facilities were shut down. With the transfer of Manhattan District assets to civilian control under the Atomic Energy Commission on January 1, 1947, Groves saw his influence on nuclear policies wane rapidly, helped in part by the fact that he had offended many influential people over the years. He served as chief of the Armed Forces Special Weapons Project for one year but resigned from the army in February 1948 to become vice president for research at Sperry Rand Corporation, a technology innovator with large contracts with the U.S. military. He held that position until his 1961 retirement. He is buried in Arlington National Cemetery. Ernest Lawrence continued his advocacy of government-sponsored “big science” projects after the war, including the development of fusion weapons. Frustrated with the slow pace of the fusion program, he teamed with theoretical physicist Edward Teller to lobby for a second weapons laboratory to complement and compete with Los Alamos. In response, Lawrence Livermore National Laboratory was established in California in 1952. In July 1958 President Eisenhower asked Lawrence to travel to Geneva for negotiations with the Soviet Union to develop a treaty banning nuclear weapons testing. The scientist’s long-standing chronic colitis flared up, however, and he was hospitalized. Lawrence died the following month. Element number 103, discovered in 1961 at Lawrence Berkeley National Laboratory, was named Lawrencium in recognition of his many contributions to high energy physics research.
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was worth the cost in civilian deaths and the resulting damage to America’s perceived moral standing. But without doubt, the Manhattan Project was the world’s first “big science” undertaking. It affected immediate and long-term events unlike any other science-based endeavor in history. The project and its silver program are exemplars of what sound science and engineering, when conducted by competent practitioners under superb leadership, can accomplish in a time of pressing need. One wonders whether a similar effort could be mounted today. Bibliography
Figure 10. Ed Wescott, an Army Corps of Engineers photographer, took this photo at Oak Ridge on Victory-in-Japan Day, August 14, 1945. Workers had finally learned what they had been doing at the facility: producing fissile uranium for a powerful new weapon. The dominant response at first was relief that war finally had ended. But some who labored there developed misgivings about nuclear weapons over time. (Photograph courtesy of Y-12 National Security Complex.)
Looking Backward and Forward Most of the original buildings in Los Alamos where the bomb was developed were torn down decades ago, but some have been preserved. Los Alamos National Laboratory is still the nation’s primary nuclear-weapons design center, employing more than 10,000 people employed in the stewardship of weapon stockpiles and the manufacture of plutonium cores. The three World War II–era plutonium production reactors at Hanford, Washington were shut down in the 1960s. Two have been sealed up in concrete shells but B-Reactor, the first plutonium production reactor, recently was declared a National Historic Landmark and is being converted into a museum. Environmental remediation at the Hanford site will continue for the foreseeable future. The Y-12 facility at Oak Ridge still operates as a Department of Energy “National Security Complex” under contract with the Babcock & Wilcox Company. As described in the April 2010 Nuclear Posture Review Report, the Highly Enriched Uranium Materials Facility was recently dedicated there as part of the facility’s mandate to retrieve and store nuclear materials. The ultrasecure warehouse replaces multiple aging buildings with one state-of-the-art storage facility. The report also advocated that a new uranium-processing facility should be built at Y-12 to come online in 2021. www.americanscientist.org
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As Richard Rhodes has written, the mammoth scale of the Clinton Engineer Works stands as testimony to the sheer recalcitrance of heavy-metal isotopes. It also testifies to Groves’s desire that this country develop such an unassailable advantage in the production of fission weapons that no country would ever consider a Pearl Harbor–type attack on the United States again. The numerical advantage was secured, though not everyone celebrated the result. Between 1945 and 2009 the United States built more than 66,000 warheads as various designs were developed, tested, deployed and eventually retired, with their fissile material reused in later generation designs. Disarmament treaties have reduced the number of weapons stockpiled in this country in recent decades, although the number of countries worldwide with nuclear weapons has increased. As this article was written, the National Park Service and the Department of Energy were preparing to submit to Congress a recommendation for a Manhattan Project National Historic Park that will include sites at Los Alamos, Oak Ridge and Hanford. It is my hope that the sites will remain accessible to help future generations explore and understand the project. Historians will forever debate whether it hastened the end of World War II or obviated a bloody invasion of Japan. Some are not convinced that hurrying the end of the war
Gosling, F. G. 2001. The Manhattan Project: Making the Atomic Bomb. Washington: Department of Energy. Groves, L. R. 1962. Now It Can Be Told: The Story of the Manhattan Project. New York: Harper & Row. Hewlett, R. G., and O. E. Anderson. 1962. A History of the United States Atomic Energy Commission. Vol. I. The New World, 1939/1946. University Park, PA: The Pennsylvania State University Press. Jones, V. C. 1985. United States Army in World War II. Special Studies: Manhattan: The Army and the Atomic Bomb. Washington: Center of Military History, United States Army. Logan, J. 1996. The critical mass. American Scientist 84(3), 263–277. Nichols, K. D. 1987. The Road to Trinity. New York: William Morrow. Norris, R. S. 2002. Racing for the Bomb: General Leslie R. Groves, the Manhattan Project’s Indispensable Man. South Royalton, Vermont: Steerforth Press. Parkins, W. E. 2005. The uranium bomb, the calutron, and the space-charge problem. Physics Today 58(5): 45–51. Rawlins, B. 1969. Borrowed Silver Worth $1 Billion One of Oak Ridge’s Epoch Secrets. Chattanooga Times, July 14, 1969. Reed, B. C. 2009. Bullion to B-Fields: The Silver Program of the Manhattan Project. Michigan Academician 39(3): 205–212. Rhodes, R. 1986. The Making of the Atomic Bomb. New York: Simon and Schuster. U.S. National Archives and Records Administration, Microfilm set A1218 (Manhattan District History), Reel 10, Book V (“Electromagnetic Project”), Volume 4 (“Silver Program”). Yergey, A. L., and A. K. Yergey. 1997. Preparative Scale Mass Spectrometry: A Brief History of the Calutron. Journal of the American Society for Mass Spectrometry 8(9): 943-953.
For relevant Web links, consult this issue of American Scientist Online: http://www.americanscientist.org/ issues/id.88/past.aspx
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Chromatin Evolving Despite our long familiarity with the chromosome, much about its function and evolution remains a mystery
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n 1897, the American cytologist Edmund Beecher Wilson of Columbia University published his great work, The Cell in Development and Inheritance. Wilson synthesized much of what had been previously observed and deduced about the hereditary role of the cell nucleus in the nearly 40 years prior to the rediscovery of Gregor Mendel’s work, which in turn would lay the foundations of modern genetics. After the independent rediscovery of Mendel’s laws of inheritance in 1900, Wilson’s colleague, Nettie Stevens, along with his students, Walter Sutton and Thomas Hunt Morgan, would go on to empirically confirm the role of the chromosome in both sex determination and the transmission of heritable information in living organisms. In later years, Morgan’s own students, Alfred Sturtevant and Hermann Muller, would become the first to map genetic mutations to chromosomes and to artificially induce mutations in the lab. Wilson’s masterful book combines meticulous observations of the microscopic activity of cells with logical insights derived from simple manipulations of cell specimens. It thereby reflects a unique period when biology was in transition from a science based largely on descriptive observation to a science grounded in carefully planned experiments. One of the most remarkable insights that Wilson derived from the reports of early experimentation was the Gregory A. Babbitt is an evolutionary biologist with primary interests in the evolution of eukaryotic gene regulation and statistical methods in molecular evolution. He received his Ph.D. in zoology from the University of Florida and is currently visiting assistant professor at Rochester Institute of Technology. Address: School of Biological and Medical Sciences, Rochester Institute of Technology, Rochester, NY 14618. E-mail: ________
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conclusion that the “idioplasm,” now called chromatin, is the physical seat of heredity. Chromatin is the complex of DNA and protein molecules that comprises chromosomes. Equally visionary was Wilson’s portrayal of chromatin as an active, dynamic substance in the cell nucleus. Cytologists of Wilson’s era observed clearly that chromatin moved about in the nucleus and that prior to cell division, chromatin changed radically, condensing from a diffuse mass into easily visualized compact threads. Wilson reproduced diagrams by the Italian cytologist Galeotti that documented further profound changes in chromatin in response to disease and environmental toxins. The dynamism of chromatin is sometimes forgotten in light of textbook portrayals of the chromosome as a static library in which the all-important genes are fastidiously shelved. In fact, acknowledging the dynamic nature of chromatin seems, in all eras, strangely at odds with chromatin’s potential role in heredity. How can something so apparently mutable on a cellular timescale also exist relatively unchanged over vast tracts of evolutionary time? Interpretation of the role of chromosomal dynamics in routine cellular functioning was largely set aside by biologists in the mid-20th century as they fixed their attention on the molecular basis of heredity, the new field laid open by the discovery of the chemical structure of DNA in 1953. A year earlier, Alfred Hershey and Martha Chase had demonstrated that nuclear protein was not the hereditary material and that DNA was the carrier of heritable information. Many of the experiments that elucidated the role of DNA were performed on bacteriophage, or phage—viruses that affect bacteria. The DNA of phage is not as-
sociated with proteins that package and control access to the DNA, and this contributed to the tendency to overlook chromatin structure as an integral element of genetic control. There was continuing interest in discovering the higher orders of structure of eukaryotic nuclear DNA—how was it wrapped, or stacked, or coiled at the highest levels—but for many years there were no answers, because the structural motifs of chromatin are far too small to image in detail by microscopy, yet they are not amenable to visualization by techniques such as x-ray crystallography, the workhorse in the era of visualizing macromolecules. Even the definitive work of François Jacob and Jacques Monod on the regulation of genes in bacteria helped propagate a textbook view of gene regulation in which chromatin structure made no contribution. According to the model of Jacob and Monod, genes are turned on and off by protein factors that bind directly to DNA sequences, thereby controlling adjacent genes. The picture seemed simple and complete without searching out a role for chromatin structure. Attention moved instead to the search for genecontrolling protein factors. Finally, the deceptively simple structure of the DNA molecule—a regular double helix, with all of its variability apparently confined to the sequence of its nitrogenous bases—seemed to imply, as Francis Crick noted in a 1953 letter to his son Michael, that the principle role of the cell nucleus was to store a large amount of digital information in the form of a four-letter cipher, and that it was the coding feature of the genetic material and not higher levels of molecular structure that determined how “life comes from life.” A basic problem with this view, especially regarding cells that package their
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Figure 1. This transmission electron micrograph shows DNA unspooled from its usual protein packaging after salt treatment has disrupted binding and charge interactions. In animal cells, DNA is tightly packaged with proteins, two loops per protein core, core upon core, to form fibers, cables and larger-scale structures of chromatin. After 100 years, we still don’t have a clear picture of those larger-scale structures. Recent studies, however, are revealing tantalizing glimpses of the architecture of chromatin, how chromatin organization contributes to gene regulation, and how chromatin structure may be sculpted, like any other physical feature of an organism, by evolution. www.americanscientist.org
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DNA into chromatin, is that the structural and biophysical features of DNA and DNA-protein complexes could hardly fail to have some effect on the expression of the information in DNA. The question is how much. Finding the answer requires that we look not just at the gross levels of chromosomal superstructure, but at the finest degrees of chemical and spatial distinction conferred, for example, by bends and twists in DNA, which pinch and widen the spiral grooves on the surface of the molecule and modulate the strengths of interacting charges along the molecule. Both effects change the binding properties of DNA. Modern biologists are particularly intrigued by the dynamic molecular functioning of the nucleosome, the basic building block of chromatin. Nucleosomes are formed when DNA wraps around a core particle of histone proteins. Most DNA in the cell is packaged in nucleosomes. Yet we still do not fully understand some of the most fundamental properties of
the nucleosome, including the way its position on DNA is determined, its roles in gene regulation and its potential impact on the evolution of regulatory systems in organisms. What is becoming clear is that, as first surmised over 100 years ago, a more complete picture of chromatin function at the largest and smallest scales will be critical in advancing our understanding of current questions in biology.
Looking Closer Appreciation of the roles of DNA shape, structure and binding properties in the control of gene activity is growing. Recent work by Remo Rohs and his colleagues in 2009, focusing in acute detail on the biophysics of DNA-protein interactions, demonstrated that DNA sequences containing short repeated runs of adenine (A) or its complementary partner thymine (T) actually have a slightly narrower and therefore stiffer helical structure. When DNA containing these short A tracts is deformed by bending, as required by most DNA-protein interactions, including those that occur in the formation of nucleosomes, the narrowing of the DNA’s minor groove focuses electrostatic potential in a nucleosome way that attracts the positively charged amino acid arginine. This
30-nanometer fiber
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Figure 2. This portrait shows Edmund Beecher Wilson in the 1920s. His textbook, The Cell in Development and Inheritance, was one of the founding documents of American cell biology.
attraction seems to explain how many transcription factors, which are often arginine-rich, can find their proper binding sites without reading base by base through the DNA sequence. Rohs and his colleagues also show that the same mechanism is active in the positioning of nucleosomes on DNA sequences. It is important that biophysical investigations like these on the fine structure of DNA receive attention alongside the recently ascendant bioinformatics revolution that stresses statistical analysis of DNA sequences. Figure 3. In the hierarchical structure of chromatin, DNA wraps around histones to form nucleosomes, which cluster to form a fiber 30 nanometers in diameter. The exact arrangement of histones in the fiber is unsettled, and the arrangement of fibers in higher-order structures is even murkier.
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Until very recently the nucleosome itself, formed by the tight winding of DNA around the highly evolutionarily conserved histone proteins of the nucleosome core, was regarded as simply passive “packaging” in which the information encoded in DNA could be comfortably warehoused until needed. Transcription factors, it was assumed, simply displaced the nucleosomes when it became time to access the critical regulatory sites on DNA. The study of transcription-factor binding has itself, until recently, been largely limited to this perspective, focused primarily on identifying base sequences that define particular binding sites instead of reflecting a more complete biophysical perspective that examines the propensity of a protein to interact with particular DNA sequences in terms of the molecular dynamics and binding energetics of both binding partners. In the ever-expanding ocean of DNA sequence data that has come to characterize our post-genomic era, we are relearning that DNA is a biophysical structure, with important implications for the nanometer-scale interactions between DNA and protein that underlie the regulatory networks of the genome. Nucleosome Positioning DNA is among the stiffest of biological molecules. The spiral winding of the double helix confers some rigidity, and the like-charged groups arrayed along the spine of DNA repel each other, contributing to the tendency of the DNA molecule to straighten. Biophysical calculations indicate that under physiological conditions of pH and salt concentration, a genome-sized length of unspooled DNA would not collapse into a minimal heap like thin sewing thread dropped on a tabletop; it would instead form a diffuse volume, more like a bushy mass of nylon fishing line. The volume of the mass would be many thousands of times the volume of the cell in which it must reside. The biological solution to this problem in most larger genomes is the spooling of DNA in snugly wound nucleosomes. The nucleosome consists of two pairs of four types of histone protein (H2A, H2B, H3 and H4) forming an octamer, or eight-unit histone core, that is wrapped almost twice by a 147base length of DNA. The molecular structure of the nucleosome was dewww.americanscientist.org
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Figure 4. One of several competing models for the local arrangement of nucleosomes into fibers is shown above. Undisputed is that nucleosomes aggregate tightly and that the interactions of nucleosomes with each other and with DNA are dynamic and responsive to cellular conditions. Histone cores are shown here as transparent meshes, DNA as low-resolution solidsurface models. (Structure coordinates courtesy of Daniela Rhodes.)
termined in 1997 by Karolin Luger at the Institute for Molecular Biology and Biophysics, ETH Zurich. Since then, slightly higher-order structures of chromatin consisting of multiple histones have been determined by others in the field, although we still cannot confidently describe the precise geometry of the cables of DNA known to exist in the cell, formed by millions of histones in a tantalizingly as-yetunseen array. Whereas primary chromatin structure is defined by the sequencedependent positioning of nucleosomes on DNA, the next level of chromatin structure is likely determined by the interactions of adjacent nucleosomes—interactions that are controlled through chemical modification of the histone molecule itself. In particular, the H3 and H4 histones have long tails that interact with the DNA sequences on the outside of adjacent nucleosomes. The acetylation of specific amino acids on the H3 and H4 histone tails tends to promote dissociation of tight nucleosome assemblies, resulting in open chromatin that is conducive to gene activation (by allowing transcription factors access to the DNA). Methylation of other sites is associated with closed chromatin
structure and repressed gene activity. Histone regions within the nucleosome core are also subject to specific modifications, which produce histone variants known to influence gene regulation. It has been recognized for several decades that the interaction of DNA with the nucleosome core seems to favor periodic sequence patterns of 10 to 11 bases; these patterns seem to facilitate the pronounced bending of DNA around the rim of the nucleosome. A series of elegant analyses on experimentally induced nucleosomebound DNA fragments from the laboratories of Jonathon Widom of Northwestern University and Eran Segal of the Weizmann Institute in 2006 helped to experimentally confirm and further define patterns of nucleosome positioning on DNA. In this work, the main periodic pattern appeared to consist of certain adjacent base pairings of dinucleotides (AA, TT and TA) in the DNA sequence that were favored where DNA sequences contact the surface of the histone core. It is now clear that the natural 10.4base period in the helical structure of DNA helps impart these 10–11 base pair periodicities, which somehow favor the deformation of DNA to the his2011 January–February
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equilibrium globule
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Figure 5. Iterative development of a technique called chromosome conformation capture, explained in the text, has given strong evidence that the chromosome is not in tangled disorder like spaghetti (a), a state known as an equilibrium globule, but is instead composed of tiers of folds upon folds, more like the mathematical object called a Peano curve, which fills space via tight turns, forming fractal globules, and then globules of globules (b). Seams between globules would permit a measure of access to the interior, similar to the sliding library shelves in (c). (Images in (a) and (b) courtesy of Leonid Mirny.)
fractal globule
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tone surface. Biophysicists are currently exploring the molecular forces in action during nucleosome formation and have even developed models that predict with considerable precision the energies required for any given sequence to deform to the histone core. What is truly remarkable in all this work is that nucleosome formation and positioning appears to be highly dependent on these biophysically favored patterns in DNA sequence, suggesting that the sequence of DNA actually encodes its own packaging into chromatin. Inferring the Evolution of Chromatin As molecular evolutionists, my postdoctoral advisor, Yuseob Kim, and I working at the Biodesign Institute of Arizona State University, in collaboration with biophysicist Michael Tolstorukov at Harvard Medical School, were particularly excited about this finding. It suggested that we might be able to pinpoint natural selection acting directly on DNA sequences related to chromatin organization in the genome. The fact that the biophysical aspects of chromatin structure appeared to be sequence dependent strongly suggested that chromatin structure itself is directly subject to the forces 52
of evolution. We felt that this represented a new calling for those of us working in the field of molecular evolution—we would devise novel statistical methods for inferring the action of natural selection on DNA sequence patterns in terms of how these patterns affected chromatin structure. In 2008, we published our first analysis of the molecular evolution of chromatin organization in a simple unicellular eukaryote, the yeast Saccharomyces. Evolutionary inferences about chromatin should generate predictions about the formation of nucleosomes on given DNA sequences. Our original methods relied on correlating given sequences with patterns of nucleosome formation as defined by a large library of nucleosome-bound fragments of DNA. In our more recent work, we use computational modeling of the deformation energies required for specific sequences to conform to the molecular structure of the nucleosome core. We have demonstrated that natural selection appears to have acted at the molecular level to conserve sequences that affect nucleosome positioning in the regulatory regions of genes. Subsequent work has demonstrated that the binding sites of many transcription factors in yeast appear to have evolutionarily
conserved chromatin contexts that may play significant roles in the subsequent spatial and temporal dynamics of gene activity. Higher Levels of Structure The difference in size between the fiber formed of bunched nucleosomes and the giant condensed chromosome that becomes visible before cell division is huge—three to four orders of magnitude. Yet we know very little about the tiers of structure that are surely maintained within the condensed chromosome or in the uncondensed chromatin. Are the fibers arranged in loops, or coiled like rope? We simply don’t have a clear picture. However, we have recently learned a great deal through a series of linked experiments in several labs. We don’t yet have a comprehensive three-dimensional structure of every coil of the genome, but in the last year we have acquired a compelling overall picture of the rules the genome follows as it folds. The original technique of chromosome conformation capture —“3C”— was devised in 2002 in the lab of Job Dekker at the University of Massachusetts. Addition of formaldehyde forms crosslinks between regions of
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genomic DNA that are close to each other in space, even if they come from remote parts of the same chromosome or from different chromosomes. After digestion of the DNA into fragments, the linked pieces are recovered and analyzed, which generates information about how local regions of the genome were folded. The next innovation was to circularize and add primers to the recovered fragments of DNA, greatly facilitating amplification and subsequent analysis. Circularized 3C, called 4C, led the way to 5C from the Dekker lab, or carboncopy 3C, which added massive parallel analysis to amplification. These computationally enhanced methods can identify all regions of the genome that are close to each other in space, providing a pointillist snapshot of global genome folding. To incorporate next-generation DNA sequencing, the Dekker lab in partnership with Eric Lander of the Broad Institute of Harvard and MIT devised the Hi-C technique, in which markers added before purification of the crosslinked DNA permit the creation of a contact map showing which sequences are near other sequences over the entire genome. Analysis of the whole-genome map of interactions, using polymer theory and computer simulations, reveals much about how the 2 meters of DNA in every human cell is folded to fit within a 5-micron nucleus. Probability analysis revealed that gene-rich regions on different chromosomes interact preferentially. Hi-C data also suggested two distinct “compartments,” one more compact, the other more open, with the open compartment likely corresponding to actively transcribed chromatin. Further analysis, performed in collaboration with the biophysics lab of Leonid Mirny at the Harvard-MIT Division of Health Sciences and Technology, assessed the probabilities of contacts between pairs of loci separated by varying genomic distances. From the emerging statistical model, a structural model developed by computer simulations in the Mirny lab took on detail. This was capped by a cunning deduction about the overall state of packing. Different predictions are expected about the content of the contact map if the packing of chromatin is as random as spaghetti—referred to as an equilibrium globule—or if it is packaged in a series of tight space-filling www.americanscientist.org
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Figure 6. In a current model of gene expression, “transcription factories” are semipermanent protein assemblies that form on active genes in regions of unpackaged DNA. The degree to which such sites may be specified by the same influences that direct the patterns of histone binding is a subject of current research. (Image courtesy of Wong Hua.)
curves, with small stretches forming globules that abut other globules to form globules of globules, and so on at higher levels of organization, a polymeric state called a fractal globule. Such a structure was first proposed about 20 years ago by Alexander Grosberg and colleagues. Computer simulations based on Hi-C data indicate the presence of fractal globule organization in chromatin. Simulations further indicate that the lack of tangling and the hierarchy of globules would facilitate a more dynamic chromatin, easily unfolding to permit access to interior regions, shown figuratively by the sliding bookshelf in Figure 5. The Evolution of Gene Regulation Evolution on the molecular or sequence level can be classified as ei-
ther structural or regulatory in its effects. Structural evolution refers to DNA mutations that ultimately affect protein structure. By definition these changes are restricted to the coding regions of DNA. Mutations on the third base positions of codons (the three-base words that code for specific amino acids) generally do not alter the amino acid that is placed in the protein sequence—these mutations are generally silent; they have no effect on protein structure. Mutations at other positions in the codon are not silent. This consistent feature of the genetic code has allowed molecular evolutionists to infer that natural selection has affected protein structural evolution simply by examining the ratio of silent to non-silent mutations and then comparing this ratio to the result we 2011 January–February
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Figure 7. One of the variables of organismal development is variability. In the transition from genotype to phenotype, there can be a surprising amount of stochastic noise—nature and nurture are joined by chance when inducible gene meets fluctuating environment. Degrees of regulatory robustness and compensation against environmental influence can be seen when comparing the facial symmetry of this aphid (left) and fruitfly (right). (Image at left courtesy of Gregory A. Babbitt.)
would expect if selection were neutral. However, inferring the action of selection on noncoding regulatory regions of DNA represents a much more challenging task, as noncoding DNA lacks a convenient marker like the promiscuous third base position of codons. The functional suitability of regulatory DNA sequences is ultimately determined by their ability to physically conform to the binding sites of transcription factors that modulate gene expression. The biophysics of these interactions must compete with biophysical forces driving nucleosome formation—transcription factors compete with nucleosomes for access to these regions of DNA. While this implies a generally repressive role for chromatin, some strongly positioned nucleosomes have been shown to configure binding sites in ways that make them more recognizable to transcription factors. Recent studies have also shown that all genes are flanked with nucleosome-free regions of DNA that are stiffer than average and not as easily wound around nucleosome cores. Located just up- and downstream of coding regions, these open segments of DNA allow easier access to transcription factors. In fact, according to a recent model that has received much attention, they may contribute to long-lived assemblies called transcription factories. These either develop on activated genes or activated genes migrate to them to be transcribed. A speculative model of a transcription factory is shown in Figure 6. Future methods for inferring the molecular evolution of regulatory sites 54
in the genome will eventually need to address all of the complex molecular interactions involved. This can be done by utilizing statistical and biophysical modeling. We will then be better able to explore the vast areas of noncoding regulatory DNA, dubbed the “dark matter” of the human genome, using the same currency that quantifies its basic functional organization—the biophysical properties that ultimately determine whether the DNA polymer can deform to the structure of the nucleosome core, thereby controlling access to any information the DNA might contain. Where Gene Meets Environment In most multicellular organisms, the process of development is utterly dependent on the precise timing and control of gene expression. Many key developmental genes are only activated in the growing embryo at temporally and spatially precise moments. Until now, most of the research on the evolution of gene regulation has focused on the molecular control of basic patterns in the development of overall body plans, the field known as evo-devo. Once a developmental stage is complete, the most important function of gene regulation is to enable the induction of particular classes of genes in response to changes in environmental conditions. Much of early animal development occurs in a buffered, protected environment such as a uterus or an egg. Later growth and development is typically much more sensitive to external condi-
tions, such as the health and nutrition status of the mother for nursing infants or the various stressors of the environment. It is a common misconception that our phenotypes—our measurable morphological or physiological traits— are primarily the products of either our genes or our environment, the so-called nature-versus-nurture dichotomy. Like so many dichotomies, this one is false. Complex phenotypes are always the developmental product of the many inducible genes acting during development in a given environment, a gene-environment interaction that is combined with a sometimes surprising level of random biomolecular noise, as visualized in Figure 7. Organismal biologists mapping genotype to phenotype must remain aware that nature, nurture and chance are never completely separable in the development of a given phenotype. If they were to ask where these interactions take place in the cell, the answer would be in chromatin. At its most primary level, nucleosome formation is sequence dependent and so, by its very definition, should be heritable. In a study published in Science magazine in April 2010, Ryan McDaniell and colleagues reported the discovery of heritable individual and allele-specific chromatin signatures in humans. In the same journal the following month, Shahaf Peleg and coworkers reported the involvement of chromatin modification (altered histone acetylation) in age-related memory loss in mice. Studies such as these have demonstrated that chromatin is both highly
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stable (thus heritable), and therefore relatively permanent on evolutionary timescales, and yet also highly dynamic, subject to environmentally induced change in the individual. Because chromatin structure is at once stable and dynamic, or “quasistable,” it serves as the primary interface for the meeting of gene and environment, and it is the most obvious place to look for evidence of the evolution of gene regulation. But how exactly is this dual role of the chromatin achieved at a molecular scale? Because fine-scale chromatin organization, defined by nucleosome positioning on DNA, is so dependent on the composition and spatial patterns of nucleotide sequences, heritable and thereby evolvable chromatin signatures are probably also largely confined to the scale of direct physical interaction with DNA. However, because chromatin is also reversibly modifiable at higher levels of structural organization, such as through chemical modifications of the histone tails, the nonheritable and dynamic component of chromatin is probably a characteristic of its higher-level organization, defined at molecular scales more distant from direct biophysical influences of DNA sequences. Ultimately, it is this hierarchical, layered and quasistable quality of chromatin that allows for the complex duality of its behavior. Thus, while research in recent years has demonstrated that at the primary level of the nucleosome, DNA can actually heritably encode for its own packaging, there has also been an increasing understanding that the higher-order structure of chromatin is more plastic, subject to experiential and age-related remodeling during the course of a lifetime. The simple fact that the incidence of most human diseases increases with age suggests that changes in chromatin-mediated gene regulation is likely to be a common component of disease. An initial step in investigating chromatin’s role in disease will be determining how the organization of chromatin actually affects gene regulation. This will require novel tests of molecular evolutionary inference, which can show us where chromatin function has been evolutionarily conserved between closely related species. Given the complexity of chromatin dynamics, such tests will probably need to be grounded in biophysical modeling of the molecular interactions that dewww.americanscientist.org
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fine the bending and binding of DNA to both transcription factors and histones, the two protein classes that govern gene regulation most directly. As more human genomes are sequenced, the disease associations of functionally important regions of evolutionarily conserved chromatin will be further investigated, not simply in terms of DNA sequence polymorphism, as in present-day genome-wide association studies, but ultimately in terms of the age-related chromatin modifications that accumulate during a lifetime. Hope lies in the fact that, unlike damage to one’s DNA, changes to one’s chromatin are often quite reversible, a property imparted by the very nature—stable yet dynamic—of chromatin’s complex structure. Research in the area of chromatin biology has seen a massive upsurge in the last few years. The new transdisciplinary field of epigenetics, encompassing any heritable change in phenotype or gene expression that is not directly caused by a change in DNA sequence, is now a major funding directive at the National Institutes of Health. The physical mapping of nucleosome positions in the human epigenome is rapidly becoming a reality. But this modern task has its roots long ago in a time when most biologists had not yet rediscovered Mendel’s laws of inheritance nor even established a vocabulary for our modern concept of the gene. Edmund Beecher Wilson wrote about the importance of the chromatin function and evolution in defining the boundary of genotype and phenotype in organisms: The idioplasm [chromatin] of every living species has been derived, as we must believe, by the modification of a preexisting idioplasm through variation, and the survival of the fittest. Whether these variations first arise in the idioplasm of the germ-cells, as Weismann maintains, or whether they may arise in the body-cells and then be reflected back upon the idioplasm, is a question on which, as far as I can see, the study of the cell has not thus far thrown a ray of light. Whatever position we take on this question, the same difficulty is encountered; namely the origin of that coordinated fitness, that power of active adjustment between inter-
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nal and external relations, which, as so many eminent biological thinkers have insisted, overshadows every manifestation of life. The nature and origin of this power is the fundamental problem of biology. —E. B. Wilson (1897), in The Cell in Development and Inheritance Bibliography Babbitt, G. A. 2008. How accurate is the phenotype? An analysis of developmental noise in a cotton aphid clone. BMC Developmental Biology 8:19. Babbitt, G. A., and Y. Kim. 2008. Inferring natural selection on fine-scale chromatin organization in yeast. Molecular Biology and Evolution 25(8):1714–1727. Babbitt, G. A., M. Y. Tolstorukov and Y. Kim. 2010. The molecular evolution of nucleosome positioning through sequence-dependent deformation of the DNA polymer. Journal of Biomolecular Structure and Dynamics; Current Perspectives on Nucleosome Positioning 27(6):765–780. Hubner, M. R., and D. L. Spector. 2010. Chromatin dynamics. Annual Review of Biophysics 39:471–89. Lieberman-Aiden, E., et al. 2009. Comprehensive mapping of long-range interactions reveals folding principles of the human genome. Science 326:289–93. McDaniell, R., et al. 2010. Heritable individualspecific and allele-specific chromatin signatures in humans. Science 328: 235-239. Rohs, R., et al. 2009. The role of DNA shape in protein-DNA interaction. Nature 461:1248– 1254. Segal, E., et al. 2006. A genomic code for nucleosome positioning. Nature 442:772–778. Tsankov, A. M., et al. 2010. The role of nucleosome positioning in the evolution of gene regulation. PLOS Biology 8(7):e1000414. Wilson, E. B. 1897. The Cell in Development and Inheritance. London: MacMillan and Co. Woodcock, C. L., and R. P. Ghosh. 2010. Chromatin higher-order structure and dynamics. Cold Spring Harbor Perspectives in Biology 2:a000596.
For relevant Web links, consult this issue of American Scientist Online: http://www.americanscientist.org/ issues/id.88/past.aspx
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Galaxies Harlow Shapley
L The article that begins on this page originally appeared in the January 1942 issue of American Scientist, the first issue of the then-quarterly magazine to carry the name American Scientist. The original article spanned 15 pages and ran to 6,000 words, so for reasons of space some of those words are redacted from the print version of the magazine. The full text can be found at American Scientist Online. Virginia Trimble is Professor of Physics and Astronomy at the University of California, Irvine, and is also affiliated with the Las Cumbres Global Telescope Network. She was a Sigma Xi National Lecturer in 1974–77 and has, at various times, held assorted offices in the American Astronomical Society, the International Astronomical Union, the American Physical Society, and the International Union of Pure and Applied Physics. She is currently a member of the Council of the American Association for the Advancement of Science and received her very first honorary degree ever from the University of Valencia (Spain) in 2010. Current research interests include structure and evolution of stars, galaxies and the universe, and of the communities of scientists who study them. The bean counters say this will be publication 683 accumulated since 1963. Address: Dept of Physics & Astronomy, University of Califoria, Irvine CA 92697-4575. 56
ike the galaxies themselves, the field of inquiry concerning galaxies is large and not easily surveyed in a brief article. It will be well to restrict the assignment and write only concerning a few selected topics. Let us first try a bird’s-eye view of our own Galaxy. The bird whose eye we would use needs to be a remarkable creature to reach the remoteness necessary for an outside look. We cannot use Cygnus, the Swan, that heads in full flight along the northern Milky Way, nor Aquila, the Eagle, nor the big-billed Toucan, the Flamingo, the Phoenix, the Goose, the Bird of Paradise, nor Corvus, the Crow. All these constellation birds are composed of stars that are bright neighbors of the Sun and distinctly localized far inside our own Galaxy. What we need is an observation point something like a million light-years distant, well outside the bounds of the enormous Milky Way system. It would be pretty satisfactory to settle our bird comfortably in the outer haze of stars of the Andromeda Nebula. If the observer be a contemporary of ours, he will be looking at our system in terms of eight thousand centuries ago. It has been that long since the radiation left the Sun and its neighboring stars on its way to the retina of the all-comprehending but quite imaginary bird now surveying us from the Andromeda galaxy. Such a temporal disparity, 8 x 105 years, is of no particular moment in our considerations of the galaxies; and short-term enterprises like the current Western civilization, or even the whole history of mankind, can be neglected in the cosmic panorama as too momentary, too fleeting, for a clear recording. It is well known that the Milky Way star system is a much flattened organization and that the Sun and planets are well inside. This interpretation of the Milky Way was pointed out one hundred and ninety years ago by Thomas Wright, a pioneer “bird’s-eye viewer” of Durham, England. He saw that the hypothesis of a flattened stellar system with the Earth near the central plane would satisfactorily ex-
plain the Milky Way band as a phenomenon of projection in such a system.1 Our hypothetical observer in Andromeda would see this flattened wheel-shaped system not from the direction of its rim, nor from the direction of its axis, but from an intermediate position, galactic latitude –21°. It would appear in projection, therefore, as an elongated object, perhaps with the axes of the rough ellipse in the ratio of about three to one. There would be a conspicuous globular nucleus of naked-eye brightness. We are almost certain now that our Galaxy is a great openwork spiral system of stars, perhaps not much unlike the system Messier 83, shown in Figure 1. But in linear measure it may be much larger than Messier 83. It has taken a long time to get conclusive evidence on the structure of our own system. We are badly located. There are obvious difficulties with residing inside. The meadow violet, no matter how bold and sensitive, is at a disadvantage in meadow topography compared with the bird hovering above. For more than a hundred years astronomers have struggled with the problems of the structure of the Galaxy. There have been many speculators, but also some hard and systematic observers. Sir William Herschel dominated this field throughout the early part of the nineteenth century. His surveys of star clusters and nebulae, his measures of brightness and positions of various celestial objects, his interpretations of the accumulating material were so important that he is appropriately considered the founder of sidereal astronomy. Before him the emphasis was on comets and planets and the positions and motions of near-by stars and the laws governing these motions. It was essentially solar-system 1 For an account of the early cosmic interpretations by Thomas Wright and Immanuel Kant see the highly interesting account by F. A. Paneth, The Observatory (June, 1941), pp. 71 ff.; also H. Shapley, chap. v, Immanuel Kant, 1724–1924 (New Haven, Yale University Press, 1925), E. C. Wilm, ed.
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Figure 1. This image of the southern spiral Messier 83 (above) was captured on a photographic plate by an optical telescope of the mid-19th century. At right, Harlow Shapley pictured on first page of the first issue of Sigma Xi Quarterly to be called American Scientist.
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astronomy that attracted the telescopes and the wisdom of scientists until this GermanAnglican organist of Bath devised some instruments; then astronomy turned outward to interstellar spaces. Sir William Herschel was considerably baffled by the problem of the structure of the Galaxy and by the relation of clusters and nebulae to the Milky Way. His successors made many notable contributions, photometric and spectroscopic, to knowledge of the nature of stars and nebulae, but still the large cosmic problems remained baffling. Increasing telescopic strength, however, and the accumulation of many kinds and types of observations, eventually led to less puzzlement about the stellar neighbors of the Sun and the nearer parts of Milky Way. The old but unproved concept that the spiral nebulae and their relatives were external galaxies, coordinate with our own Milky Way system, gradually became established. The dimensions of the Galaxy and of the universe approached clarification, chiefly through the power of the telescopes of American observa-
Figure 2. Also known as 47 Tuc, the southern globular star cluster 47 Tucanae helped Harlow Shapley deduce our solar system’s location in the Milky Way. 58
tories and the vision of European and American theoreticians. In clarifying some of the earlier puzzles, however, the astronomers only succeeded in opening vaster vistas for exploration, interpretation and wonderment. The net gain has been considerable. It is no longer believed that the difficulties of certain astronomical enterprises have definitely blocked the progress of inquiry. A hundred years ago a distinguished scientist (not an astronomer) gloated a bit over the pronouncement that one thing would certainly forever remain unknown, namely, the chemical nature of the stars! It was not many years before the spectroscope began to betray him. Up to the time of her death Dr. Annie Cannon had classified more than half a million stars in detail on the basis of the chemistry of their surfaces. A great deal is now known of the chemical constitution of a galaxy of a billion stars at a distance of ten million light-years. An elementary astronomical student can quickly learn, with the use of modern equipment, about the hydrogen, calcium, iron, magnesium, helium, carbon, and the like in stars that have never actually been seen except by use of the photographic plate. The moral of that bad ancient pronouncement about stellar chemistry is that it is not wise to be discouraged with the difficulties arising from our awkward location in the Galaxy. Eventually all the answers to all the questions you could now ask about Milky Way structure may be known. And, of course, then we would be wise enough to ask other questions that you could not answer, nor could we. Here are some the current questions, and, for some of them, preliminary answers. 1. Are the Sun and its planets in the middle of our discoidal Galaxy? They certainly are not. There are many lines of evidence which indicate that the center is far away in the direction of the region where the constellations of Sagittarius, Ophiuchus and Scorpio come together, thirty degrees or a little more south of the celestial equator in the thick of the bright star clouds along the Milky Way. My early study of the globular star clusters (a reproduction of an important one, 47 Tucanae, is shown in Figure 2) was instrumental in showing the observer that he is well out toward the rim of the wheel-shaped Galaxy. There may be some “subcenters” in other parts of the Milky Way, in far south Carina, for instance, and in Cygnus. But those conglomerations of stars appear to be important local structures within the great Galaxy that has its massive nucleus in the Sagittarius direction.
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Shaping Up Shapley: A Commentary Virginia Trimble
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arlow Shapley was the Copernicus of the Milky Way. Copernicus got our Earth out of the center of the solar system, and Shapley got the solar system out of the center of the Galaxy, though the methods the two used were very different; Copernicus carried out long calculations (pre-slide-rule and pre-logtables, not just pre-computer) which showed that a sun-centered model of the solar system could do just as good a job as an earthcentered one in predicting positions of the sun, moon and planets in the sky. Shapley looked at many variable stars (called Cepheids) in a class of star clusters (called globulars), measured their distances, and thereby showed that we live very far from the center of the system of clusters. It took a century before most astronomers were Copernicans, but only a few years for acceptance of Shapley’s picture of the Galaxy. Contrary to popular superstition, Copernicus needed almost as many epicycles as Ptolemy had used. And Shapley needed to make several assumptions and approximations that eventually ruled out his distance scale, while leaving his main conclusion intact. Although Shapley in due course became known as a world expert on galaxies (hence his article!) and served as President of the Commission on Galaxies (then called Nebulae and Star Clusters) of the International Astronomical Union (IAU), the story of his involvement with the concept was not entirely a happy one. He arrived at Mt. Wilson Observatory in 1914 with a Princeton Ph.D. earned for analyzing the light curves of eclipsing binary stars. And he was then a supporter of the concept of “island universes,” the idea that certain smudgy things in the sky were systems of stars comparable with our own Milky Way. Then Shapley’s own work of the next five years persuaded him that our Galactic star system was a factor of 10 or more larger than the previously accepted size and, therefore, that the spiral nebulae were most unlikely to be comparable systems. About a dozen different lines of evidence, many spurious (see Trimble, 1995), tied
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him to this view by 1920. This was the year when officers of the U.S. National Academy of Sciences invited him and Heber Doust (rhymes with soused) Curtis to present talks the same evening on “The Distance Scale of the Universe.” This they did, their honoraria of $150 each covering travel from Mt. Wilson for Shapley and from Lick Observatory for Curtis. The event is now usually called “The Curtis-Shapley Debate,” though the format was that of two lectures, not a debate.
The Wide Field Camera 3 on NASA’s Hubble Space Telescope captured this image of Messier 83 in August of 2009. The device’s wide spectral range—from ultraviolet to near-infrared—has enabled the discovery of many previously unknown stellar objects, including about 60 supernovae. (Image courtesy of NASA.) 2011 January–February
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Why is it that we seem to be so baffled about the structure and dimensions of our own system, although we bravely go out to distances of one hundred million light-years in our explorations of other galaxies?
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2. Is this Galaxy in motion as a unit? How it moves with respect to near-by galaxies is not yet very clear, but certainly it rotates around the Sagittarius nucleus. It does not rotate as a solid wheel, at least at our distance from the nucleus. It rotates more as the planetary system rotates; the planets nearer the Sun go more rapidly and complete their “years” in shorter times than the remoter planets. We think we can very definitely measure the differential speed of stars around the nucleus. The average speed in the Sun’s neighborhood is about two hundred miles a second, and the direction of motion is toward the northern constellation of Cygnus. 3. How far are the Sun and the neighboring stars from the axis of rotation? Ten kiloparsecs is the approximate answer and, since a parsec is 3.26 light-years or about twenty trillion miles, the distance is something like 2 x 1017 miles, or thirty-odd thousand lightyears. For various reasons, that value of ten kiloparsecs is not too certain, but it is well established that the center of gravity of our system is between eight and twelve kiloparsecs distant. The direction to the center is fixed with an uncertainty of only two or three degrees; this angular parameter is much easier to handle than the distance. 4. How large is the Milky Way system and how populous? Enormous in size and population, if non-quantitative terms may be used. There is good evidence that the total population in stars is of the order of two hundred thousand million, but the evidence on overall dimensions is as yet inconclusive. Indeed it is somewhat involved with definitions. For instance, what constitutes the boundary of a galaxy? Is it at the distance of the furthermost discoverable member of the system? Or is it the distance to the place where the number of stars per cubic light-year has decreased to a specified small quantity? Or is it, for a spiral galaxy, the distance to which a spiral arm can be traced? Or is it the distance to which an escaping star can go before the gravitational holdback is exceeded by the pull from some other galaxy? The diameter of the system in its plane is not less than a hundred thousand lightyears if all its recognizable stars are included. There is now good evidence that the wheelshaped system is surrounded by a more or less spherical haze of stars, and some of the stars in the haze are fifty thousand lightyears above the plane of the Milky Way. Probably this haze extends more distantly in the plane of the system and, therefore, the
diameter of discoid plus haze considerably exceeds one hundred thousand light-years. On the other hand, the diameter of our system in its plane might be measured as only fifty thousand light-years, or even less, if we had to depend on photographic research equipment which, although comparable with our own, was located in the Virgo supergalaxy, several million light-years away. Our outer stars might not register. When our telescopes are turned on the members of that group in Virgo we can trace on the best of our long-exposure plates the largest individual galaxies only to a distance of ten or fifteen thousand light-years from their centers. Either those systems are very much smaller than ours, or we are unable to explore the faint regions that are as remote from the nuclei as we are from our nucleus in Sagittarius. It might turn out, therefore, that the bird’seye observer from the Andromeda Nebula would report that our galactic system is no larger than the Andromeda Nebula; or, if the research were rather casual, the view might include only the nuclear portions of our galactic system, which might even be catalogued as a spheroidal galaxy. When we, in our turn, take a quick bird’s-eye view of the Andromeda galaxy, and measure its distance and dimensions, we immediately conclude that it is much smaller than we are, even though it is a giant compared with the average galaxy of our catalogues. But when the over-all extent of the Andromeda galaxy is studied with precise measuring apparatus, we double the dimensions as first seen and conclude that it is not very much smaller than the Milky Way system. 5. Why is it that we seem to be so baffled about the structure and dimensions of our own system, although we bravely go out to distances of one hundred million light-years in our explorations of other galaxies ? What is so troublesome about measuring something that completely surrounds us and is near at hand? That question finally brings out one feature of Milky Way structure which must be clearly seen at first glance by the observer in Andromeda, but which has taken us many years and much labor to discover and partially evaluate. This basic feature (and difficulty) is the presence throughout the Milky Way, especially near the Milky Way plane, of interstellar absorbing material—dust and gas, scattered and in clouds, around the stars and in the spaces between them. Our vision is not clear; simple geometric relations between light
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Curtis was expected to, and did, defend a picture of the Milky Way about 10,000 parsecs1 in diameter with us near the center, while Shapley plumped for up to 120,000 parsecs, with the sun 20 kiloparsecs from the center (but still very close to the midplane). In addition, Curtis said “Island universes, yes,” and Shapley said “Island universes, no!” In brief summary, Curtis was right about Island Universes, Shapley about our noncentral location, and our current number for the size of the Milky Way is close to the average of their two numbers. Within a year, both had moved. Curtis became director at Allegheny Observatory and later at Michigan. And Shapley was ensconced as director at Harvard Observatory by the time Edwin Powell Hubble announced the discovery of Cepheid variables in three of those smudgy, spiral things, called M33, NGC 6822 and M 31 (the Andromeda Nebula). He wrote to Shapley before the public announcement—scientists were gentlemen in those days, even when they were ladies. Shapley showed the letter to his then graduate student Cecilia H. Payne (later Gaposochkin) with the remark, “Here is the letter that destroyed my universe.” (Haramundanis 1996, p. 209) Neither Shapley nor Curtis ever again had access to a large telescope. Meanwhile Hubble went on to use the 100inch at Mt. Wilson, commissioned in 1917, to find Cepheids in more “spiral nebulae,” use them to calibrate other distance indicators, and to put his distances together with redshifts measured by Vesto Melvin Slipher at Lowell Observatory. He found a linear redshift-distance relation, now called the expansion of the universe. Shapley necessarily accepted this, but he does not sound enthusiastic about either the expansion or about the use of redshifts to determine galactic motion or membership in clusters. So, what had gone right and what wrong up to 1920, from 1920 to 1942, and since then? En route from Princeton to Mt. Wilson, Shapley visited Harvard, where Solon Bailey urged him to use the Mt. Wilson 60-inch (then the largest telescope in the world) to study 1
What is a parsec? It is the distance to a star from which an observer looking back at us would see the earth-sun distance to be exactly one arc-second on the sky. It is the official IAU unit of distance for things outside the solar system and handy for stellar astronomers because it is close to the average distance between stars near us. Galaxy sizes are typically kpc, distances between them Mpc and the size of the observable universe about 5 Gpc. 2 Encountering Solon in quick succession after Vesto Melvin, Heber Doust, and Harlow may leave you wondering where astronomer’s mothers found their names.
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Hubble’s Wide Field and Planetary Camera 2 recorded this natural-color image of globular cluster 47 Tucanae. A closeup of the central region shown in Shapley’s Figure 2, the image includes about 35,000 stars packed much more closely together than those in our area of the Milky Way. (Image courtesy of NASA.)
variable stars in globular clusters outside the plane of the Milky Way, rather than continuing his thesis work on eclipsing stars in the plane.2 The advice came at a critical moment. H. C. Plummer at Dublin and Shapley himself had just shown that the Cepheid variables could not be eclipsing binaries, because one star would have to be inside the other to account for the periods. Rather, they were pulsating as if breathing in and out, suggesting that they might all have the same physics. Then, if the correlation between periods and brightnesses seen for variables in the Large Magellanic Cloud in 1908–12 by Henrietta Swan Leavitt could somehow be calibrated, astronomers would be able to measure distances anywhere they saw these pulsating stars, for instance to establish the size of the Milky Way and our distance from its center. The majority of astronomers from William Herschel around 1800 to Jacobus Kapteyn and Curtis up to 1920 had thought we were very close to the center of a small stellar system. 2011 January–February
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A hundred globular clusters surround our galaxy, apparently subordinate members of the system, but the larger ones, like Omega Centauri and 47 Tucanae, should perhaps be ranked with the dwarf galaxies.
and distance are incorrect because our observing station is in a fog that unevenly dims the light of the surrounding stars. Gradually we are learning through studies of colors, and otherwise, how to make corrections for the interstellar absorption. It would not be difficult at all if the absorbing material were uniform. But the clouds of absorption are irregular. It is supposed that some of the greatest irregularities would be apparent to the Andromedan observer. At any rate, our own bird’s-eye views of hundreds of external galaxies show immediately the dark lanes between spiral arms, or across them, which indicate the interstellar absorption clouds that irregularly dim the star fields of those distant stellar systems. In summary, our imaginary bird’s-eye view has revealed our system as discoidal in its main body of stars, probably surrounded by a thinly populated spheroidal shell and dominated by a massive globular nucleus, which is some thirty thousand light-years from the Sun in an accurately measurable direction. Less certainly the view discloses that the Milky Way system is a spiral, perhaps more open in structure than the Andromeda galaxy; it is rotating at high speed, but even so two million centuries or possibly more will be required for the Sun and its neighbors to complete one circuit, to click off one cosmic year. Uncertainty remains as to over-all dimensions of the discoidal Galaxy and of its stellar haze, and this uncertainty arises in part from the light-absorbing, mostly nonluminous, interstellar material and from its irregular distribution and its dissimilar effectiveness on light at various wave lengths. ------------------If, for a more distant view of this part of the universe we go off into space several million light-years in a special direction, the Andromeda Nebula and our galactic system would look like a pair of galaxies, separated by only a few diameters. And in the same field, apparently also a part of our local group of galaxies, would be the great spiral, Messier 33. A closer inspection from this distant point, and a careful measurement of distances, would show several fainter galaxies associated with these three large systems. Two of them would be the faint companions of the Andromeda Nebula—Messier 32 and NGC 205; two of them would be our own satellite-companions, the Large and Small Clouds of Magellan. And there would be at least four other dwarf galaxies, two of them irregular in form, and two or more spheroidal.
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The existence of this local cloud of galaxies, in which our system appears to be the big dominating member, seems to be now beyond question, but the census of its membership is not complete. All the known members are within a sphere of a million light-years diameter. Those unknown, or of uncertain membership, include systems wholly or partly concealed by the clouds of absorption near the Milky Way plane. The rating of the great globular clusters is also not yet clear. A hundred globular clusters surround our galaxy, apparently subordinate members of the system, but the larger ones, like Omega Centauri and 47 Tucanae, should perhaps be ranked with the dwarf galaxies. In total luminosity and in mass they are comparable to NGC 205, the faint spheroidal galaxy in the Andromeda group. Our hypothetical Andromedan observer would probably record at least these two giant clusters as dwarf galaxies, if our own procedure with regard to classifying NGC 205 was followed. Groups like the local “supergalaxy” occur elsewhere in Metagalactic space. A dozen rich clusters are known, some of them with hundreds of members, and a score or two of small groups, similar to our own, are already on record. One such is a group of objects in Fornax, in which the brightest are spheroidal; in our group the brightest galaxies are spiral or irregular in form. Probably there are dwarf galaxies in the Fornax group, but as yet we have not identified them, nor have we found the Magellanic type. Because of the general tendency of the universe to expand and the galaxies and groups of galaxies to recede from one another, it may be that eventually we shall be able to say which faint objects in Fornax are members of the supersystem simply by determining their velocities in the line of sight. If the suspected galaxy is really much more distant than the average of the Fornax group, it will show a bigger “red shift” in the spectrum, a greater velocity of recession, and thus intimate the larger distance and non-membership. ........................ The future of research on galaxies probably depends not so much on the size of telescopes as on the speed and resolution of photographic plates and on other radiationregistering devices. But even without better facilities than those at present available, astronomers have plenty to do in galactic research, for within reach are a thousand million individual stars in our own Galaxy, and at least ten million other galaxies.
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Shapley attempted the essential calibration, using a method called statistical parallax. This had been invented and tried in 1913 by Einar Hertzsprung. To make it work, you need to know velocities of a group of stars along your line of sight to them, their apparent motions in the sky and that they are a homogeneous group with random real speeds. Four things went wrong. (1) Shapley could not include the non-random motion of rotation of the Galaxy (not discovered until 1926). (2) He assumed that there was no absorption of starlight in its travel to us (roughly right for the globular clusters; badly wrong for his calibrating Cepheids in the plane). (3) He had slightly bad luck with inaccurate measurements of small numbers by several other observers. And (4) he had decided that the cluster variables (now called RR Lyraes) were the same sort of beast as the Cepheids in the galactic plane and in the Large Magellanic Cloud. The net result was to make the Milky Way look much larger than it really is and the distance to other galaxies look smaller by factors of about three nearby and ten at larger distances. See Fernie (1969) for the details. The Milky Way numbers had been sorted out by 1942. But extragalactic distances used by Hubble in his redshift-distance relation, and by everybody else up until the mid-1950s, remained much too small. Thus it was that Shapley says our Local Group is dominated by the Milky Way, and other writers from the 1920s and later spoke of “cake and biscuits” or “if the others are Islands, the Milky Way is a continent.” The extragalactic distance scale improved in many steps (Trimble 1996) to what we now think is the right answer (to better than 10 percent) coming from a “Key Project” using the Hubble Space Telescope (Freeman et al. 2001). But, meanwhile, and it was a long while, other galaxies came out much too small, and the apparent age of the universe given by distances divided by redshifts, was about 1.8 billion years, less than the known age of the Earth, and of the Sun and other stars, when they began to be understood just after World War II. Getting this right, so that the Milky Way is merely a typical largish spiral in a 13.7 billion-year-old cosmos, is undoubtedly the most important change since the article was written. What else? First there were some things that he got much righter than you might reasonably have expected. The globular clusters Omega Centauri and 47 Tucanae are indeed either the remnant cores of dwarf spheroidal (dSph) galaxies or some intermediate class of object. We say this now because they show several populations of stars of different ages and chemical compositions. None of those data existed in www.americanscientist.org
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Messier 83 takes on a significantly different appearance when far-ultraviolet (blue) and near-ultraviolet (green) recordings from NASA’s Galaxy Evolution Explorer are composited with radio emissions (red) from the National Science Foundation’s Very Large Array in New Mexico. (Image courtesy of NASA/JPL-Caltech/VLA/MPIA.)
Chandra X-ray Observatory captures yet another side of Messier 83. The bright orange central region is dense with neutron stars and black holes, enveloped by a cloud of gas at about 7 million degrees Celsius. (Image courtesy of NASA/CXC/U. Leicester/U. London/R. Soria and K. Wu.) 2011 January–February
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Hubble’s Wide Field Camera 3 focused on the center of the giant star cluster Omega Centauri, showing about 100,000 of as many as 10 million stars in the galaxy overall. (Image courtesy of NASA.)
1942, though he should have known better than to attribute Annie J. Cannon’s spectral types to surface compositions of stars, because his own student, Cecilia Payne, had shown that the main cause was different temperatures. Shapley’s final point about detectors being more important than bigger telescopes is also correct. In 1942, there was the 100-inch (2.5 meter) at Mt. Wilson, and the pieces of what would become the Palomar 200-inch bogged down in various places. The largest we have now are 10-meter mirrors, a factor of four increase in diameter and of 16 in “lightcollecting power.” Meanwhile, the efficiency of detectors has increased by something like 350, from an efficiency of 0.1 percent for turning photons into silver grains on plates to 35 percent for turning photons into electrons in 64
CCD cameras. Since you can’t get better than 100 percent, we are of course now coveting larger mirrors! It should be said, however, that Shapley was not a fan of large telescopes. His “large” southern reflector must have been a 36-inch, and many of the plates from which he convinced himself that most galaxies live in groups and clusters came from even smaller facilities. These show larger patches of sky than 100inch plates can, and Shapley said on occasion that Hubble’s problem, in concluding that most galaxies are scattered at random across the sky, was that his telescopes were too big! Other changes, not all of enormous importance, have occurred in astronomy and in astronomical writing since 1942. Shapley clearly expected his readers to be more familiar with the night sky than most of our current Sigma Xi colleagues are, including some astronomers for whom Cygnus is a box on the sky best observed in the summer, if they think about it at all. Candlepower as a synonym for brightness or luminosity would also have been more familiar. Our current students are entirely puzzled by the phrase “standard candle,” probably never having noticed that nearly all real candles are nearly the same brightness. Why this is so was put to me as a lunch-time question by Richard Feynman years ago, and it is left as an exercise for the reader to figure it out. There are surely other aspects of the writing style that you young folks will be more aware of than I. My mother was born the year after Harlow Shapley, about 300 miles away, and was one of my best friends until her 1984 death. Scientific progress can be approximately divided into observations (data) and theory (understanding). Many of the observational developments since Shapley wrote were entirely predictable, given better detectors on larger telescopes. At last count, the Local Group had about 37 members rather than seven, the new ones being a mix of dwarf irregulars and, mostly, dSphs. Some were found on photographic plates from the Palomar Observatory Sky Survey, often by Alan Whiting (who has a Ph.D. from Cambridge but is now the Third Assistant Engineer on a ship), many more from the Sloan Digital Sky Survey (SDSS) using CCD cameras. The Sloan folks publish in committees, but let me just mention James E. Gunn, who conceived, built and guided the project for many years, and Heidi Newberg, first author on a few of the papers, because I like them.3 The numbers of imageable and known stars, other galaxies and clusters of galaxies have all increased by orders of magnitude, including individual stars in other galaxies and dSphs in
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quite distant clusters. The motion of the Milky Way has been established accurately, though it took the discovery and mapping of the 3Kmicrowave, black body, cosmic background radiation to do it. In principle, this motion could also have been derived from accurate values of redshifts for very many galaxies in all directions. Galaxies are indeed essentially all grouped and clustered, even ones in volumes of the universe with less than average density. And dwarfs are the commonest sort, found everywhere you can look faint enough. On the theoretical side, Shapley says nothing about formation and evolution of galaxies and large-scale structure, now quite possibly the single largest subfield of astronomy and cosmology. Sir James Jeans in 1942 had things to say, mostly about gravitational contraction and what we now call the Jeans mass (so did he, but not in public) that were at least on the right track. The topic is now largely tackled by comparing SDSS-type observations with computer simulations that start with mass elements of dark matter and follow their interactions and sweeping up of hydrogen and helium gas. Although the phrase “dark matter” first appeared in print in 1922, it then meant very faint stars and perhaps gas and dust. Shapley does not mention it as part of the Milky Way or other galaxies. When he says that Omega Cen and 47 Tuc have the same luminosity and mass as the then-known dSph galaxies, he means just the mass belonging to the stars that radiate the light. The discussion of very bright stars is perhaps the least satisfactory part of the article to modern eyes. Brightnesses of supernovae, novae and what are now called Hubble-Sandage variables are distorted by varying amounts by the distance-dependent errors in Shapley’s distance scale. He supposes that novae must be important in the great scheme of things and supernovae not, because the former are also much more common, and because he thinks that novae might be used as distance indicators. In fact supernovae are essential to the buildup of all the other elements from hydrogen and helium, and one class (called Type la supernovae) is now our best “meter stick” at multigigaparsec distances. Novae are minor nuclear
bombs on the surfaces of white dwarfs with ordinary companion stars. He notes correctly that they must recur and has, mercifully, abandoned the nova mechanism he supported in the 1920 debate, where a nova occurs when a previously existing star moves into a previously existing gas cloud. The discussion of S Doradus, P Cygni and similar stars has, and could have had, no sense that these are associated with regions where massive stars are currently forming, because he wrote at a time when the majority of astronomers did not actually think that star formation was an ongoing process. Shapley’s article is now nearly 70 years old, and my first one goes back a smidge less than 50 years. How many of my early ones would I volunteer to have read and criticized somewhere around 2035? Well, maybe the one on Cheops pyramid from 1963. One’s first thought is that at least history papers don’t go out of date. But this is not entirely so. Shapley makes two historical remarks, one about Thomas Wright’s recognition of the disk shape of the Milky Way and one about the significance of the “novae stellae” of 1572 and 1604 studied by Tycho and Kepler. A modern historian of science would probably want to adjust both, to point out that Wright’s total universe had some much-less-realistic components and that the SN 1604 event came after Kepler had already been appointed Imperial Astronomer at Prague, following the death of Tycho. References Fernie, J. D. 1969. The period-luminosity relation: A historical review. Publications of the Astronomical Society of the Pacific 81:707. Freedman, W. H., et al. 2001. Final results from the Hubble Space Telescope key project to measure the Hubble constant. Astrophysical Journal 553:47. Haramundanis, K., Editor. 1996. Cecilia PayneGaposchkin, 2nd edition. Cambridge University Press. Smith, H. A., and V. Trimble. 2007. Harlow Shapley. In Biographical Encyclopedia of Astronomers, ed. T. Hockey et al. Springer, p. 1048. Trimble, V. 1995. The 1920 Shapley-Curtis discussion: Background, issues, and aftermath. Publications of the Astronomical Society of the Pacific 107:1133. Trimble, V. 1996. The incredible shrinking constant 1925–1975. Publications of the Astronomical Society of the Pacific 108:1073.
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Probably I should take warning from C. H. PayneGaposchkin (Haramundanis p. 227) that it is dangerous to believe one’s colleagues’ results because one likes them. She had in mind the acceptance by Shapley of Adriaan van Maanen’s claim that he could see rotation in the plane of the sky of some spiral nebulae, which would have made it impossible for them to be located outside the Milky Way. www.americanscientist.org
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Above is a series of images of molecular components of a commonly used laboratory cell line called HeLa. Researchers at the The Institute for Lasers, Photonics and Biophotonics at the State University of New York at Buffalo combine two imaging technologies, coherent anti-Stokes Raman scattering and two-photon excited fluorescence to observe proteins, lipids, DNA and RNA in the cells. Color images were made by overlaying signals of RNA (green), lipids (gray) proteins (red) and DNA (blue). Color images are succeeded here (from top to bottom) by the cells’ RNA, lipids, proteins and DNA, shown in separate channels. The first two in the series above are growing (interphase) cells, the second two are dividing (mitotic) cells and final two are cells engaged in apoptosis, which is regulated cell destruction. 66
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Mapping Macromolecules in Cells Researchers at the State University of New York at Buffalo are using advanced biophotonics to observe multiple types of macromolecules at once in living cells. The Institute for Lasers, Photonics and Biophotonics, directed by Paras N. Prasad, was first to apply this technology to monitor the distribution of native proteins, lipids, RNA and DNA during apoptosis, or programmed cell death. The work was published in 2010 in the Proceedings of the National Academy of Sciences of the U.S.A. More applications are in development. Artem Pliss, an institute research assistant professor, described the method and its promise to American Scientist associate editor Catherine Clabby. A. S. What are the technologies you used? A. P. Aliaksandr Kachynski and Andrey Kuzmin here in Buffalo designed and operate our multiplex setup. With it, we integrate two advanced nonlinear optical modalities: coherent anti-Stokes Raman scattering (CARS) and two-photon excited fluorescence (TPEF). CARS records the vibration frequencies of molecular bonds after they are exposed to intense bursts of light. We can use CARS to image protein and lipid macromolecules in cells, but the RNA and DNA vibration frequencies are barely distinguishable. So we selectively stained RNA and genomic DNA with fluorescent dye and used TPEF to image those macromolecules in two different fluorescent channels. The combination of technologies permits the characterization and monitoring of intracellular molecular organization at a level of sensitivity and complexity that previously was unachievable. A. S. How does this contribute to the practice of cell imaging? A. P. Traditionally, cellular organization is studied by the imaging of particular macromolecules tagged by fluorescent markers, which captures their distribution and interactions. This conventional technique, however, omits the locations of millions of unstained macromolecules, inherently limiting our understanding of cellular organization. In our study, we developed this hybrid approach, in which the specific molecules are mapped by TPEF simultaneously with the mapping of the cell’s proteins by CARS. The combination provides insights
into the dynamic transformations of the cellular structure. In the apoptosis study, we observed proteins change from being distributed nearly uniformly in the cell nucleus to being present in progressively irregular patterns, a transition not described before this study. A. S. Can you give an example of how this will be useful? A. P. This can be used to observe different organelles that accommodate specific biochemical activities. Revealing the macromolecular patterns in these structures can serve as a real-time indicator of cellular physiological condition. Our approach will also be valuable for monitoring the subcellular configuration of macromolecules during drug-cell interactions, which could facilitate drug development. A. S. What improvements are coming? A. P. We are working on expanding our imaging by adding several other optical modalities. Our aim is to simultaneously acquire diverse layers of information, such as the distribution, interactions, local concentrations and interface properties of different types of macromolecules. That will give more comprehensive characterization of the molecular structure in cells and tissues. We anticipate that our technology will be used for noninvasive molecular diagnostics as well as for drug development, where it will allow researchers to collect specific information on intracellular structure and enable high-throughput drug screening at the level of individual cells.
In Sightings, American Scientist publishes examples of innovative scientific imaging from diverse research fields. www.americanscientist.org
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2011 January–February
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Unraveling the Significance of Childhood Michael E. Lamb THE EVOLUTION OF CHILDHOOD: Relationships, Emotion, Mind. Melvin Konner. xvi + 943 pp. The Belknap Press of Harvard University Press, 2010. $39.95.
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elvin Konner’s The Evolution of Childhood caps a distinguished career, which began in the 1960s with an important piece of fieldwork among the !Kung San, nomadic hunter-gatherers who live in the Kalahari Desert. That study had a dramatic effect on both anthropology and developmental psychology, in part because its ethological observations, methods and conclusions influenced a generation of scholars, including John Bowlby, the father of attachment theory. Although the !Kung way of life had been affected by Western practices and material by the time Konner’s team (led by the eminent anthropologist Irven DeVore) conducted their seminal fieldwork, the project was of considerable importance to evolution-minded behavioral scientists. The hunting-and-gathering lifestyle of the !Kung was believed to provide insight into how the first humans (also hunters and gatherers) behaved in the environment in which our species evolved and to which Homo sapiens is thus adapted. Konner’s observations of !Kung infant life, and especially of infant-mother relationships, feature prominently in this new book, but his goal is much more ambitious: to synthesize all the literature bearing on the evolutionary emergence of our species, and especially on the ways in which humans came to raise their children. The breadth of vision he displays is extraordinary. Konner summarizes a considerable body of research on human evolution, beginning with paleontological and archaeological work on the emergence of life-forms and continuing through evidence regarding the emergence of mammals, primates, hominids and early humans, until finally Homo sapiens enters the scene. The volume is a singular achievement, not least because it encompasses, and describes accessibly and eloquently, many fields of endeavor and scholarship, ranging from molecular biology and interpretation of the geological record, to the interpretation of bone fragments found in
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archaeological sites, to observational research on the behavior of contemporary humans in a wide variety of ecological niches. Furthermore, Konner does not limit himself to secondary sources, as many might do when attempting to place their own research in broader context. Instead, he lucidly discusses a vast range of primary sources. The book’s 753 pages of text are accompanied by 159 pages of references. The goal may be extraordinarily ambitious, but the exercise must be deemed a remarkable success. Konner achieves a readable and persuasive synthesis more inclusive than anything ever before attempted. His account of human evolution, and especially of the evolution of childhood, is coherent and compelling. Of course, given the breadth of materials and disciplines it spans, the portrait painted offers a personal perspective, reflective of some selectivity. When discussing some topics, for example, especially those furthest from his own line of research, Konner does not make reference to all the latest arguments and materials—an inevitable compromise when the canvas is so large. Furthermore, his account perhaps understandably privileges the research conducted by scholars based at or associated with Harvard, the institution where he studied for many years. Studies carried out by Konner’s colleagues (including many who were, like him, members of the multidisciplinary teams that studied the !Kung in Botswana) are described more sympathetically and in much greater depth than the work of other researchers. Of course, the studies conducted by DeVore, Robert LeVine, Beatrice Whiting, John Whiting, Marjorie Shostak, Patricia Draper and Sarah Hrdy (to name but a few on the distinguished roster) indeed made profound and lasting contributions, but readers with particular interest in the topics explored by these scholars may be disappointed by the relative inattention to other important research conducted by later generations, especially of anthropologists and
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psychologists, who were not part of the Harvard extended family. Konner’s chief focus is, of course, on human childhood, although his analysis is extraordinarily well contextualized by reference to the ancillary fields documenting key transitions in the evolutionary process. He draws attention to the fact that upright bipedal locomotion offered many advantages to our socially living, hunting-and-gathering ancestors, but notes that these advantages came with a price—notably, a narrowed pelvis that made it necessary for parturition to occur when offspring were still extremely immature. In essence, this meant that the “fourth trimester” of fetal development took place outside the womb, and the increased child-care demands increased women’s needs for social protection and support, thereby promoting sociality, pair-bonding and the nascent family. These in turn made even longer periods of dependent and protected development possible, perhaps explaining why our species is characterized by an extended period of brain growth and development, which continues over a much greater proportion of the life span in humans than in any other primates. Long, protected childhoods, group living, enduring social bonds, and big brains not only made extensive play possible but also ensured that it paid benefits in terms of intellectual sophistication and cognitive mastery, justifying the “sapiens” label to which our species lays claim. Humans have, of course, always been distinguished by their behavioral flexibility, a degree of adaptability that has allowed them to occupy an extraordinarily diverse range of ecologies, including icy, windswept terrains that differ in every respect from the warm savannah where the species likely evolved. Despite this flexibility and adaptability, Konner argues, our species is characterized by a large number of behavioral universals, many organized around the fundamental features of child care, and many revealing gender dimorphisms. His arguments in this regard may be more controversial than his more extended synthetic analysis of evolutionary history. In particular, some readers may be more comfortable with the list of content-free “universal” processes (such as habituation, mimicry, attachment and cultural construction of perception) that are summarized in table 29.3 than with the list of content-laden features (such as coy or flirtatious behavior, personal property, parental devotion, depression and male abuse of power) that are represented as cultural universals elsewhere in chapter 29 and in other parts of the book as well. Furthermore, psychologists in particular will be uncomfortable with the inattention to variability and individual differences—especially because references to their existence are overshadowed by the emphasis on universal regularities. www.americanscientist.org
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MOSQUITO EMPIRES: Ecology and War in the Greater Caribbean, 1620–1914. By J. R. McNeill. Reviewed by David Arnold. McNeill demonstrates that differential immunity to mosquito-borne diseases such as yellow fever and malaria played an important role in the military and political history of the Greater Caribbean
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ATOMIC OBSESSION: Nuclear Alarmism From Hiroshima to alQaeda. By John Mueller. Reviewed by Hugh Gusterson. Readers of all political persuasions will find things to be annoyed at in Mueller’s argument that both the dangers and the importance of nuclear weapons have been exaggerated
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THE HADZA: Hunter-Gatherers of Tanzania. By Frank W. Marlowe. rLIFE HISTORIES OF THE DOBE !KUNG: Food, Fatness, and WellBeing Over the Life-Span. By Nancy Howell. Reviewed by Melvin Konner. These superb books tell us much about what it is like to live by foraging for wild food on an open plain in a warm climate
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SACRIFICE ZONES: The Front Lines of Toxic Chemical Exposure in the United States. By Steve Lerner. Reviewed by Lauren Byrnes, Sarah Mele and Daniel Faber. Lerner describes 12 communities whose residents, plagued by pollution from some of the most environmentally hazardous sites and facilities in the United States, are fighting for their right to a clean and healthy environment
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THE CYBERNETIC BRAIN: Sketches of Another Future. By Andrew Pickering. Reviewed by Brian Hayes. Pickering has deeply engaging stories to tell about the lives and work of six men who were key members of the British cybernetics community
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CLIMATOPOLIS: How Our Cities Will Thrive in the Hotter Future. By Matthew E. Kahn. Reviewed by David Satterthwaite. Kahn is confident that market forces, human ingenuity and economic growth will support adaptation to climate change and has little use for the idea that government could have a constructive role to play
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DANCE OF THE PHOTONS: From Einstein to Quantum Teleportation. By Anton Zeilinger. Reviewed by Peter Pesic. In a tour de force of exposition, Zeilinger explains with verve and charm how quantum effects are made visible and measurable in experiments
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SEEKING REFUGE: Birds and Landscapes of the Pacific Flyway. By Robert M. Wilson. Reviewed by Jared Farmer. Wilson recounts the history of governmental efforts to provide wetlands where birds can sojourn during migration
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ESCAPE FROM THE IVORY TOWER: A Guide to Making Your Science Matter. By Nancy Baron. rEXPLAINING RESEARCH: How to Reach Key Audiences to Advance Your Work. By Dennis Meredith. Reviewed by Elsa Youngsteadt. Baron and Meredith offer tips for scientists wanting to improve their ability to explain and promote their research
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THE CALCULUS OF SELFISHNESS. By Karl Sigmund. Reviewed by Cosma Shalizi. Sigmund provides an excellent introduction to the use of evolutionary game theory to investigate reciprocity, says Shalizi
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A STATE OF CHANGE: Forgotten Landscapes of California. By Laura Cunningham. Reviewed by Anna Lena Phillips. Drawing on 30 years of research and field observation, Laura Cunningham uses paintings and sketches to portray California’s ecological history
2011 January–February
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Meanwhile, social anthropologists may be unsettled by Konner’s understandable depiction of the !Kung experience as the definitive hunter-gatherer lifestyle, the one used to represent ancestral realities—and by his relative inattention to variations among contemporary hunter-gatherers, which at the very least underscore human adaptability in the face of contrasting ecological demands. There is also likely to be controversy surrounding Konner’s analysis of the evolution of culture— a concept still less accepted than the broader Darwinian model of evolu-
tion. To his credit, he offers a model that draws on many of the competing theories, but this is unlikely to be the last word on the evolution of culture. Indeed, it would be naive to expect “the last word” on issues as complex and timeless as those with which Konner grapples here. Nevertheless, this magisterial book is assuredly the most important analysis of the evolution of childhood yet attempted. It summarizes 40 years of observation, analysis and synthesis by one of the most profound thinkers of our generation. Whoever follows intellectually will necessarily
HISTORY
A Tale of Vectors, Viruses and Victims David Arnold MOSQUITO EMPIRES: Ecology and War in the Greater Caribbean, 1620–1914. J. R. McNeill. xviii + 371 pp. Cambridge University Press, 2010. $94.99 cloth, $24.99 paper.
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osquitoes live brief but busy lives feeding on nectar and plant sugars. The females must also find human or animal blood to feast on in order to produce eggs and continue the life cycle, so they live rather longer than the males—several weeks rather than several days. Frail though individual mosquitoes appear, historically they have shown an impressive propensity to travel. Sometimes they have been stowaways on ships traveling to other continents, carried aboard in water casks and drinking vessels. On arrival in new lands they have exploited the ecological changes—deforestation, canal building, rice cultivation, urban water storage and deficient drainage— brought about by their obliging human hosts. Despite occasional suspicions that mosquitoes were up to no good, most human observers before 1900 were remarkably unaware of the insects’ true role. They were inclined to regard mosquitoes as a nuisance—often a prodigious one—rather than the deathdealing menace they actually were. The creatures’ frailty belied their fatality. As accomplished environmental historian J. R. McNeill brilliantly demonstrates in Mosquito Empires, for nearly 400 years the human history of the Americas, from the northern shores and interior plains of South America through the islands of the Caribbean to the southeastern corner of the present-day United
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States, was governed by the activities of “imperial mosquitoes”—both the Anopheles species that were the vector for malaria and more especially Aedes aegypti, which harbored lethal yellow fever virus. His central argument is that when Europeans first established themselves in the Americas in the 16th century, they had an epidemiological advantage in that the diseases they brought with them (such as smallpox, measles, mumps and whooping cough) caused devastation among indigenous populations. But in the 17th century, migrant mosquitoes such as Aedes aegypti were introduced to the Americas, largely through the mechanism of the transatlantic slave and sugar trade, with ships serving as “supervectors, efficiently moving both mosquito and virus from port to port.” Once new diseases such as yellow fever made the crossing from West Africa, transported by mosquitoes or traveling in the blood of their victims, then the disease ecology of the Americas was profoundly transformed. Major demographic and environmental changes were also taking place—hundreds of thousands of slaves were imported, and forests were cut down for fuelwood used to boil sugar. The once benign Caribbean became a “giant sinkhole” of suffering humanity. The broad lines of this epidemiological transformation are already well known, to medical historians at least. Where McNeill excels is in demonstrat-
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build on this magnificently eloquent and integrative edifice. Michael E. Lamb, professor and head of the Department of Social and Developmental Psychology at the University of Cambridge, specializes in the study of social and emotional development, and the determinants and consequences of adaptive and maladaptive parental behavior. He is the author or editor of a number of books, including The Role of the Father in Child Development, which is now in its fifth edition (Wiley, 2010), and Tell Me What Happened: Structured Investigative Interviews of Child Victims and Witnesses, which he coauthored with Irit Hershkowitz and Yael Orbach (John Wiley and Sons, 2008).
ing, through a close reading of contemporary sources and of modern medical literature, how specific environmental changes in the Americas—especially the “ecological turbulence” caused by land clearance, plantation agriculture and urban expansion—created conditions in which immigrant diseases and their insect vectors flourished, and in which the differential immunity or resistance so central to this story began to operate. McNeill wisely eschews the overemphasis on race that has plagued many previous discussions of these issues, drawing attention instead to the formative role of specific environments (in Africa as well as the Caribbean) and of prior disease exposure. As he notes, by the late 17th century, individuals who had been born or had grown up in those areas of the “Greater Caribbean” (see map on facing page) in which malaria and, above all, yellow fever were rife likely either had an inherited immunity or had acquired protection through exposure to the diseases in childhood, when they were less often fatal. The epidemiological advantage now rested with the locals, whatever their racial composition, as opposed to those arriving unprotected from Europe or from relatively fever-free parts of the Americas. Many Europeans disembarked from ships only to go straight into their graves. Worse still, McNeill reminds us, medicine was no solace to the sick: The medical treatments employed at the time, including copious bleeding, or venesection, only worsened the patient’s condition, just as confinement in a hospital stuffed with fever-sufferers was bound to hasten an already imminent death. McNeill presents compelling evidence for the overwhelming mortality—especially from yellow fever—that
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devastated invading forces during this period, rendering them unfit to fight or to hold their position once gained. Casualty rates as high as 80 percent or more were seen in some of the forces involved in the British assault on Cartagena in 1741 and the siege of Havana in 1762. The defending forces, however, were shielded by their immunity and survived relatively unscathed. A further achievement in this compelling tale of vectors, viruses and victims is the subtle use of ecological insight to inform the political and military history of the region, without recourse to crude determinism. Like several other recent historians, McNeill draws upon scientific knowledge of the El Niño event and the wider ENSO (El Niño/Southern Oscillation) phenomenon to explain dramatic shifts in weather patterns and the proliferation of mosquito-friendly—and therefore disease-conducive—conditions. Through a series of deft case studies, he shows how political and military leaders unwittingly created situations in which the disease factor became decisive or shaped the strategic thinking of opposing armies. Even though they were unable to identify the cause of epidemics or to reliably predict their occurrence, people widely recognized that a new “ecological-military order” had come into being. Thus the Spanish, entrenched across a large part of the Greater Caribbean by the mid-18th century, were able to defend their domains by building fortifications that would delay the English and French long enough for the rainy season to begin and the invaders to be incapacitated by disease. And in one of McNeill’s most edifying examples, the American rebels’ evasive tactics, aided by disease, made it impossible for the British to regain control of the Carolinas during the Revolutionary War. With an army debilitated by malaria and largely confined to the fever-prone coast, Cornwallis was forced to capitulate at Yorktown in 1781. McNeill wryly observes that the tiny female Anopheles quadrimaculatus, one of the 30 or so malariatransmitting mosquito species, deserves to be ranked among the “founding mothers of the United States.” It is the subtle but lucid manner in which McNeill explores the multistranded relationship between physical environment, insect agency and human decision making that makes Mosquito Empires such a persuasive piece of hiswww.americanscientist.org
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The Greater Caribbean includes the Atlantic coastal regions of North, Central, and South America as well as the Caribbean islands—the places that in the 17th and 18th centuries became plantation zones, from Surinam in northern South America to the Chesapeake Bay. The evolving ecologies of the Greater Caribbean were excellent incubators for the mosquitoes that transmit yellow fever and malaria—breeding and feeding conditions for mosquitoes generally improved when a plantation economy was established. Once yellow fever and malaria became common in the Americas, residents acquired some immunity to them, but it became hazardous for outsiders to come to the region. Large-scale settlements and military expeditions often experienced devastating epidemics because people’s immune systems were unprepared. From Mosquito Empires.
torical writing. Before the 1890s, generals and guerrillas appear to have had little idea, other than a vague notion of “climate,” as to what caused epidemic mortality. Wily defenders and “canny revolutionaries,” however, had a limited understanding of differential immunity and used it to great practical effect. More than that, McNeill is able, as few have done before him, to connect all these episodes, from the English conquest of Jamaica in the 1650s through the sieges of Cartagena and Havana, the disastrous Scottish and French settlement schemes in Panama and Guyana, the catastrophic Anglo-French interventions in St. Domingue, the wars of American independence and the final eclipse of Spanish power in 1898.
He renders them into a cogent narrative, ending with the final dethroning by modern medical science of mosquito rule after 400 years of turbulent history. This is a remarkable book for its scholarship, but it is also a very readable one. In relating insect-borne disease to the ebb and flow of human history, it shows how effectively science can be written into history. David Arnold is Professor of Asian and Global History at the University of Warwick in the United Kingdom. He has written extensively on the history of modern India and on medical and environmental history, and is the author of several books, including The Tropics and the Traveling Gaze: India, Landscape, and Science 1800–1856 (University of Washington Press, 2006). 2011 January–February
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NUCLEAR POLICY
Atomic Escapism? Hugh Gusterson ATOMIC OBSESSION: Nuclear Alarmism From Hiroshima to al-Qaeda. John Mueller. xvi + 319 pp. Oxford University Press, 2010. $27.95.
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eading John Mueller’s Atomic Obsession is like going through the looking glass with Alice. Examining the conventional wisdom about nuclear weapons from the other side of the looking glass, Mueller tells us that their destructiveness has been exaggerated; that the bombings of Hiroshima and Nagasaki were of marginal importance in ending World War II; that “nuclear weapons have been of little historic consequence,” and that the United States and the Soviet Union would not have gone to war even in the absence of nuclear deterrence; that arms-control treaties are usually a waste of time and effort; that the dangers of nuclear proliferation are greatly exaggerated; that sanctions aimed at stopping countries from seeking nuclear weapons make it more likely that they will pursue them; and, finally, that “the likelihood a terrorist group will come up with an atomic bomb seems to be vanishingly small.” In arguing against atomic “alarmism” and the inclination “to wallow in a false sense of insecurity,” Mueller has something to annoy everyone. Conservatives can take umbrage at his arguments that the bombing of Hiroshima was unnecessary to end World War II and that the Cold War nuclear buildup was not needed to deter the Soviets. Liberals can be upset by the claim that arms-control treaties are pointless and sometimes even counterproductive. The challenge in reading Mueller’s book is to separate insights that are deviant but useful (some of his deconstructions of the conventional wisdom are genuinely insightful) from arguments that are deviant because they are exaggerated, misshapen or just plain wrong. Many of Mueller’s sharp-edged points about the hyping of the dangers of nuclear proliferation and terrorism fall into the first (insightful) category, but his critiques of arms control and his apparent smugness about all nuclear dangers belong in the latter. Mueller argues that liberals and conservatives have joined in exaggerating the danger and importance of nuclear 72
weapons; they have used our fears over the years to justify unnecessary weapons programs and arms-control negotiations, a counterproductive invasion of Iraq, and now bloated counterterrorism initiatives. He builds his argument atop an exercise in counterfactual history, maintaining that nuclear weapons were unnecessary to keep the peace during the Cold War, because both superpowers would have been deterred from war anyway by memories of the carnage of World War II, and because the Soviet Union was too risk-averse to chance an invasion of Europe. (He does not ask whether Soviet nuclear weapons might have deterred the United States from starting a war with the Soviets.) Those who know Cold War history in its rich complexity will be infuriated by the simplifications, omissions and blithe assumptions in this exercise in intellectual casuistry, which brings to mind not the work of a scholar seriously weighing evidence, but the efforts of a high-school debate team to push a contrived point of view as far as possible. The most original, incisive and interesting part of the book is the last third, in which Mueller slashes through the hype that guides much public discourse and policymaking about the risk of nuclear terrorism. He points out that a foreign government is unlikely to give a nuclear weapon to a terrorist group because of the danger that, as supplier, that country would invite retaliation against itself. He also uses the writings of several nuclear scientists, including the former Los Alamos division leaders Carson Mark and Steve Younger, to argue that it would be prohibitively difficult for a small terrorist group that lacked state sponsorship to acquire the subtle engineering knowledge needed to overcome the technical challenges involved in turning black-market nuclear material into a workable nuclear weapon. Many scientific experts not cited here by Mueller would take issue with that argument. And having read one of the articles that Mueller does cite—“Can Terrorists Build Nuclear Weapons?,” by J. Carson Mark and others (1987)—I am of the opinion that it does not, in fact, sup-
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port Mueller’s argument. Furthermore, in dismissing the case for a terrorist nuclear threat, Mueller does not adequately address the possibility that a terrorist group seeking a bomb might have access to a scientist with nuclear-weapons experience from another state as an adviser or team member. Still, by pointing out the importance of tacit and esoteric knowledge to the success of such an endeavor, Mueller is making an important challenge to glib assumptions about the ease with which a terrorist group, even if it had access to uranium and plutonium, might be able to make a bomb. Mueller fails to discuss another possibility: that a rogue element within a state, not the state leadership itself, might sell an intact nuclear weapon to which it has access. This scenario is far from speculative: After the fall of the Berlin wall, a Soviet soldier guarding nuclear weapons in East Germany offered to sell an atomic warhead to the antinuclear organization Greenpeace; Greenpeace wanted to buy the weapon and display it to show the dangers of nuclear proliferation. They were arranging payment and transportation when the warhead in question was abruptly removed from East Germany by the Soviets. It is, sadly, all too typical of Mueller’s style of argument that he makes his case with copious references to any literature that supplies evidence supporting his point of view, but he ignores inconvenient facts and arguments. We see something similar in Mueller’s discussion of arms-control treaties. He regards such treaties as bureaucratically unwieldy and argues that states often only agree to them when they involve no real sacrifice or merely codify what the state already intended to do. He bases this argument largely on a discussion of the Limited Test Ban Treaty of 1963, which forced nuclear testing underground but did nothing to curtail the nuclear arms race, and the Strategic Arms Limitation Talks Agreement (SALT I), which limited missiles but not the newly miniaturized warheads packed several to a missile, which were the real problem. Mueller has cherry-picked his treaties here. Why not discuss the Outer Space Treaty, which preempted a nuclear arms race in space? And what about the 1988 Intermediate-Range Nuclear Forces (INF) Treaty, which eliminated an entire category of nuclear weapons from Europe, much to the chagrin of hardliners in both superpowers? Above all, why not discuss the 1972 Anti-Ballistic Missile (ABM) Treaty (the existence of which,
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astonishingly, is never mentioned in Mueller’s book)? The ABM Treaty was widely seen by arms-control advocates as having headed off an expensive and destabilizing race between offensive and defensive weapons during the Cold War. The strengths and weaknesses of Mueller’s argument collide most jarringly in his discussion of nuclear proliferation. He is entertaining when he catalogs decades of dire predictions from experts about a coming cascade of countries crossing the nuclear threshold—predictions that have failed to come true, although this has not deterred contemporary pundits from re-sounding the alarm. And we need to think seriously about his argument that sanctions intended to deter nuclear proliferation killed hundreds of thousands of civilians in Iraq and North Korea while increasing the attractiveness of nuclear weapons to the paranoid leaders of those countries; the remedy may be worse than the disease. But surely Mueller goes too far, and his polemical casuistry becomes dangerous, when he argues that sanctions and treaties are largely unnecessary because most countries have freely eschewed proliferation, recognizing that nuclear weapons are “militarily useless, and a spectacular waste of money and scientific talent.” Although he is surely right that nuclear weapons are overrated and often fail to bring the bargaining power and military strength their owners seek, some countries (whether because they are in a bad neighborhood or have a bad regime) have spared no expense to seek them. And when a country acquires them, this puts pressure on rivals and neighbors to seek them too (as Pakistan did in response to India, for example). There can be a collective logic that forces individual countries to make choices they would rather not. The importance of the Treaty on the Non-Proliferation of Nuclear Weapons, for which Mueller shows so little respect, is that it releases countries from the prisoner’s dilemma here: The treaty and its inspection provisions give confidence to countries who want to eschew nuclear weapons as long as they can be sure that their rivals do so too. This is why Brazil and Argentina both joined the treaty regime in the 1990s, for instance. In short, Mueller has a gimlet eye for hype about nuclear weapons but is blind to their very real dangers. His book, which should sport a “don’tworry-be-happy” smiley face rather than a scrawled atom on the cover, www.americanscientist.org
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counsels us in its final sentence that we are not in danger and should “sleep well.” Mueller seems to assume that, because there has not yet been an accidental nuclear war, because terrorists have not yet exploded a nuclear weapon, and because no country has used nuclear weapons since the United States bombed Nagasaki, we are safe. Presumably BP executives talked the same way about the safety of deepwater drilling before April 20, 2010; Soviet engineers talked the same way about the safety of their nuclear reactors before April 26, 1986; and NASA engineers talked the same way about the safety of shuttle launches at low temperatures before January 28, 1986. In regard to nuclear weapons, we have arguably been lucky. There have been several incidents in which U.S. planes carrying nuclear weapons have crashed or burned. In 1995 the Soviets mistook a Norwegian weather rocket for a U.S.
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nuclear attack, and Boris Yeltsin found himself staring into the nuclear briefcase as his aides told him he might only have a few minutes to launch Russian nuclear weapons. And we now know that in the early years of the Cold War, there were senior U.S. military officers who wanted to preemptively attack the Soviet Union. Mueller mocks those who warn of events that are possible but have not happened. “There is a ‘genuine possibility,’” he says, “that Osama bin Laden could convert to Judaism, declare himself to be the Messiah, and fly in a gaggle of Mafioso hit men from Rome to have himself publicly crucified.” If only nuclear disaster were that unlikely. Hugh Gusterson is professor of anthropology and sociology at George Mason University. He is the author of People of the Bomb: Portraits of America’s Nuclear Complex (University of Minnesota Press, 2004).
ANTHROPOLOGY
At the Cutting Edge of Human Adaptation Melvin Konner THE HADZA: Hunter-Gatherers of Tanzania. Frank W. Marlowe. x + 325 pp. University of California Press, 2010. $65 cloth, $27.50 paper. LIFE HISTORIES OF THE DOBE !KUNG: Food, Fatness, and Well-Being Over the LifeSpan. Nancy Howell. xii + 234 pp. University of California Press, 2010. $60 cloth, $24.95 paper.
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he few societies that still live by foraging for wild food are of great interest to researchers curious about how our ancestors might have lived before the introduction of agriculture thousands of years ago. Two groups that have been intensively studied are the Hadza people of Tanzania and the !Kung San (also known as the Jun/twasi) of the Kalahari Desert. The Hadza continue to hunt and gather today—two attempts at settling them ended in disastrous epidemics and a return to the hard but viable life they are so good at. The !Kung way of life has changed in recent years, but much information was obtained about them in the 1960s and 1970s, when they were still living as hunter-gatherers. Two recent books—Frank W. Marlowe’s The Hadza: Hunter-Gatherers of Tanzania and Nancy Howell’s Life Histories of the Dobe !Kung: Food, Fatness, and Well-Being over the Life-Span—show how much
the Hadza and the !Kung have in common. As someone who spent two years studying the !Kung San as a member of Harvard Kalahari Research Group expeditions in 1969–1971 and 1975, I found both volumes riveting. Modern work on the Hadza was pioneered by James Woodburn in 1958. Later, Nicholas G. Blurton Jones, joined by Kristen Hawkes, James O’Connell, Frank Marlowe and others, led decades of studies motivated by neo-Darwinian theory. Marlowe’s book is based on 15 field trips he made to Tanzania, during which he spent a total of four years with the Hadza, and on dozens of published papers, including his own. It is the most important single source of information about the Hadza, and it is superb, combining many of the virtues of classical ethnography with rigorous quantitative description and experimental hypothesis testing. The book is dedicated “to the Hadza, the fantastic, wonderful 2011 January–February
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The digging stick, which may have been one of the first tools used by hominins, is still quite important to tropical foragers today. It is the main tool of Hadza women, who begin using the wooden sticks at age 2. The sticks vary in length because they become blunted and have to be repeatedly sharpened with knives. Here, Hadza women accompanied by young girls dig tubers. The digging requires strength and stamina; some of the species of tubers that the Hadza eat grow in rocky spots, and boulders sometimes have to be moved to get at them. From The Hadza: Hunter-Gatherers of Tanzania.
Hadza,” and to Blurton Jones, “simply the greatest adviser one could ever have.” It was Blurton Jones whose vision made study of the Hadza a proving ground for evolutionary theory. The Hadza occupy an area of about 4,000 square kilometers around Lake Eyasi, a large body of salt water in northern Tanzania. It is remarkable how much they resemble the desert-dwelling traditional !Kung, given the differences in their environments. It is also striking how well both societies fit the generalizations made by Richard Lee and Irven DeVore in Man the Hunter in 1968. Marlowe’s excellent comparative chapter, in which he puts the Hadza in the context of all other hunter-gatherers for whom data are available, further confirms most of these generalizations. Both the Hadza and the !Kung live in small groups with a mean size of about 30 people. These groups move camp several times a year for various reasons, including the availability of food and water. Groups are larger in the dry season and smaller in the rainy season. They are basically egalitarian—any attempts at domination fail, because people gain others’ support or simply leave the group if someone tries to boss them around. There is no role specialization 74
except the division of labor by sex, and male domination is minimal. There are no clans or rules of inheritance passing through one sex, but groups are made up mainly of various kinds of kin. Violence can erupt between two men over a woman, and this is a main cause (among the Hadza, the main cause) of homicide. Meat supplies about 25 to 30 percent of the calories in both diets, and most aspects of child care are very similar between the two cultures. To a former !Kung researcher, it is reassuring to see these and many other commonalities, since the Hadza live in an environment that is more like the one in which we evolved than is that of the !Kung, and the Hadza have been studied with methods and theories that were unavailable when the !Kung were hunting and gathering. There are also differences between the two societies. The !Kung have dogs, so they hunt in groups when in pursuit of game animals that stand and fight the dogs—gemsbok (large antelope), for example. Otherwise the !Kung hunt alone, as the Hadza almost always do. Both use poisoned arrows, but the Hadza have much larger bows with heavy pull weights. Hadza children are weaned at least six months earlier than are !Kung
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children, and interbirth intervals are thus shorter. Hadza children forage for themselves much more. Hadza girls are subjected to partial clitoridectomy at puberty. Marlowe says that the Hadza divorce rate is “close to the same as that of the !Kung,” but this is misleading. As Howell shows, almost all !Kung divorces occur in the first few years of marriage, mainly the first; these are, in effect, trial marriages and are typically childless. Nothing in !Kung culture really matches the common Hadza pattern of men leaving older wives for younger ones, with stepfatherhood resulting if and when the first wife remarries. Cowives exist in both cultures (in about 5 percent of marriages), but among the Hadza the instability of such unions is usually resolved by the abandonment of the older wife, whereas among the !Kung the younger wife departs. Marlowe tests many evolutionary models. He decisively shows that fathers’ provisioning of their wives and genetic children increases the men’s reproductive success by shortening interbirth intervals. Men whose wives are breast-feeding bring home more food. Megan Biesele’s book about !Kung folklore is called Women Like Meat, and Marlowe’s data show that this is true of the Hadza as well, although Hadza men also bring home honey and baobab pods. Grandmothers’ contributions also matter—women are most productive at acquiring food when they are in that age range. Despite the fact that husbands and wives forage separately, proximity of husbands to wives is highly correlated with women’s fecundity (as predicted from their ages), which suggests that mate-guarding as well as provisioning figured in the evolution of pair-bonding. Discussing the reasons for sharing, Marlowe considers nepotism (kin selection), mate provisioning (courtship investment), not-in-kind exchange (meat for honey, say), in-kind delayed reciprocity, costly signaling (to demonstrate foraging ability), and tolerated scrounging. Even with his excellent data, he can’t rule out any of them. Clearly, the impulse of pure generosity explains little; in anonymous games such as the prisoner’s dilemma, the ultimatum game, and the dictator game, the Hadza were among the least generous people ever tested, despite being among the most generous in their culturally sanctioned everyday life. Evolutionary theory is second nature for Marlowe, so much so that his transi-
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tions back and forth between Hadza, chimpanzees and foraging squirrels may seem abrupt to some. But his respect and affection for these brave people is always palpable, and the ease of his nonhuman comparisons simply reflects the depth and breadth of his training under Blurton Jones, as well as the theoretical awareness that now pervades hunter-gatherer studies. Such applications of evolutionary theory and human behavioral ecology by Blurton Jones and others were part of the inspiration for Howell’s book, in which she returns to data she gathered four decades ago, on Harvard Kalahari Research Group expeditions with Lee and DeVore from 1967 to 1969. Life Histories of the Dobe !Kung is an enormous achievement, confirming what can be done with unique archival data in the right hands. It is the newest on a shelf of books that includes Lorna Marshall’s two fine traditional ethnographies of the !Kung; Richard Lee’s classic on their subsistence ecology; Marjorie’s Shostak’s Nisa: The Life and Words of a !Kung Woman; Howell’s earlier book, Demography of the Dobe !Kung (which set the standard for hunter-gatherer demography); and others. So why another book now? Howell writes, “When research methods and theoretical models that were developed in [recent hunter-gatherer] studies are applied to the !Kung, . . . I am impressed by how much we gain in explanatory power.” I am too. Using current lifehistory theory and analytical methods, Howell places adaptation at the center of her account, but on the sound premise that an organism is its life history. She interprets that lifelong adaptive process by mining her demographic data in combination with height, weight and growth data from the same period (1967–1969), some of it analyzed in later collaborations with Patricia Draper. The !Kung, like the Hadza, are small in stature as adults, which lessens the burden of the food quest. On normal Western growth curves, most !Kung infants older than one year fall below the third percentile in height and weight. Howell interprets this (as would most pediatricians) to mean that inadequate caloric intake is pulling down their weight, and in turn their height. However, as she recognizes, teaching children to restrict their food intake may be an adaptation for achieving small adult stature. The body mass index (BMI) of most adults is above 18 (the lower end of the desirable range by Western www.americanscientist.org
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This 18-year-old young man and 17-year-old young woman are in the adolescent stage of life. In !Kung society, adolescence for young women begins with menarche at about age 16 and ends with the birth of the first child at about age 21. Most young women marry shortly after menarche, but conception is usually delayed for several years. Young men marry much later, at a mean age of about 26, so their adolescence is more protracted, giving them the freedom to travel widely. From Life Histories of the Dobe !Kung.
standards), and almost no one has a BMI greater than 25 (the top end of the desirable range). Howell creates a variable she calls BMIDiff—the actual BMI subtracted from the expected (!Kung) BMI for age and sex—a key dependent variable in her analyses. After carefully estimating caloric demands using quantitative data about activities involved in gathering, hunting, leisure, pregnancy and lactation, Howell goes on to assess the caloric productivity of males and females throughout the life cycle. The age curves for adult productivity resemble Marlowe’s for the Hadza, with maximum productivity at roughly 40 to 50 years of age. (The productivity of children is much lower among the !Kung.) The difference between production and consumption of calories among the !Kung is most negative in adolescence and most positive in middle age. The !Kung clearly have a pubertal growth spurt, whereas Marlowe says the adolescent growth spurt in the Hadza is “very minor.” He views this in something like the light in which Howell sees slowed !Kung growth after infancy, regarding it as a way of achieving smaller adult size and lower caloric needs. This brings us to the crux of Howell’s argument about children’s needs. After the second child, household caloric bal-
ance becomes negative, so food must come from somewhere else. Without a partner, neither a mother nor a father could meet the needs of even two children, so Howell, like Marlowe, sees the pair bond as necessary. Howell also sees value in the “grandmother hypothesis”—the theory that menopause is an adaptation allowing women to increase their reproductive fitness by focusing on existing children and grandchildren. Her data, however, don’t strongly support the hypothesis. But just how are the households with more than two children provided for? Here is where BMIDiff, or relative fatness, comes in, as an indicator of investment in offspring. Households do differ significantly in this measure, and we might expect that household caloric balance would predict relative fatness, but there is no significant correlation. As for proximity to kin, multiple regression analysis shows that having a mother, a father, a mother’s mother or a father’s father around predicts relative fatness—but, oddly, having a mother’s father or a father’s mother around predicts thinness. So there is no simple kin-selection explanation of relative fatness. Using different measures than Marlowe, Howell concludes, like him, that genetic relatedness, reciprocity, tolerated scrounging and costly signaling all contribute to pro2011 January–February
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visioning of children. But ultimately, for her, a rule like “feed the thinnest child” affects almost everyone. The fitness benefit to the recipient is an important predictor of altruism under Hamilton’s rule (which states that an altruistic act should be performed when the cost to the actor is less than the benefit to the recipient multiplied by the degree of relatedness between the two individuals). So, given all the factors affecting sharing in !Kung culture, it may be that Howell’s feed-thethinnest-child rule is the most refined that natural selection could come up with. Nevertheless, Marlowe shows that Hadza men do more for their genetic offspring than for their stepchildren. Howell does not resolve this question for the !Kung, but here is the good news: She has put her entire data archive on the Web, with instructions for accessing it, so that any scientist can use the data. If others follow her example, then future cross-cultural comparisons will be more precise. I would be surprised if it turned out that relatedness doesn’t matter, although I expect that it will be shown to
be just one factor predicting sharing in hunter-gatherers. The !Kung today are settled, some successfully, some not. They have made a transition the Hadza have resisted, from living a rough but independent, very ancient lifestyle to being among the poorest people in a poor developing country. It is fortunate that Howell and others were able to study them while they could still teach us so much about human adaptation, and that she has continued the quest in the data archive. Neither the !Kung nor the Hadza nor both societies together can be a sufficient basis for drawing conclusions about the environments of evolutionary adaptedness. Given that some of our ancestors dwelt in tropical forests, groups like the Aka, Efe and Ache are also key models. Before and during the human dispersal out of Africa, it is highly likely that adaptation to shorelines, including shellfish collecting, was important, and for this we turn to models in Australia. In some times and places, rich resources led to higher population densi-
ENVIRONMENT
Fenceline Patrol Lauren Byrnes, Sarah Mele and Daniel Faber SACRIFICE ZONES: The Front Lines of Toxic Chemical Exposure in the United States. Steve Lerner. xvi + 346 pp. The MIT Press, 2010. $29.95.
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teve Lerner, the research director of Commonweal’s Fair Growth Project, always has an important environmental story to tell in his books. His latest, Sacrifice Zones: The Front Lines of Toxic Chemical Exposure in the United States, is a compelling and unnerving account of 12 communities fighting for their right to a clean and healthy environment. The book shows that in towns from Florida to Alaska, residents are discovering that the air they breathe, the water they drink and the homes they live in have been invaded by one or another of a host of dangerous toxins that are associated with a plague of environmentally induced diseases. The industries and U.S. military bases responsible for the pollution appear to be following a clear strategy of sacrificing entire communities as a matter of expediency or to protect bottom lines. To avoid the expense of installing highly effective pollution control systems or disposing of
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toxic substances safely, they are dumping billions of pounds of pollutants in communities where residents have little political or economic power. It follows that those suffering the most are African Americans, Hispanics, working-class whites and indigenous peoples such as the Yupik Eskimos. The “fenceline” communities that Lerner has chosen to investigate are adjacent to some of the most environmentally hazardous sites and facilities in the country. He believes that mixing residential and industrial zones is a dangerous practice and should be avoided. The book demonstrates that companies freely displace, or “externalize,” costs of production onto the public by polluting neighborhoods just outside the factory gates. Yet time after time these companies escape accountability for the damage they cause. The costs may then be absorbed by the state and the larger economy, through
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ties and probably more complex social structures; here Native Americans of the Northwest Coast offer insight. But the Hadza and the !Kung do tell us much about what it means to hunt and gather in warm climates on open plains, especially in Africa, the site of most of human evolution. That the Hadza can still be studied as hunter-gatherers and the !Kung data can still shed new light on this way of life should be cause for celebration. Hunter-gatherers are courageous, resilient, highly skilled, hardworking people who deserve both our admiration and the most thoughtful scientific description and analysis. Both of these excellent books meet that challenge. Melvin Konner, who teaches anthropology and behavioral biology at Emory University, is the author of The Tangled Wing: Biological Constraints on the Human Spirit, second edition, revised and updated (Times Books, 2002), and The Evolution of Childhood: Relationships, Emotion, Mind (Harvard University Press, 2010), which is reviewed on page 68. Website: www.melvinkonner.com
government-funded cleanup operations, emergency-response programs, increased medical and disability costs, and lower commercial and residential property values. But sometimes the government doesn’t want to pay for the cleanup either. Lerner says that agencies and state officials often duck their regulatory responsibilities, sometimes because they find it politically expedient to protect the profits of the polluters. The environmental regulatory system in the United States is proving to be grossly ineffective at addressing such “pollution hot spots” once they are created. Residents of these environmental “sacrifice zones” (a term originally used during the Cold War to designate areas that had been contaminated with radioactive materials from nuclear weapons production) are expected to forgo their fundamental right to a safe and healthy environment. But instead, as Lerner vividly describes, the ecological crises and social injustices they confront have led at least some of them to mobilize into a powerful new movement for environmental justice. Part of what makes Sacrifice Zones such an interesting read is that Lerner gives names and faces to these local heroes. The book is based on hundreds of interviews with the people who are living, working and sometimes dy-
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ing in these communities, and Lerner lets them tell their stories in their own words. Each chapter highlights the perspective of grassroots leaders. Their discussion of their experiences in organizing and mobilizing their communities reminds us that even those in difficult circumstances have the ability to create positive change. Each story offers unique insights into the history of a particular community, the hardships of chemical exposure, or the personal sacrifices that must be made by those fighting corporate polluters and the state. Consistent patterns are found in all of these sacrifice zones: the pollution of less fortunate communities with little means to resist, the failure of industry and government agencies to inform residents of known contamination, the reluctance of regulatory agencies and officials to ensure thorough and quick cleanup of contamination, and the insistence that no action be taken until absolute proof of serious human health effects is available. On reading the first case study in the book, one is likely to think, “What an extraordinary situation!” But then the same political roadblocks show up in one case study after another. Fortunately, Lerner has some major victories to report. He outlines the forces required for bringing about social change, including effective community leaders and grassroots organizing, critical support from dedicated people in the scientific community, legal assistance, organized evidence and a long-term commitment to building the movement. The first two sacrifice zones described are African-American communities in Florida. One is in Ocala, where black soot from the Royal Oak charcoal factory rains down on residents and their homes, and the other is in Pensacola, where excavated sludge containing chemicals such as dioxin, pentachlorophenol, benzene, toluene, dieldrin and asbestos has been piled up into a mound 60 feet high, aptly named “Mount Dioxin.” Both communities consider themselves to be victims of environmental racism, and the evidence suggests that they are right. Early racial segregation in Ocala forced blacks onto unwanted land, and afterward the city invariably found black neighborhoods to be the ideal site for highly polluting facilities. Black Pensacola residents demanded and eventually won relocation to escape environmental health threats, but most were paid very little for their homes or were given inferior replacewww.americanscientist.org
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ment housing; white homeowners in a polluted community in Pennsylvania were given much better treatment. One sad truth that emerges from the book’s case studies is that government and industry often fail to adequately inform residents of contamination risks. Lerner explores the devastation that residents feel when they are informed of serious chemical exposure only after health problems and diseases are already rampant in the community. In the tiny African-American town of Tallevast, also in Florida, townspeople didn’t learn of a severe pollution problem until a resident asked members of a drilling crew why they were boring a hole in her lawn and discovered that they had been hired by the high-tech weapons plant down the street to test the groundwater for toxins. The company that owned the plant, Lockheed Martin, had long known about spills of cancer-causing chemicals into the soil and groundwater and had informed county environmental officials but had decided against informing the townspeople, even though they depended on wells for their drinking water. Kept in the dark for three years, residents were denied their right to make informed choices to protect their health. Similarly, residents of Greenpoint, a Polish-American community in Brooklyn, New York, where 17 to 30 million gallons of oil have leaked into the ground over the past 100 years, were not made aware of a deal between state regulatory officials and oil companies: The companies would gradually remove the oil themselves, and in return the state would not impose fines or a timetable for the cleanup. Residents have been living with contaminated groundwater during what has proved to be a slow and inferior cleanup process. The officials who made the secret deal, Lerner argues, denied citizens important information, thereby failing to protect them from harm. One of the most disturbing patterns Lerner finds in the sacrifice zones is that government agencies (including the Environmental Protection Agency) and local and state officials have often blocked efforts to bring about environmental reform. Citizens rightfully expecting regulatory agencies to be proponents of clean air, water and soil have sometimes been shocked at their unresponsiveness. In Corpus Christi, Texas, state regulatory officials claimed that there were no health concerns when their own air monitoring stations indicated that
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levels of benzene (a carcinogen) were seven times higher than the acceptable standard. In Pensacola, residents were actually harmed by the grossly inadequate and dangerous EPA “cleanup” that created Mount Dioxin. The agency dug up more than 300,000 tons of contaminated soil and placed it in a giant pile in the community under a plastic cover that is now 10 years older than its intended lifespan. Although he recognizes that the EPA had limited funds at its disposal, Lerner argues that their failure to remove the contaminated soils from Pensacola warrants a fuller evaluation of how the agency is handling toxic exposures nationwide. Lerner shows that despite the barriers to enforcing better pollution control, change can occur in these communities when dedicated individuals fight for a cleaner environment. In Corpus Christi, spurred by illnesses in family members and “fed up with what she saw as the do-nothing approach of state regulators,” Suzie Canales founded a group called Citizens for Environmental Jus-
tice. She researched the health effects of environmental pollution in the city for years, pushing for health studies and data on air quality. Unsatisfied with the information provided by regulators, she conducted health surveys and carried out surveillance of refineries. She was questioned by the FBI for “suspicious activity” when she filmed heavy particulate pollution coming off a Citgo facility. Monitoring the air for toxins became much easier for her when an activist working for cleaner air in Port Arthur, Texas, supplied her with an expensive monitor. With the help of environmental organizations, she has begun successfully contesting the air permit applications of refineries. Why does this grandmother have to do the work that regulators should be doing?, Lerner asks. That individuals must invest so much time and effort to protect their right to clean air and water reveals a serious problem within our regulatory system. Lerner’s in-depth exploration of the often-ignored stories of those living
HISTORY
Machines, Minds and Madness Brian Hayes THE CYBERNETIC BRAIN: Sketches of Another Future. Andrew Pickering. x + 526 pp. University of Chicago Press, 2010. $55.
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n 1948 the British neurologist W. Grey Walter began work on a pair of robotic “tortoises”—three-wheeled creatures named Elmer and Elsie that crawled around on the floor seeking light, avoiding obstacles and even engaging in a kind of mating dance. Elmer and Elsie were a big hit at public demonstrations and in a BBC newsreel; Walter also wrote a book about them, as well as two Scientific American articles. And the tortoises had a lasting influence; for example, they inspired the “turtle geometry” that animated computer graphics 30 years later. Walter’s tortoises were an experiment in cybernetics—a word that was still shiny and new then, having been coined by Norbert Wiener just a year earlier. Cybernetics drew heavily on ideas from control theory and the design of servomechanisms, but the aim was to achieve something more than just the stable, self-regulating feedback
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loops of thermostats or float valves. The cyberneticians wanted to build systems with a capacity for boredom and curiosity, fatigue and excitement, learning and forgetting, and maybe even desire and fear. Most of all they wanted to model the brain. The British cybernetics community of the late 1940s and early 1950s was small but enthusiastic. They even had a club, called the Ratio Club, which met in a basement room of the National Hospital for Nervous Diseases in London. The club attracted a diverse membership: Alan Turing was a mathematician and pioneer of computing, I. J. Good a mathematician and statistician, Tommy Gold an astrophysicist. But most of the members came from the neurosciences, psychology or psychiatry (which explains the choice of meeting place). Walter was one of the neuro specialists, an expert in electroencephalography. (He discovered theta
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and dying in America’s most polluted and neglected communities forces us to contemplate the wide disparity between the privileged and the less fortunate. The cost of pollution-control technology is hardly comparable to the toll that contaminants take on residents, some of whom pay with their lives. The thoroughness of Lerner’s research into effective strategies for fighting pollution should prove invaluable for those who struggle for environmental justice. This book offers an inside view of a new form of activism, one that promises to fuse struggles for ecological protection, economic and social justice, and human health into a more transformative environmental politics. Lauren Byrnes and Sara Mele are research assistants with the Northeastern Environmental Justice Research Collaborative in Boston. Daniel Faber is director of the Collaborative and a professor of sociology at Northeastern University. He is the author of several books, including Capitalizing on Environmental Injustice: The Polluter-Industrial Complex in the Age of Globalization (Rowman and Littlefield, 2008).
and delta brain waves.) Another active member, W. Ross Ashby, was the director of a psychiatric hospital in Gloucester. Like Walter, Ashby took up a soldering iron to build cybernetic machines in his spare time. Andrew Pickering’s new book, The Cybernetic Brain, examines the lives and works of six figures in the British cybernetics community, starting with Walter and Ashby. The other four subjects are Gregory Bateson, an anthropologist who turned to psychiatry late in his career; R. D. Laing, a radical psychiatrist (or “antipsychiatrist”); Stafford Beer, who applied cybernetic principles to business management (and also to the national economy of Chile); and finally Gordon Pask, the only one of the bunch who could claim cybernetics as a profession rather than a sideline. In this review I cannot do justice to all six of these stories, so I am going to focus mainly on Walter and Ashby, the pioneers. The British variant of cybernetics emphasized machines that act rather than machines that think; in Pickering’s terms, the distinction is between the performative and the cognitive aspects of the brain. The aim was to model things we do without necessarily being able to articulate how we do them—walking, breathing, maintaining a steady body temperature. Walter’s tortoises offer a
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good illustration, with their goal-directed behavior. They were attracted to light, unless it was too bright, in which case they were repelled by it. They also modified their behavior according to their own internal state, adjusting their brightness threshold when their batteries ran low. (The charging station had a bright lamp.) What the tortoises did not have was any mental representation of the world they moved through, or any semblance of consciousness. This is hardly a surprise: The tortoise brain consisted of two vacuum tubes and a few relays. In spite of this simplicity, Elmer and Elsie were capable of surprising their creator. Each tortoise had a pilot light that turned on when the tortoise was scanning the environment in search of a new light source; then the light winked
Robotic “tortoises” built by W. Grey Walter were icons of the British cybernetics community circa 1950. Here a time-exposure photograph traces the wanderings of one tortoise as it avoids an obstacle and approaches a source of light. In The Cybernetic Brain Andrew Pickering emphasizes that cybernetics was concerned mainly with the “performative” rather than the cognitive aspects of brain function. Nevertheless, Walter’s explanatory labels on the photograph are written in the style of an interior monologue, as if reporting what the tortoise is thinking. www.americanscientist.org
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off as soon as the tortoise locked onto a beacon. Given a mirror, the tortoise would be attracted to its own light, but locking onto the light immediately extinguished it. In front of the mirror, the tortoise began “flickering, twittering and jigging like a clumsy Narcissus.” Ashby’s first foray into cybernetic machinery was a device he called the homeostat. This one didn’t crawl around on the floor. It was a box with lots of knobs and switches, and a pivoting vane on top. Three electrical inputs determined (in a complicated way) a single output current, whose level was indicated by the pivoting vane. One homeostat in isolation didn’t do much; it was designed to hold the output current steady, so that the vane would remain in the middle of its range. But when Ashby wired four homeostats together—with each output becoming an input to another unit—things got interesting, if not chaotic. Each unit tried to maintain its output current near the midpoint, but the balance was upset by fluctuations in the inputs from other units; the resulting excursions in output were then fed back to the other units’ inputs, and so the disturbance continued to circulate through the system. An open question was whether the oscillations would settle down to some stable state, and how long that would take. It’s fair to ask at this point what all these electronic black boxes and cute kitchen-floor robots could possibly have to do with the brain and psychiatry. Ashby thought that the brain might well be an adaptive, self-organizing device something like his network of homeostats. An incoming stimulus would create a disturbance that could rattle around among the units for a while, until the system reached some stable equilibrium, which would constitute the brain’s response to that stimulus. The final configuration would depend on both the stimulus and the system’s internal state—indeed, its entire history. Again, however, there was the question of whether convergence to a stable state was guaranteed, and how long it might take to achieve. Ashby’s estimate was not encouraging. In a fully connected network, with every unit’s output going to every other unit’s input, he found that the settling time would exceed the age of the universe, even for fairly small networks. Thus if the homeostat mechanism is to be salvaged as the basis of a theory of the brain, connectivity must be severely limited.
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Ashby wrote in his diary that his cybernetic experiments were merely an amusement and a hobby, unrelated to his professional responsibilities of caring for psychiatric patients. Pickering refuses to accept this disclaimer; he sees links between the cybernetic hobby and treatments for mental illness, notably electroconvulsive shock and prefrontal lobotomy. Pickering writes: [I]t is hard not to relate Ashby’s later thoughts on the density of connections between homeostat units, and their time to reach equilibrium, with lobotomy. Perhaps the density of neural interconnections can somehow grow so large that individuals can never come into equilibrium with their surroundings, so severing a few connections surgically might enable them to function better. Pickering goes on to remark, “Ashby often failed to drive home these points in print, but that proves very little.” This strikes me as a rather high-handed rhetorical maneuver, insisting on what Ashby must have believed even while acknowledging that he didn’t quite say it. Yet the supposition is not utterly far-fetched; there’s no doubt that Ashby was indeed a proponent of therapeutic interventions such as electroconvulsive shock. The evidence is clearer in the case of Walter. After Elmer and Elsie, Walter built a second generation of tortoises to explore capacities for memory and learning. He found that conflicting stimuli could induce an “experimental neurosis.” Walter wrote: The “instinctive” attraction to a light is abolished and the model can no longer approach its source of nourishment. This state seems remarkably similar to the neurotic behavior produced in human beings by exposure to conflicting influences or inconsistent education. Pickering comments: “[A]fter driving his tortoises mad, Walter cured them.” He proposed three therapies: leaving the machine without stimuli for a while, switching it off and on, and disconnecting some of the circuits. And Walter made the psychiatric analogy overt: Psychiatrists also resort to these stratagems—sleep, shock and surgery. To some people the first seems natural, the second repulsive, and 2011 January–February
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the third abhorrent. . . . [B]ut our simple models would indicate that, insofar as the power to learn implies the danger of breakdown, simplification by direct attack may well and truly arrest the accumulation of self-sustaining antagonism and “raze out the written troubles of the brain.”
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so impressed that he wound up earning a doctoral degree in cybernetics. (There can’t be many of those.) He worked in the theater (creating lighting systems that adapt to the performer) and architecture (designing buildings that adapt to their occupants). He also developed teaching machines and chemical computers. In The Cybernetic Brain Pickering has gathered a trove of stories about a community whose work deserves to be better known. He has done careful and thorough historical research, reading diaries and other unpublished material; in one case he fills in details of a project that had almost sunk from memory— Ashby’s failed attempt to follow up on the homeostat work with a more elaborate system called DAMS. Pickering has also traced the ramifications of cybernetic thought into dozens of surprising (and sometimes dark) corners: the novels of William Burroughs, the music of Brian Eno and that of John Cage, biofeedback, the hallucinogenic drug cul-
ture of the 1960s, the cellular automata of Stephen Wolfram, the architectural patterns of Christopher Alexander, the robots of Rodney Brooks. And he makes acute observations about the social context of cybernetics: For many practitioners it remained a sideline or a kitchentable hobby simply because it never became an established academic discipline or had much institutional support. For the one other professional The stories told here are deeply enpsychiatrist among Pickering’s six gaging. I am grateful to have them. subjects—R. D. Laing—links to cyHowever, I must add that they are told bernetic ideas are tenuous. Pickering and interpreted from an ideological admits that “Laing did not describe viewpoint that I find silly and exasperhimself as a cybernetician,” but Pickating. Pickering’s aim in this book is not ering nonetheless sees something cyjust to revive interest in cybernetics; he bernetic about Laing’s “rumpus room” wants “to challenge the hegemony of approach to psychotherapy, in which modernity.” And modern, in Pickering’s patients and caregivers “were left to vocabulary, is a word that refers not to adjust and adapt to one another, withchronology but to attitude or sensibility. out any prescription how that should Modern science is not just science as it be accomplished.” I suppose there’s happens to be practiced now; it is the an echo here of the homeostat network science of cause and effect, of command settling toward equilibrium, but it’s an and control. The ambition of modawfully faint echo. ern science, he writes, is “the Gregory Bateson also gains achievement of general knowlentry to this group because edge that will enable us to calof his work in psychiatry— culate (or, retrospectively, exone aspect of a highly varied plain) why things in the world career—and he at least had go this way or that.” These are a clear connection with the not words of praise. cybernetic community, as a For Pickering, cybernetics offounder of a conference series fers a nonmodern alternative, a on cybernetics in the 1940s. science that can focus on perHis psychiatric work hinged forming rather than knowon the idea of the double bind, ing, engaging with the world a situation in which none of without trying to control it or the available responses is even, perhaps, to understand satisfactory, as with Walter’s it—rather like Elmer and Elsie neurotic robots. bumbling toward their chargWith Stafford Beer and Goring station. He wants to celedon Pask, cybernetics moves brate the “ontology of unknowwell beyond the mechanistic ability,” resisting the scientist’s models of Walter and Ashby urge to open up the black box, and also leaves behind the precatalogue its parts and draw a occupation with understanddiagram of how it works. The ing the brain and the mind. “sketches of another future” Beer’s early interests were opin Pickering’s subtitle refer to erations research and business his wistful hope that the world management, and he drew up might make room for such a plans for running a steel mill as nonanalytic science. a “cybernetic factory.” He also I am moved to respond to explored biological computing this notion on two levels. First, and at one point thought of realthough the various gadgets cruiting a pond ecosystem as A first sketch of the wiring diagram of the homeostat, another early built by Walter and Ashby the manager of a factory. Then experiment in cybernetics, appeared in the diaries of W. Ross Ashby were more performative than on December 28, 1946. Three inputs (at far left) were combined to he went to Chile during the cognitive, that’s surely not true drive the coils of a milliammeter; the position of the meter’s needle regime of Salvador Allende to (which later became a vane on the outside of the machine) deter- of Walter and Ashby themmanage the nation’s economy mined the voltage applied to the grid of a vacuum tube; the current selves. They wanted not just to on cybernetic principles. through this tube became the output of the device. Interconnecting model brainlike behavior but Pask had an early encounter four such units led to surprisingly complex behavior. From The to understand how the model with Norbert Wiener and was Cybernetic Brain. worked, and ultimately to gain 80
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some insight into how the brain itself works. Stafford Beer later argued that some systems are so complex that true understanding will always elude us. He may have been right, but that does not blunt the desire. As David Hilbert put it: “We must know. We will know.” Second, it is helpful to keep in mind that we usually speak of cybernetics in the past tense, and for good reasons. The framework of ideas erected by Wie-
ner, Walter, Ashby and their followers was not a failure or a dead end, but it is not the armature on which recent students of the brain or of other complex systems choose to build their theories. In computer science these days, the most devastating criticism that can be leveled against an idea is that “it doesn’t scale”—it might work for small problem instances but not for big ones. The methods of Walter and Ashby didn’t scale, as
C L I M AT E
A Fantasy Future David Satterthwaite CLIMATOPOLIS: How Our Cities Will Thrive in the Hotter Future. Matthew E. Kahn. viii + 274 pp. Basic Books, 2010. $26.95.
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limatopolis meets some of the criteria for a good popular nonfiction book: It’s readable, humorous and filled with interesting vignettes. Unfortunately, it fails on the most important criterion: a good knowledge of the topic under discussion. There is little evidence that author Matthew E. Kahn, an economist, has familiarized himself with the literature on climate change and cities. For instance, there are only a few references to papers from the leading climate and urban journals, and no mention is made of any of the assessments of the United Nations Intergovernmental Panel on Climate Change (IPCC). Yet in the IPCC’s Fourth Assessment Report, which was published in 2007, one finds a version of Kahn’s main thesis that is more accurate and more nuanced than the one set forth in the book. The report indicates that many cities have a capacity to adapt to climate change, just as in the past they have adapted to environmental conditions and to frequent changes in resource prices and availabilities. The book goes further. Its subtitle, How Our Cities Will Thrive in the Hotter Future, suggests that cities will not merely adapt, but flourish; however, a subtitle that better reflects the content would be How Some Cities in a Few Prosperous, Large Nations May Benefit from Global Warming in the Next Few Decades. Kahn paints a beguiling picture of a world capable of adapting to climate change, a world in which people are growing wealthier and are making de-
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cisions about where and how to live, using better information than we have now about the challenges that climate change poses. Market forces and human ingenuity (driven mainly by the desire to make money) will support climatechange adaptation, he asserts. As cities experience changing climatic conditions and increased risk of disasters, households will take steps to protect their health, property and quality of life. Adaptation will take place through billions of small choices made by self-interested individuals. They will be helped by water agencies that price water properly and insurance companies that sell policies that price risk appropriately. Lowincome groups may be more at risk, but Kahn is confident that with economic growth they will obtain the resources to allow them to escape risk. Kahn has little use for the idea that government could have any constructive role in these adaptations. Some of the most interesting sections in the book detail the ways in which measures taken by the U.S. government have hindered risk reduction. For example, the government has underpriced water in regions where it is scarce, has helped ensure that insurance coverage is available where risks are high, and has supported reconstruction in devastated areas such as flood plains, despite the high risk that disaster will strike there again. Kahn makes some interesting observations about how various U.S. cities are likely to benefit or suffer from climate change, noting that some will lose population and businesses as their sum-
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they discovered for themselves when they tried to build systems larger than a two-tube tortoise or a four-unit network of homeostats. Their work is no less fascinating for that, but it remains another past, not another future. Brian Hayes is Senior Writer for American Scientist. He is the author most recently of Group Theory in the Bedroom, and Other Mathematical Diversions (Hill and Wang, 2008).
mer temperatures become too hot, while others will make gains as their summer temperatures remain comfortable or their winter temperatures climb. This will shake up the quality-of-life rankings for cities, and people and enterprises will vote with their feet. Kahn thinks that such changes may help reverse the decline of some cities in the Rust Belt, and he suggests that it might be wise to purchase land in Detroit. He also notes that because cold waves increase mortality, higher winter temperatures in some cities will have health benefits. Kahn points out that the residents of a city at risk will not all have the same priorities. For instance, those who live on high ground that is unlikely to flood may see no reason to help fund expensive measures to protect those who live in low-lying areas. And Kahn notes correctly that the cities that have a very large carbon footprint are not the ones that face the most serious risks from climate change. But the book’s interesting observations are outweighed by its problems. It has four major flaws. The first is that Kahn does not recognize that reduction of greenhouse gas emissions needs to be among our highest priorities right now. As the IPCC assessments make clear, any delay in getting an effective global agreement to reduce emissions makes it all the more unlikely that we will be able to avoid dangerous climate change. The book focuses too much on the short term—the likely impacts over the next few decades—and ignores times further in the future, when the effects of climate change may be grave if we take no action now. Kahn, although he acknowledges that large-scale reductions in carbon emissions would be required to lower the concentration of carbon dioxide in the atmosphere, does not appear to understand that well-off households will need to do a lot more than buy an efficient washing machine and air conditioner and the latest Prius. 2011 January–February
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The second problem is that Kahn does not understand the scale and nature of the risk facing most cities (and national economies) in low- and middle-income countries. The book purports to be about cities worldwide; there are passing references to places such as London, Paris, Berlin and Masdar (in Abu Dhabi), and a chapter is devoted to cities in China. But the chief focus is on cities in the United States: A whole chapter is devoted to New York City, and large portions of another chapter deal with Los Angeles; Miami, New Orleans, Detroit, Salt Lake City and others are also discussed. Kahn assumes that lowand middle-income countries will have problems similar to those of wealthy countries, and that cities in the poorest nations will have the same adaptive capacity as prosperous Chinese cities. He admires China, and although he has no good word for governments in wealthy democracies, he thinks that China will have an adaptation edge because of its governance, and because of its skilled population. He vastly overestimates the capacity of cities in low-income and many middle-income nations to adapt. He also greatly overestimates the likelihood that insurance will support needed adaptations; only a very small proportion of urban residents in lowincome nations have disaster insurance. After all, why should insurance companies offer policies to people with limited ability to pay, whose levels of risk are already high and increasing? The third problem is Kahn’s assumption that economic success and market forces will ensure risk reduction. Many nations and cities that will face serious risks from climate change have little economic success, and many of them have carbon emissions per person that are one-tenth or even one-fiftieth of those in cities in the United States. How will their citizens and governments react when they are devastated by climate change that they played little or no role in causing? Also, in many successful cities that are experiencing economic growth, risks from climate change are actually increasing, not decreasing. Most cities in Asia—including Mumbai, a very successful city—have one-third to one-half of their population living in informal settlements, often in very close quarters and in makeshift, insecure housing. These residents are critical to the success of those cities. Yet few city governments extend infrastructure and services to these 82
settlements, even though these amenities are needed for resilience to climate change. Nor do cities manage land use to ensure that sufficient land will be available for housing, so that people need not resort to using sites that are at high risk from floods and storm surges. Kahn approves of providing those living in such settlements with title to their land plots, without understanding how difficult and conflictive this often is (especially for tenants) and without recognizing that the provision of title does not produce the infrastructure needed to protect the inhabitants against extreme weather. The last problem, alluded to earlier, is that Kahn gives little credence to the role of government. He mentions what he refers to as a “fantasy democracy”— one in which government officials anticipate the needs and desires of their constituents, collect taxes, and provide clean water, street safety and roads. He thinks that such democracies don’t exist in the real world, because politicians
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are motivated by self-interest and the desire to get rich. But in fact there are some nations whose governments do accomplish these things. In several Latin American countries, democratic pressures from citizens have changed the constitution, ensured that city governments and mayors are elected, and increased the revenue base of cities. This has opened up opportunities for a new generation of mayors, who are committed to the elements of democracy that Kahn considers fantastical. It is in fact those cities where the urban poor are organized and local government is prepared to work with them that have the greatest capacity to adapt. David Satterthwaite is senior fellow at the International Institute for Environment and Development in London and is the editor of the journal Environment and Urbanization. He is coeditor with Jane Bicknell and David Dodman of the book Adapting Cities to Climate Change: Understanding and Addressing the Development Challenges (Earthscan, 2009).
PHYSICS
Crossing the Danube Peter Pesic DANCE OF THE PHOTONS: From Einstein to Quantum Teleportation. Anton Zeilinger. vi + 305 pp. Farrar, Straus and Giroux, 2010. $26.
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he marvels and paradoxes of quantum theory still exercise an incomparable hold on the contemporary imagination. Even after a century, the “spooky action at a distance” that so disturbed Albert Einstein has not lost its power to perplex and amaze. The enormous number of books on quantum physics bears witness to its enduring fascination; we look to each new account to see what insight or discovery it might convey. In Dance of the Photons, Anton Zeilinger, professor of physics at the University of Vienna and director of the Institute for Quantum Optics and Quantum Information of the Austrian Academy of Arts and Sciences, offers an exciting new perspective. He is one of the leading investigators into the foundations and consequences of quantum theory. His long history of intense involvement in the concrete details of making quantum effects visible and measurable in fundamental experiments is reflected in the book,
setting it apart from many other popularizations. This account also brings a certain Viennese flavor back to the field, showing us experiments that have teleported photons across the Danube and paying respects at Erwin Schrödinger’s tomb in the Austrian Alps. Zeilinger writes with wit and clarity, combining humorous dialogue with an admirably serious and thorough treatment of some of the most challenging and fundamental concepts in modern quantum physics. Dance of the Photons is a wonderful resource for general readers who want to delve more deeply into contemporary quantum experiments and their ramifications. Zeilinger frames his exposition around his group’s experiments on quantum teleportation—the faithful transmittal of a quantum state of a photon from one observer to another, who receives an identical copy of the initial state of a distant photon, although that state was not initially measured. (Such an initial measurement would have re-
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quired that that state then be cloned, And I was really sorry that he inwhich has been proved to be imposcluded almost no bibliography or sible in principle.) Over the years, the notes, not even references to his schematic labels A and B for sender own papers; however popular and receiver have evolved into the and accessible a book may be, it names Alice and Bob, and Zeilinger owes its serious readers guidance chooses those names for the protagoin learning more and going further. nists of his drama: two students in After his account of Bell’s work, Professor Quantinger’s Physics 101 Zeilinger goes on to more recent class, who approach him saying that material, including quantum they want to learn more about quanteleportation and progressively tum physics. He initiates Alice and more intricate forms of quantum Bob into the mysteries of the subject entanglement that lead to quanby giving them the opportunity to tum money, quantum computers carry out a series of explorations and and other intriguing possibilities. laboratory experiments (in which He is careful to distinguish these Alice acts as the sender, needless to amazing ideas from such notions say, and Bob as the receiver). They as Star Trek–style teleportation of begin with the simplest and most people, whose impossibility he fundamental observations of quanta makes clear. I was a little surprised and are gradually led to observe the that he abandons the student “spooky” correlations that Einstein, characters Alice and Bob about a Boris Podolsky and Nathan Rosen hundred pages before the end of made famous. the book; I was quite caught up Zeilinger tells his story with conin their story and ready for more siderable verve and charm; Alice’s of their adventures. Perhaps Zeiland Bob’s questions and perplexities inger felt he should speak in his allow him to air and discuss many own voice when giving an acimportant problems of quantum count of his own experiments. theory. His text is enlivened with That account includes a descripuseful illustrations—many of them tion of his implementation of Ashinformal drawings (some made on er Peres’s proposal for delayedLudwig Boltzmann’s original Vichoice teleportation experiments, ennese blackboard)—which nicely in which crucial decisions by the schematize the issues and help the receiver (who is called Bob, as conreader consider them in visual form. vention dictates, even though the In many ways, Zeilinger achieves a student characters are no longer on tour de force of exposition, considerthe scene) are made long after Aling the subtlety and counterintuitive A gas, initially limited to one side of a container by a ice (the sender) has written down quality of so many quantum con- barrier (top), spreads throughout the whole container her results in final form, yet Bob’s cepts. I very much admired the de- when the barrier is removed (bottom). It is extremely decisions completely change our tail and care he gives to each step improbable that the reverse would ever occur—that all view of Alice’s results. Addressin the argument. Unlike the authors of the atoms of a gas spread throughout a container ing what seems to be the manifest of many popular books, he really (bottom) would happen by chance to move over into contradiction in such proceedings, one side only (top). Einstein noticed that light inside a wants the reader to think about and cavity behaves similarly and conjectured that light, like Zeilinger explains that, although understand the argument or experi- gas, must consist of particles. (This sketch, like many Alice’s facts remain unchanged, ment at hand, rather than merely others in Dance of the Photons, was drawn on Ludwig our interpretation of them may be taking on faith pronouncements Boltzmann’s blackboard.) radically changed by Bob’s obserfrom on high. The book is carefully vational choices. Quantum “realpaced: A certain narrative edge is main- Bell’s celebrated inequality and how it is ity” looks more and more like a litertained, with well-judged pauses over derived. Additional information about ary text: somehow fixed, yet subject to difficult and thought-provoking pas- Bell’s inequality is provided in an ap- interpretation. Spookier and spookier! sages. Zeilinger has a natural interest pendix to the book, nicely solving the Einstein was wrong: Not only does God in the deep philosophical questions that problem of how to give enough detail play dice, he turns out to be an inveteremerge throughout, and he often ad- for the reader who really wants, like Al- ate gambler. dresses them helpfully; one is reminded ice and Bob, to understand what is going of how much thought Schrödinger and on with as little hand-waving or mere Peter Pesic, a physicist, historian and pianist, is Tuthe other founders of quantum theory assertion as possible. So successful is this tor and Musician-in-Residence at St. John’s College, devoted to these questions, which surely appendix that I wish that Zeilinger had Santa Fe. He is the author of several books, includshould continue to engage us. included more such additional explanaing Abel’s Proof: An Essay on the Sources and The climax of this part of Zeilinger’s tory material, whether in appendixes, Meaning of Mathematical Unsolvability (2003) story is a brief, but logically satisfying text boxes or endnotes, for those who and Sky in a Bottle (2005), both published by The MIT Press. and comprehensible, account of John want to understand still more deeply. www.americanscientist.org
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C O N S E R VAT I O N B I O L O G Y
Of Birds and Bureaucracy Jared Farmer SEEKING REFUGE: Birds and Landscapes of the Pacific Flyway. Robert M. Wilson. Foreword by William Cronon. xvi + 245 pp. University of Washington Press, 2010. $35.
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o see wildlife in spectacular abundance, it’s not necessary to visit a wilderness preserve like Yellowstone National Park. Some of the greatest concentrations of birds in North America can be found within the agricultural grid, on tiny refuges sustained by irrigation wastewater from corporate farms. On the Pacific Flyway, one of North America’s four migratory bird corridors, 60 percent of migratory wildfowl winter in California’s Central Valley, one of the most intensively cultivated regions on Earth. This coexistence of avian migration and industrial agriculture is the result of concerted efforts as well as incidental effects. In the early 20th century, irrigation projects disrupted the flyway by destroying wetlands used by migrating birds. These wetlands are “like links in a chain,” writes geographer Robert Wilson, and the flyway is “only as strong as its weakest link.” Wilson’s new book, Seeking Refuge, recounts the history of governmental efforts to repair or refashion particular links. The outcome can hardly be called natural. Today’s refuges, which bear only a passing resemblance to former habitats, were produced rather than preserved. Migratory birds do not behave like spawning fish that insistently return to their home waters. As Wilson says, wildfowl know how and when to migrate, but not precisely where. The ducks and geese of western North America generally move along the corridor between the Pacific Coast and the Rocky Mountains, but the exact routes and destinations vary from species to species, population to population, and year to year. After spending the summer at a breeding ground in Alaska or Canada, a population on the Pacific Flyway travels to a “staging area” such as the mouth of the Bear River at the Great Salt Lake or the marshlands of the Klamath Basin on the CaliforniaOregon border. Following such a sojourn, it continues southward, most likely to central or southern California. The Golden State used to offer a rich va84
riety of aquatic habitats, including the Sacramento River delta, vernal pools, tidal marshes along San Francisco Bay, inland salt marshes at Owens Lake and Mono Lake, and what was once the largest body of water in the American West, Tulare Lake, covering as many as 800 square miles during wet cycles. Not anymore. By the 1930s, 90 percent of California’s wetlands were gone. People turned Bay Area marshes into salt ponds; they converted large parts of the delta into fields and pastures; they drained Tulare Lake and made it a cotton plantation; and they siphoned away the inflow of Owens Lake, creating a dusty playa. Farther south, in Mexico, the delta of the Colorado River progressively dried up as farms and cities appropriated the flow. The government generally facilitated this ecological regime change, but different agencies played contradictory roles. In the 19th century, the federal government gave “swamps” and “overflowed” lands to states. As states drained such property, they could sell it and use the proceeds to drain more land. In 1902, Congress created the U.S. Reclamation Service (which in 1923 was renamed the Bureau of Reclamation)—a whole agency devoted to remaking the deserts and wetlands of the West into irrigated farmlands, with no regard for birds or fish. At the same time, the Bureau of Biological Survey (which after an administrative merger in 1940 was renamed the U.S. Fish and Wildlife Service) was doing its best to preserve avian habitats. Seeking Refuge describes the efforts of the Biological Survey and then the Fish and Wildlife Service to maintain the Pacific Flyway within the new irrigated landscape engineered by the more powerful reclamation agency. Wilson begins with the example of the Klamath Basin. Early in the 20th century, the Reclamation Service spent a lot of money there transforming an incredibly productive wildlife habitat into a moderately productive agricultural district, despite low demand from home-
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steaders. It didn’t matter that President Theodore Roosevelt had established a wildlife refuge there in 1908, because the Klamath Lake Reservation, as it was called, lacked water rights. In 1917, carrying out a plan made years earlier, the Reclamation Service went ahead and cut off the water to Lower Klamath Lake, forcing it to evaporate. Visiting the area in 1935, Biological Survey ornithologist Frederick Lincoln lamented, “It doesn’t even support a good crop of weeds. . . . A jack-rabbit would starve on it.” It was Lincoln who invented the term flyway, after analyzing data from a large-scale avian banding program. By 1930, he and his network of volunteers had banded 740,000 birds and had collected 10,000 bands from dead specimens. Comparing where a bird had been banded with where its body was found allowed ornithologists to hypothesize about the route the bird might have taken between those points. Lincoln named four flyways in North America: the Atlantic, the Mississippi, the Central and the Pacific. The four-region concept grew out of field research, but it also reflected bureaucratic thinking; Lincoln simplified and rationalized a complex natural phenomenon into something comprehensible and mappable. The Bureau of Biological Survey deployed the concept to promote its mission and, as Wilson says, to “compartmentalize space.” Not coincidentally, the Survey reorganized itself into four administrative zones that roughly matched the flyways. Lincoln’s longitudinal study showed that migrating birds took a variety of flight paths within a general flyway. This knowledge encouraged the hope that displaced populations could be rerouted to new refuges. To compensate for the loss of marshes in Oregon, the Biological Survey enlarged wetlands in Utah. At Bear River National Wildlife Refuge, founded in 1928, the Survey borrowed techniques from its nemesis, the Bureau of Reclamation: It reengineered the mouth of the river and created a series of diked ponds that could be drained and filled according to schedule—an artificial disturbance regime. The refuge, which had been plagued by avian botulism, became a “super refuge”; the Survey touted its success in turning a “death trap” into a “supply depot.” Building on this success, the agency redesigned the Pacific Flyway. Using revenue from Duck Stamps (hunting licenses also sold as collectibles), it
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Wildlife photographers William Finley and Herman Bohlman, who made an expedition to the Klamath Basin in 1905, portrayed the basin marshes as an enticing place for bird watching and wildlife adventure. Their reports were instrumental in getting bird protectionists to lobby for the creation of a bird reservation there. This photograph from the expedition shows Finley and Bohlman taking field notes and studying cormorant eggs on the rocky shore of Tule Lake. From Seeking Refuge.
purchased land in the Central Valley, including parcels that had not previously been wetlands. The key site was the Sacramento National Wildlife Refuge, established in 1937. Like a farm, the Sacramento refuge was subject to the water-use regulations of the irrigation district it was part of. Neighboring growers soon complained about “trespassing” waterfowl eating their crops. Because the refuge had junior water rights, the Biological Survey couldn’t afford to alienate the senior water users in the district. To solve the problem of “wayward birds,” the agency turned the Sacramento refuge into a real farm. It grew rice so that ducks and geese would be less tempted to feed elsewhere. When the migratory birds—trespassers www.americanscientist.org
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by nature—continued to ignore boundary lines, wardens used surplus military aircraft for “aerial herding.” They even resorted to antiaircraft searchlights, mortars, grenades and other small explosives to keep birds in segregated spaces. To prevent “duck farms” from spreading insects and weeds to corporate farms, the agency applied herbicides and pesticides, including DDT. By the late 1940s, writes Wilson, “depredation control was becoming the primary purpose of new refuges.” Zoned sanctuaries became mirrors of the very industrial processes and landscapes that had destroyed avian habitats. Now that the Fish and Wildlife Service owned a super refuge (or holding pen, as Wilson calls it) in the Central
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Valley, it turned its attention to the Klamath Basin, the “bottleneck” in the flyway. Unexpected help came from the Bureau of Reclamation, which fixed a flooding problem at its Tule Lake sump by sending excess water to Lower Klamath Lake via a new tunnel. Using this gift of wastewater, in the 1940s the Fish and Wildlife Service carried out a “restoration” program that included a barley operation run by sharecroppers. Ducks and geese—the quarry desired by hunters—thrive on grain, so within a few years, migratory waterfowl had returned in dazzling numbers. Wading birds like herons and egrets, however, have different dietary preferences. Monocultural management of the Klamath refuge privileged the Anatidae family at the expense of nongame birds, not to mention fish, amphibians and mammals. Pacific duck and geese populations increased in the mid 20th century, to general approval. But the consensus over this program began to unravel in the 1970s. Recreational hunters, the chief advocates for large populations of waterfowl, declined in number. A growing constituency, environmentalists, had different ideas about the purpose of wildlife. The politics of water also changed. By the turn of the millennium, many California farmers had sold their water rights to coastal cities, which meant that less irrigation water would find its way to sumps and refuges. Finally, Indian tribes began asserting treaty rights to water and fish. Native Americans made good use of the court system, as did environmentalists, who seized upon the Endangered Species Act as a blunt tool. On the one hand, the Act exponentially increased the authority of the Fish and Wildlife Service. Now it could dictate to the Bureau of Reclamation. On the other hand, species recovery plans could conflict with duck farms. The Endangered Species Act provides no protection for endangered phenomena such as avian migration, only for individual species or for “evolutionarily significant units.” Thus the water needs of endangered fish populations trump the needs of bird reservations. For example, in 2001, the Fish and Wildlife Service directed the Bureau of Reclamation to cut off water to more than 1,200 farms in the Klamath Project in deference to coho salmon runs downstream. No water for farms meant no wastewater for birds. Over the summer, Tule Lake and 2011 January–February
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Lower Klamath Lake shrank. Waterfowl crowded together as farmers lashed out at bureaucrats, environmentalists and Indians. In the wake of multiple lawsuits, Interior Secretary Gale Norton convened a panel of experts to study the crisis. To date, the situation in the Klamath remains acrimonious and litigious. Seeking Refuge does not provide policy recommendations. This concise, understated, well-crafted work allows readers to reach their own conclusions. Despite its narrow focus on the
activities of the Biological Survey and the Fish and Wildlife Service in Utah, Oregon and California, the book has wide relevance. Wilson quietly demolishes the dichotomy of preservation versus development, and challenges the language of environmental restoration. Wildlife is not “out there”; it is all around us, entangled in the places we live and work. Animals and humans share a “hybrid” landscape. Wilson suggests that wildlife habitat cannot truly be restored to its original state.
C O M M U N I C AT I O N
Speaking for the Data Elsa Youngsteadt ESCAPE FROM THE IVORY TOWER: A Guide to Making Your Science Matter. Nancy Baron. xxii + 246 pp. Island Press, 2010. $55 cloth, $27.50 paper. EXPLAINING RESEARCH: How to Reach Key Audiences to Advance Your Work. Dennis Meredith. xvi + 357 pp. Oxford University Press, 2010. $35 paper.
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s a child, Joanie Kleypas was drawn to the television programs of Jacques Cousteau, and they played a role in inspiring her to become a marine ecologist when she grew up. But she never dreamed that she herself would get involved in communicating science to the public. Decades later, however, she was forced into that role when her research uncovered important information. Working at the National Center for Atmospheric Research, she was one of a handful of scientists investigating the effects of rising levels of atmospheric carbon dioxide on ocean acidity. When the first model results came in, showing that ocean acidity would increase greatly, the realization hit her that this would pose a huge threat to marine life. She had to excuse herself from a meeting to go throw up. Kleypas had always shied away from promoting her own work, but the unpleasant revelation that ocean acidification was a very serious problem launched her reluctantly into the public sphere, as she resolved to help policymakers understand and address the matter. Her efforts have paid off: Public awareness of the problem has increased, and federal funds for research have been authorized by the Federal Ocean Acidification Research and Monitoring Act passed by the U.S. Congress in 2009. 86
Kleypas’s story, recounted in Nancy Baron’s Escape from the Ivory Tower, illustrates the resolve required for investigators to leave their comfort zones in the lab, the field and scientific journals in order to deliver bottom-line, jargonfree information to lay audiences. The book summarizes Baron’s decade of experience leading workshops for environmental scientists through the Communication Partnership for Science and the Sea. Her curriculum includes such topics as formulating (and sticking to) a clear message, talking with journalists and policymakers, and promoting a scientific paper. Like her workshops, Baron’s authoritative writing is studded with cameo appearances by researchers who have taken the plunge into the public sphere and have sound advice to offer. Some of America’s best-known science journalists weigh in as well. The book is supplemented by an attractive, user-friendly website (http:// _____ www.escapefromtheivorytower.com/) that provides, among other things, exercises to help scientists decide how much advocacy they’d like to do, videos of scientists offering advice, and links to effective research-lab websites. Unfortunately, although the book was published in August 2010, three months later many of the online resources mentioned in the text still could not be found on the site.
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Like it or not, when we try to save nature we inevitably change it. This is true on the planetary scale and the local scale. By looking to the past, Wilson helps us peer into the future, as we try to imagine the consequences of our efforts and proposals to engineer our way out of the latest environmental crisis. Jared Farmer, a member of the history department at Stony Brook University, is the author of, among other books, Trees in Paradise: A California History (forthcoming from W. W. Norton).
Escape from the Ivory Tower joins a growing throng of recent publications that exhort, even scold, scientists to convey their work more clearly in order to save the world from environmental disaster and scientific illiteracy. These include Chris Mooney and Sheril Kirshenbaum’s Unscientific America, Cornelia Dean’s Am I Making Myself Clear? and Randy Olson’s Don’t Be Such a Scientist. Baron is not a scolder—she presents her guidance with a supportive, can-do attitude. And she defines her readership rather narrowly. “It’s time for the very best scientists to engage,” she writes, and she’s most concerned with highimpact environmental studies that address such problems as the ozone hole and fisheries collapse. For everyone whose work may be merely fascinating, there’s Dennis Meredith’s Explaining Research, an encyclopedic volume of advice based on the author’s 40-year career as a public information officer at research institutions such as Cornell and Duke. Meredith largely dispenses with weighty altruistic reasons for scientists to speak up; instead, he emphasizes how to reach donors, funding agencies, potential students, collaborators and even a researcher’s own family. People do want to listen to scientists, he argues; the American public trusts scientists more than journalists and perceives them as heroes. (In his own assessment of 140 movies, Meredith found that heroic scientists outnumbered villainous ones by 6 to 1.) Having bolstered the reader’s morale, Meredith proceeds to deliver an avalanche of guidance on every facet of explaining research, from giving compelling PowerPoint presentations to advising museum exhibits, shooting video, writing press releases, and talking with the media and with policymakers. On topics that are covered by both Escape from the Ivory Tower and Explaining Re-
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search, Baron and Meredith offer largely concordant advice, but Meredith suggests for his broader audience a wider array of skills and media to pursue. Understandably, he emphasizes the value of working with one’s public information officer and crafting successful press releases—not only in the main text but also in the supplemental booklet “Working With PIOs,” which can be read online at the book’s website (http:// _____ explainingresearch.com/). _________________ Explaining Research includes some astonishing and useful minutiae: When writing for print or the Web, one should revise sentences that contain too many “short” letters such as a, c and n, because it’s easier to read text that combines short letters with tall ones. Readers are reminded to go to the bathroom before participating in Web conferences, and to wear tall socks for television interviews, lest their calves peek out below their pant legs. Unfortunately, preoccupation with so many details sometimes obscures
the big picture. This is particularly evident in Chapter 15, titled “Create E-Newsletters, Wikis, Blogs, Podcasts, Social Networks, and Webinars.” Despite Meredith’s general emphasis on defining and understanding one’s audience, here it’s not entirely obvious for whom and in what context these things should be done—and his examples, such as Science magazine’s respected podcast, do not clarify how an individual researcher might use similar tools. That makes Meredith’s advice no less valid, but it means that parts of his book will be most useful to scientists who already know that they want to pursue a specific means of outreach and just need instructions. Baron and Meredith have each made admirable efforts to incorporate anecdotes, quotes and humor, but their books are undeniably instruction manuals. Most readers won’t cozy up to these volumes in an armchair with hot chocolate, but they’ll be grateful for the investment when they can pull either
GAME THEORY
Honor Among Thieves Cosma Shalizi THE CALCULUS OF SELFISHNESS. Karl Sigmund. x + 173 pp. Princeton University Press, 2010. $35.
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ince the 1970s, a loose community of theoretical biologists, economists, political scientists, mathematicians and philosophers has been using the tools of evolutionary game theory to try to understand how purely selfish agents can come to cooperate, follow norms and even behave altruistically—to understand when honesty is the best policy. Karl Sigmund has been a leading figure in these efforts, and The Calculus of Selfishness is his latest attempt at an introduction to the field. In its exposition, the book focuses on reciprocity between self-interested individuals in certain elementary types of interactions. Game theory (as laid out in chapter 1) models agents interacting with each other, in pairs or in larger groups, with a fixed set of moves available to them. (Sigmund mostly deals with two-player games, but this is just for simplicity.) An agent—Alice, say—has
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a “strategy” that tells her what move to make at each step in the game, in response to another agent’s moves and to the state of the external world (if the model admits that the latter exists). Alice’s coplayer—Bob, say—also has a strategy, and together the two strategies determine the outcome of the game. At its end, Alice and Bob each get a payoff, according to a function that depends on the moves both have made. Their strategies are in equilibrium if neither of them could increase their payoff by changing their moves unilaterally. Basic economics courses lead one to expect that there will be only one equilibrium and that it will be optimal for everyone. The games of relevance to the evolution of cooperation, however, are social dilemmas, where this expectation fails. Sometimes the problem is that the equilibrium is optimal for no one. Imagine that Alice and Bob are
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book off the shelf in times of need. Aspiring journalists and public information officers will also find valuable insights into scientific culture and the way their own work is perceived. Even the more narrowly targeted Escape from the Ivory Tower should be embraced by a broad scientific audience; it’s impossible to predict when, like Kleypas and many others, you may be jolted out of your comfort zone and forced to convince the world that your data matter. Elsa Youngsteadt is a programs manager at Sigma Xi, where she coedits the Science in the News Daily e-newsletter and contributes to Public Radio International’s The World Science podcast. She is also a freelance science writer and holds a Ph.D. in entomology from North Carolina State University.
two bandits, who can either cooperate in robbing villages and caravans, or defect by turning on each other. If they both cooperate, each will take $1,000; if they both defect, neither can steal effectively and they’ll get $0. But suppose that if Alice cooperates and Bob defects by turning on her, he will get $2,000 and she will lose $500—and vice versa. Then regardless of what Alice does, Bob will be better off defecting. So by symmetry, the only way to achieve equilibrium is for both of them to defect—even though they’d both be better off, in purely selfish terms, if they both cooperated. When this type of problem was first posed at the RAND Corporation in the early 1950s, it was framed as prisoners being offered the chance to turn state’s witness, so it is still called the prisoner’s dilemma, and it is the archetype of many cooperation problems. A multiperson version of it is the public goods game, in which something like an open park is shared equally among all participants, no matter how much each of them has contributed to its creation or upkeep. In other social dilemmas, there are many equilibria, some more favorable to one player than to another. If Alice and Bob can agree to cooperate as bandits, how should they 2011 January–February
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split the loot—the extra loot, that is, beyond what they would each get on their own? If Alice can convince Bob that she won’t cooperate unless she gets, say, 75 percent of the gains, it is in Bob’s interest to agree to her demand, since 25 percent extra is better than 0 percent. Thus there is an Alicefavoring equilibrium; but, symmetrically, there is also a Bob-favoring one. However, agreeing to a 50-50 split is not an equilibrium at all. This is called the snowdrift game, after another fable, and is the archetypal depiction of the inevitable struggle over how to divide the gains from cooperation. In evolutionary game theory (introduced in chapter 2), we imagine a population of agents, all with their own strategies, who are randomly paired up to play a given game. The replicator dynamic means that strategies whose players do better than average will increase their share of the population, at the expense of strategies that have worse-than-average results. Whether this works by agents imitating the more successful among them, or by actual natural selection, is not (at this level of abstraction) mathematically relevant. What matters is that the performance of each strategy depends on what other strategies are available in the population and how common they are. The population-level dynamics of strategies are stochastic processes, which in the large-population limit (where Sigmund mostly works) smooth out into differential equations. When are cooperative strategies able to survive or even dominate the population? Chapters 3, 4 and 5 consider mechanisms that can achieve this. Chapter 3 is about direct reciprocity: If Alice and Bob play the same game with each other repeatedly, and each can remember what the other player did earlier, they can pay each other back in kind. In games of the prisoner’s dilemma type, a strategy of cooperating if and only if the other player cooperated last time does not do well against a fixed strategy of noncooperation, but it does do well against another player with the same strategy. It can thus invade a population of noncooperators, although once it becomes dominant, a strategy of unconditional cooperation can invade in turn. These strategies require only very basic sorts of memory; more complex strategies, relying on more sophisticated memories, can be more 88
robust to noise, avoiding costly cycles of retaliation provoked by error and misunderstanding. Chapter 4 extends these ideas to indirect reciprocity, in two forms. In both, Alice’s decision to cooperate with Bob today leads to cooperation tomorrow. In one form, today’s cooperation leads Charlie to cooperate with Alice tomorrow; in the other, it leads Bob to cooperate with Charlie. Chapter 5 looks at norms of fairness and the effects of having a reputation for refusing to violate norms. In the split-the-loot game above, if Alice has established a reputation for refusing to cooperate at all rather than accept unfair divisions, Bob will not bother to offer her a bad deal in the first place. Both indirect reciprocity and reputation require not just memory but also fairly accurate information about what third parties have done— information acquired by perception or communication. Chapter 6 looks in detail at a particular model of the provision of public goods, and at whether voluntary or compulsory participation in providing public goods works better. This chapter is exemplary as an analysis of a model, but the conclusions seem to rest heavily on the assumption that each agent’s reward from the public good goes down in proportion to the population size, which is not true of many public goods, such as roads free of bandits. Up to this point, the book has assumed that players meet randomly, which is of course unrealistic. The final chapter looks briefly at what happens when some internal structure is added to the populations, by spreading them out in space and limiting agents to playing with their immediate neighbors, or by dividing the population into subgroups that mix internally and periodically re-form. This chapter feels less complete than the rest, because it offers just a glimpse of a vast, largely unmapped territory. Sigmund’s mathematical exposition is exemplary. He starts with the presumption that the reader has only rudimentary linear algebra (multiplying vectors by matrices) and some notion of what a differential equation is, and he builds up from there, introducing more advanced concepts and results as needed. He avoids formal proofs and bookkeeping in favor of careful explanations of key points and illustrative calculations.
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As he teaches evolutionary game theory, Sigmund is also demonstrating how to write about applied mathematics. Of course this is not just a mathematical book. That Sigmund calls his two forms of indirect reciprocity vicarious and misguided, rather than, for instance, admiring and grateful, doesn’t change his models, but it probably does shape how readers interpret the models and their properties, and the interpretations are what give the models their interest. (Would anyone study these equations for their own sake?) Since Sigmund, like everyone else in the field, is trying to explain how ethics could arise from selfishness, I suspect that morally charged language is unavoidable, and even desirable, if taken with a grain of salt. These are not matters that mathematics could ever settle, but it is important, and surprising, that mathematics can illuminate them. And Sigmund’s book casts a very bright light. Cosma Shalizi is an assistant professor in the statistics department at Carnegie Mellon University and an external professor at the Santa Fe Institute. He is writing a book on the statistical analysis of complex systems models. His blog, Three-Toed Sloth, can be found at http://bactra.org/weblog/.
Donate Your Back Issues Bridge to Asia, a nonprofit San-Franciscobased organization, wants your American Scientist magazines, academic journals and college-level books. Just pack them tightly in sturdy, manageable-sized boxes and ship them to our warehouses and we'll send them to students and teachers in Asia. Go to the Bridge to Asia Web site at: http://www.bridge.org/books.html and click on “shipping” for more information, including shipping addresses and drop-off arrangements. Shipments sent via the USPS qualify for Media Mail or Library Mail rates. Your out-of-pocket expenses, including packing materials and shipping costs, are tax-deductible together with the value of your books.
Erratum Frederick Mosteller joined the Department of Social Relations at Harvard at the age of 30—not 27, as was mistakenly said to be the case in the review of The Pleasures of Statistics on page 513 of the November–December 2010 issue.
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Golden State Ecology Over a period of 30 years, artistnaturalist Laura Cunningham assisted with biologists’ field studies, researched oral and written histories, and traveled around California with sketch pad and paints to observe declining species and relict habitats. In her new work of historical ecology, A State of Change: Forgotten Landscapes of California (Heyday Books, $50), she reconstructs how some of the state’s landscapes might have appeared in prehistory and shows how they have changed over time. The book will be an illuminating reference for conservationists and urban planners as well as anyone who wants to know California’s landscapes more intimately. And it’s a pleasure to read. Cunningham represents data with hand-drawn diagrams (like the one shown below) that are packed with information and carry a sense of immediacy. The text is clear and thoughtful, and it’s supported by an extensive bibliography. And the book is full of her field sketches, whose expressiveness and economy of line are refreshing. The drawings are often accompanied by lively notes (a sea otter’s movements, she writes, are “fluid & rolling, like a Slinky toy”). At the heart of the book are Cunningham’s oil paintings, imagined landscapes of the distant past. Many of these are paired with present-day photographs. Readers who know California will enjoy seeing familiar views anew, but the paintings will be fascinating, and the contrasts poignant, even to those who have never visited the state. At right, grizzly bears are shown foraging for acorns on a plain that today is
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the parking lot of a shopping center in the Bay Area city of Albany, near the author’s childhood home. Personal and ecological history converge; the result is a loving and discerning portrait that encourages us to imagine how the place might best be treated in the future.
All places deserve to be observed and documented with this kind of wide-ranging attention. Let’s hope that such efforts are supported wherever people like Cunningham are moved to undertake them.—Anna Lena Phillips
2011 January–February
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Sigma Xi
Wilfred Arnold, Professor of Biochemistry, University of Kansas Medical Center
Distinguished Lecturers 2011–2012
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or the 73rd consecutive year, Sigma Xi presents its panel of Distinguished Lecturers as an opportunity for chapters to host visits from outstanding individuals who are at the leading edge of science. These visitors communicate their insights and excitement on a broad range of topics. Each year thousands of Sigma Xi members, students and the public have an opportunity to hear exceptional talks and to ask questions of these experts. The 2011–2012 Distinguished Lecturers are available July 1, 2011–June 30, 2012. Each visitor has consented to a modest honorarium together with full payment of travel costs and subsistence. Local chapters may apply for subsidies to support expenses related to hosting a Distinguished Lecturer. Applications must be submitted online by March 1 for funds to be available the next fiscal year. The Committee on Lectureships is pleased to announce the support of the American Meteorological Society, the National Academy of Engineering, the National Academy of Sciences, the National Cancer Institute and the Society for Risk Analysis. These sponsors nominate a member of their society as a lecturer, and provide funding for additional subsidies. Lecturer biographies, contact information, abstracts of talks and additional program information can be found online under the Lecturership Program link at www.sigmaxi. org. For additional information please send ___ an email to ___________________
[email protected] or call 800-243-6534 x206. The Distinguished Lectureship Program supports the mission of Sigma Xi to promote the health of the research enterprise and the public understanding of science. Willie Pearson, Chair Committee on Distinguished Lectureships
P (Public), G (General), S (Specialized)
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Mark Batzer, Boyd Professor and Mary Lou Applewhite Distinguished Professor, Louisiana State University r5IF*NQBDUPG3FUSPUSBOTQPTPOTPO )VNBO(FOPNF&WPMVUJPO(G,S)r.PCJMF&MFNFOUTBOE1SJNBUF(FOPNJD 7BSJBUJPO(G,S)r.PCJMF&MFNFOUT B/PWFM4PVSDFPG1SJNBUF(FOPNJD 7BSJBUJPO(G,S)
Susan Birren, Professor of Neurobiology, Brandeis University 1MFBTFWJTJUXXXTJHNBYJPSHGPSUJUMFT CZUIFQSFTFOUFSJO/FVSPCJPMPHZ
American Meteorological Society Lecturer Franco Einaudi, NASA Goddard Space Flight Center, Retired 8FBUIFSBOE$MJNBUF*UT4DJFODF *UT "QQMJDBUJPOTBOE*UT$IBMMFOHFT(P,G) r5IF3PMFPG1IZTJDTJO"UNPTQIFSJD 0DFBOBOE&BSUI4DJFODF(G,S)r5IF 3PMFPG4BUFMMJUFTJO4UVEZJOHUIF&BSUIT &OWJSPONFOU(G,S)
S. Douglass Gilman, Associate Professor of Chemistry, Louisiana State University 1SPUFJO"HHSFHBUJPOBOE%JTFBTF*T $IFNJDBM"OBMZTJT6QUPUIF$IBMMFOHF (G,S)r.JDSPGMVJEJDTBOE$IFNJTUSZ 8IZB#JPBOBMZUJDBM$IFNJTU%BCCMFT JO'MVJE%ZOBNJDTBOE.BHOFUJDT(G,S) r4UVEZJOH&O[ZNF*OIJCJUJPOXJUI &MFDUSPQIPSFTJT.JHSBUJOH5ISPVHIUIF $IFNJTUT#VDLFU(G,S) Details available at http://www.sigmaxi.org/programs/lectureships/index.shtml
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Frank E. (Ted) Goebel, Associate Professor of Anthropology, Professorship in First Americans Studies, and Associate Director, Center for the Study of the First Americans, Texas A&M University 5IF*DF"HF%JTQFSTBMPG)VNBOTUPUIF "NFSJDBT%P4UPOFT #POFT BOE(FOFT 5FMMUIF4BNF4UPSZ (P,G)r5IF4FBSDI GPSUIF0SJHJOTPGUIF'JSTU"NFSJDBOT "/FX1SFIJTUPSZPGUIF#FSJOH-BOE #SJEHF(P,G)r)VNBOTBUUIF&OEPGUIF *DF"HF$PQJOHXJUI$MJNBUF$IBOHF $JSDB #$(P,G) Paula Hammond, Bayer Professor of Chemical Engineering, Executive Officer - Department of Chemical Engineering, Massachusetts Institute of Technology /BOPMBZFS"TTFNCMZ"QQSPBDIFTUP #JPNFEJDBM.BUFSJBMTBOEPS&MFDUSPDIFNJDBM%FWJDFT(G,S)r4FMG"TTFNCMZPG 3FTQPOTJWF5IJO'JMNT(G,S)r/BOPTDBMF "TTFNCMZGPS5BSHFUFE%SVHBOE(FOF %FMJWFSZ(G,S)
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Laurie E. Locascio, Chief of the Biochemical Science Division, Chemical Science and Technology Laboratory, National Institute of Standards and Technology #JPMPHJDBM"QQMJDBUJPOTPG.JDSPGMVJEJDT (P,G,S)
Society for Risk Analysis Sigma Xi Lecturer Gregory M. Paoli, President, Decisionalysis Risk Consultants, Inc. Term ends December 31, 2012. Please visit www.sigmaxi.org for a biography, lecture topics and contact information of this speaker
Wesley L. Harris, Professor and Associate Provost, Massachusetts Institute of Technology
Jose-Antonio de la Peña, Full professor Instituto de Matemßticas, Universidad Nacional Autónoma de México
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Gene Helfman, Emeritus Professor, Odum School of Ecology, University of Georgia
William Tad Pfeffer, Professor, Institute of Arctic and Alpine Research and Department of Civil, Environmental, and Architectural Engineering, University of Colorado
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Anthony Johnson, Director of the Center for Advanced Studies in Photonics Research and Professor of Physics and Computer Science & Electrical Engineering, University of Maryland Baltimore County (UMBC) 1IPUPOJDT %JWFSTJUZBOE.FOUPSJOH0WFS :FBSTPG&YQFSJFODFTBOE4USBUFHJFTPO BO"GSJDBO"NFSJDBO1IZTJDJTU(P,G,S) r6MUSBGBTU0QUJDBM$IBSBDUFSJ[BUJPOPG /PWFM/BOPTDBMF.BUFSJBMT(G,S) P (Public), G (General), S (Specialized)
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Howard Pinderhughes, Associate Professor and Chair, Department of Social and Behavioral Sciences, University of California, San Francisco %FBMJOH8JUI%BOHFS)PX*OOFSDJUZ :PVUI$PQF8JUIUIF7JPMFODFUIBU4VSSPVOET5IFN(P,G)r3BDJBM*EFOUJUJFT "UUJUVEFTBOE$POGMJDU"NPOH:PVUI (P,G)r-PWF*T#MJOE3FMBUJPOTIJQ7JPMFODF"NPOH*OOFS$JUZ:PVUI(P,G) Details available at http://www.sigmaxi.org/programs/lectureships/index.shtml
2011
January–February
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William N. Ryerson, President, Population Media Center—Shelburne, Vermont
Lisa H. Weasel, Associate Professor of Biology, Portland State University
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Michael Summers, Professor and Investigator, University of Maryland Baltimore County, and Howard Hughes Medical Institute
National Academy of Engineering Lecturer Donald Winter, Professor of Engineering Practice in the Department of Naval Architecture and Marine Engineering and the Department of Aerospace Engineering at the University of Michigan. Former Secretary of the Navy.
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Sheryl A. Tucker, Associate Dean of the Graduate School and Professor of Chemistry, University of Missouri 5IF1JQFMJOF*HOJUJOH$IJMESFOT*OUFSFTUJO4DJFODF(P,G,S)r'SPN)BWJOHB 1FUUP8PSLJOHXJUIB7FU(P,G,S)r6OEFSTUBOEJOHBOE)BSOFTTJOH.PMFDVMBS $POUBJOFST(G,S)
Statement of ownership, management and circulation (required by 39 U.S.C. 3685). 1. Publication title: American Scientist. 2. Publication number: 0023-240. 3. Filing date: October 1, 2010. 4. Issue frequency: Bimonthly. 5. No. of issues published annually: 6. Annual subscription price: $28. 7. Complete mailing address of known office of publication: P.O. Box 13975, Research Triangle Park, NC 27709-3975. 8. Complete mailing address of headquarters or general business office of publisher: P.O. Box 13975, Research Triangle Park, NC 27709-3975. 9. Full names and complete mailing addresses of publisher, editor, and managing editor: Dr. Jerome Baker, publisher, P.O. Box 13975, Research Triangle Park, NC 27709-3975; David Schoonmaker, editor, P.O. Box 13975, Research Triangle Park, NC 27709-3975; Morgan Ryan, managing editor, P.O. Box 13975, Research Triangle Park, NC 27709-3975. 10. Owner: Sigma Xi, The Scientific Research Society, P.O. Box 13975, Research Triangle Park, NC 27709-3975. 11. Known bondholders, mortgagees, and other security holders owning or holding 1 percent or more of total amount of bonds, mortgages, or other securities: None. 12. The purpose, function, and nonprofit status of this organization and the exempt status for Federal income tax purposes: Has not changed during preceding 12 months. 13. Publication Name:
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P (Public), G (General), S (Specialized) Details available at http://www.sigmaxi.org/programs/lectureships/index.shtml
Application Deadline: March 1, 2011 http://www.sigmaxi.org/programs/lectureships/index.shtml
American Scientist. 14. Issue Date for Circulation Data: Sept/Oct 2010. 15. Extent and nature of circulation: A. Total no. copies: average no. copies each issue during preceding 12 months, 93,178; actual no. copies of single issue published nearest to filing date, 88,844. B. Paid and/or requested circulation: B1. Paid/requested outside-county mail subscriptions stated on Form 3541: average no. copies each issue during preceding 12 months, 48,103; actual no. copies of single issue published nearest to filing date, 42,068. B2. Paid in-county subscriptions: average no. copies each issue during preceding 12 months, 0; actual no. copies of single issue published nearest to filing date, 0. B3. Sales through dealers and carriers, street vendors, counter sales, and other non-USPS paid distribution: average no. copies each issue during preceding 12 months, 13,369; actual no. copies of single issue published nearest to filing date, 14,141. B4. Other classes mailed through the USPS: average no. copies each issue during preceding 12 months, 0; actual no. copies of single issue published nearest to filing date, 0. C. Total paid and/or requested circulation: average no. copies each issue during preceding 12 months, 61,473; actual no. copies of single issue published nearest to filing date, 56,209. D. Free distribution by mail: D1. Outside-county as stated on Form 3541: average no. copies each issue during
preceding 12 months, 526; actual no. copies of single issue published nearest to filing date, 520. D2. Incounty as stated on Form 3541: average no. copies each issue during preceding 12 months, 0; actual no. copies of single issue published nearest to filing date, 0. D3. Other classes mailed through the USPS: average no. copies each issue during preceding 12 months, 0; actual no. copies of single issue published nearest to filing date, 0. E. Free distribution outside the mail: average no. copies each issue during preceding 12 months, 1,191; actual no. copies of single issue published nearest to filing date, 1,162. F. Total free distribution: average no. copies each issue during preceding 12 months, 1,716; actual no. copies of single issue published nearest to filing date, 1,682. G. Total distribution: average no. copies each issue during preceding 12 months, 63,189; actual no. copies of single issue published nearest to filing date, 57,891. H. Copies not distributed: average no. copies each issue during preceding 12 months, 29,989; actual no. copies of single issue published nearest to filing date, 30,953. I. Total: average no. copies each issue during preceding 12 months, 93,178; actual no. copies of single issue published nearest to filing date, 88,844. Percent paid and/or requested circulation: average no. copies each issue during preceding 12 months, 97 percent; actual no. copies of single issue published nearest to filing date, 97 percent.
American Scientist, Volume 99
American Scientist
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January-February 2011 · Volume 20, Number 1
Sullivan Selected President-Elect elly O. Sullivan was
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elected the 75th president of Sigma Xi at the Society’s 2010 Annual Meeting in Raleigh, North Carolina. She will begin her service as president-elect on July 1, 2011. Sullivan is director of institutional partnerships at Pacific Northwest National Laboratory (PNNL). Her research focused on the electronic structure and stability of small molecules and ions of atmospheric and mass spectrometric interest. She received her B.S. from Christian Brothers College and was the first Clare Boothe Luce Graduate Fellow at the University of Notre Dame. She received her Ph.D. in physical chemistry at Texas Tech University in 1994. Sullivan taught at Mankato State University and at Creighton University, where she also directed the Creighton Chemistry Players, a demonstration team that regularly played to standing-room only crowds. In 2001, she left academia to serve as the first director of the Office of Fellowship Programs at PNNL. She transitioned into the role of director of institutional partnerships, identifying the best possible collaborators for PNNL’s research efforts. She contributed to shaping the National Innovation Initiative, which laid the groundwork for the widely-referenced “Rising Above the Gathering Storm” report. She has played an active role in the Government-University-Industry Research Roundtable at the National Academies, leading efforts in STEM education. Sullivan served in several leadership roles for the Omaha Sigma Xi Chapter prior to moving to Washington state. She serves as president of the Tri-Cities Washington Chapter and in a number of capacities at the Society level. “I want people to know what Sigma Xi is and what membership means,” she said. “To achieve this we need to take a hard look at membership criteria and how we elect members. I want Sigma Xi to have the stature it deserves as a one of the few multidisciplinary scientific societies.” She continued, “We need to create and leverage programs that help our members connect and learn from and with each other.” U www.sigmaxi.org
American Scientist
From the President Time for Realistic, Thoughtful Action In recent years, the Society has made many efforts to become or evolve into a more vibrant and effective organization. Our leadership team seems to know what changes are necessary to move Sigma Xi forward. Unfortunately, many of the efforts toward implementation of needed change become stalled—viable, valuable ideas becoming lost at times in endless dialogue. Some of our members claim to have the answers, while others want to point fingers. Still others think of the challenges as strictly an “Executive Committee or President’s” issue or problem. Few take the time to note that while the President is only one individual, the Society’s presidency and leadership involve all of us—every stakeholder and member of Sigma Xi. The good news is that, as an organization, Sigma Xi has the potential, talents and capacity to reinvigorate, re-invent and right itself into a viable, competitive entity. The initial vision for Sigma Xi is still relevant today, and as we celebrate our 125th Anniversary it is time to take charge again. My position is that this is not an impossible goal, nor is it a novel one by any stretch of the imagination—as many organizations have found it necessary to re-invent themselves to remain viable and sustainable. The decline in membership and its impact on financial resources have created a “sense of urgency” for many members—despite years of data and evidence predicting the current state of affairs was inevitable. Bottom line, we did not get to this place overnight, nor will such challenges be surmounted readily or easily (barring appearance of a significantly generous Sigma Xi benefactor). When and where do we begin; where do we go from here? There is a spark: the number of new initiates in FY2010 was greater than in recent years. I viewed the recent symposium at the Annual Meeting as a successful attempt to address issues beyond the society’s governance and business activities; to be a recognized and valued presence among our scientific colleagues; and to significantly limit the drain on revenue normally associated with such an undertaking. The quality of the speakers was outstanding, and they provided a wonderful overview of the interface between science and policy in our ongoing fight to have a safe and secure food supply. With more than 600 registered attendees, it was a great improvement over recent years. Was this good enough? The answer is no; we always should seek ways to improve. We have actively begun planning the meeting for November 2011 with a theme of research ethics. It should be an exciting event that you will want to attend. So what is our mandated new direction or model for Sigma Xi? For this to become clear, we all have a part to play—to recommit and actively contribute to the development of a new vision and direction. Now is the time to be constructive, to act, or to ask how you can help. The Committee on Strategic Planning has invited all members to submit suggestions for action steps to take (see the email address below). Having mandates and ideas are meaningless if we don’t all get involved, contributing our individual and collective talents toward finding solutions to the problem. At the Annual Meeting, a change in the bylaws was approved that will for the first time allow all Sigma Xi members to participate directly in the election of the Society’s leadership by individual ballot. We hope this will give members a greater sense of ownership in your Society. What are you willing to do to get Sigma Xi on a positive, sustainable path? Send me your ideas at
[email protected]! __________ Joseph A. Whittaker 2011 January-February 93
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American Scientist
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Celebrating Sigma Xi’s 125th Anniversary This is the first in a series celebrating Sigma Xi’s 125th anniversary.
as well as at Cornell. Through the 1890s the Society’s membership grew, and by the turn of the century Sigma Xi claimed more than 1,000 members in eight chapters.
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n 1886 at Cornell University, a group of engineering students and junior faculty member Frank Van Vleck began organizing a new scholarly Frank Van Vleck society. The group intended not only to establish an honor society like those already existing in other fields, but also to promote a new, more academically oriented type of engineering education. From the beginning, the founders emphasized that this new scientific honor society would be broad in its outlook, devoted to all of science and engineering, much as Phi Beta Kappa covered the liberal arts. The fledgling organization received its first support from an older member of the Cornell science faculty, geology professor Henry Shaler Williams. Having already tried to establish an honor society for science students, Williams was pleased to merge his interests with those of Sigma Xi’s founders. He became the Society’s chief mentor, serving as the first elected president of the Cornell Chapter and a leader of the growing organization until the turn of the century. Sigma Xi was designed to reward excellence in scientific research and to encourage a sense of companionship and cooperation among scientists in all fields. In selecting a name and motto for the new honor society, the founders chose a combination of Greek letters—Sigma Xi—not being used by any other group. Later, a motto based on these initials was developed to confirm its purpose: Spoudon Xynones, or “Companions in Zealous Research.”
Sigma Xi Chapters 1886-1911 Cornell University Stevens Institute of Technology Rutgers College Rensselaer Polytechnic Institute Union College
In the first decade of the new century, chapters were added at the rate of one to three a year. Many adopted programs that went beyond scientific debate. None, perhaps, matched the importance of those supported by the Stanford and Berkeley chapters after the 1906 San Francisco earthquake. By 1887, Sigma Xi was holding “regular meetings for the discussion of scientific subjects,” and the following year, the group elected five women to full membership, which both promoted the interests of women and made their research more available to the scientific community. Entomologist Anna Botsford Comstock was among the group of women inducted by the Cornell Chapter in 1888. Her 400-page Handbook of Nature Study, published in 1911, is still in print. Also inducted were Susanna Phelps Gage, Hariett Groteclass Marx, Julia Warner Snow and Mary Margaretta Wardall. By that time, chapters had been established at Rensselaer Polytechnic Institute, Union College, Stevens Institute of Technology and Rutgers College,
Anna Botsford Comstock
University of Kansas Yale University University of Minnesota University of Nebraska Ohio State University University of Pennsylvania Brown University Iowa State University
At Stanford, a three-member engineering commission of Sigma Xi members oversaw reconstruction of the campus. The Berkeley Chapter publicized its concerns about public health in the devastated city, where rapidly breeding rats gave rise to cases of bubonic plague. The Berkeley Chapter led an eradication campaign, prodded public officials to action and raised funds. Few chapters have done more for their communities. At its quarter-century anniversary in 1911, Sigma Xi had about 2,000 members in 30 chapters. American Scientist, September-October 1986 UUUUUUUU Sigma Xi, The Scientific Research Society today is known as the international honor society for research scientists and engineers. There are more than 500 Sigma Xi chapters in North America and abroad, at colleges and universities, government laboratories and industrial research centers. Over the years, more than 200 members have received the Nobel Prize. In addition to publishing American Scientist, Sigma Xi awards hundreds of grants annually to promising student researchers and sponsors a variety of programs that support science and engineering. U
Stanford University University of California Columbia University University of Chicago University of Michigan University of Illinois Case School of Applied Science Indiana University
University of Missouri University of Colorado Northwestern University Syracuse University University of Wisconsin University of Washington Worcester Polytechnic Institute Purdue University Washington University
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American Scientist
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Canadian Broadcaster Becomes Honorary Member
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ob McDonald, one of Canada's best-known science journalists, was inducted as an Honorary Life Member of Sigma Xi at the Society's 2010 Annual Meeting. The host of CBC Radio’s award-winning science program Quirks and Quarks, he has been communicating science internationally through television, radio, print and live presentations for more than 30 years.
He is also a regular science commentator on the CBC News Network, science correspondent for CBC TV’s The National and the award-winning host and writer of the children’s series Heads Up! McDonald has also hosted the television mini-series The Greatest Canadian Invention and the seven-part series Water Under Fire. As a print journalist, he has written three science books and contributed to numerous textbooks, newspapers and magazines, including The Globe and Mail, Owl Magazine and many others. His latest book is Measuring the Earth With a Stick, a collection of essays reflecting on his many years as a science journalist. He
wrote the introduction to The Quirks & Quarks Question Book and the Guide to Space: 42 Questions (and Answers) About Life, the Universe and Everything. Beyond his work in media, Bob serves on several boards and is chairman of Geospace, a new environmental center and planetarium in Toronto. McDonald has been honored for his outstanding contributions to the promotion of science in Canada as the recipient of the Michael Smith Award from the Natural Sciences and Engineering Research Council, the Sir Sanford Fleming Medal from the Royal Canadian Institute and the McNeil Medal from The Royal Society of Canada. He also received a 2008 Gemini Award for Best Host in a Pre-School, Children's or Youth Program or Series. McDonald has received six honorary degrees, from the University of Guelph, Carleton University, Laurentian University, McMaster University, University of Calgary and University of Winnipeg. U
Four Members Win Nobel Prizes Three Sigma Xi members shared the 2010 Nobel Prize in Chemistry and a fourth shared the Nobel Prize in Economics. Richard F. Heck (SX 1953) at the University of Delaware, Ei-ichi Negishi (SX 1968) at Purdue University and Akira Suzuki (SX 1964) at Hokkaido
University, Japan, were honored for their development of palladiumcatalyzed cross couplings, a tool used worldwide in commercial production of pharmaceuticals and complex molecules used to make electronics. Peter A. Diamond (SX 1960) at the Massachusetts Inistitute of Technology shared the economics prize for work that helps explain unemployment and job markets.
Over the years, more than 200 Sigma Xi members have received the Nobel Prize. U
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Walters Named Interim Treasurer
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radford B. Walters
was approved by the Board of Directors to be the Society's interim treasurer until the election to be held in November 2011. He is vice president and chief medical officer of RTI International, an independent nonprofit research institution based in Research Triangle Park, North Carolina. RTI scientists provide research and technical expertise to governments and businesses in more than 40 countries. Walters’ primary role is to help shepherd drug candidates developed in RTI’s laboratories into clinical trials for their evaluation as potential human therapeutics. He has been a Sigma Xi member since 1972 and was appointed to the Finance Committee in 2008. As an undergraduate at Harvard, he pursued a joint major in chemistry and physics, graduating summa cum laude in 1973, then traveling to London on a Marshall Scholarship. Walters earned his Ph.D. at University College in 1976, returning to the Harvard-MIT Program in Health Sciences and Technology and completing his M.D. cum laude in 1979. This was followed by an internship in general surgery at Johns Hopkins and residency training in neurological surgery at Massachusetts General Hospital. In 1985, he joined the faculty in the Department of Surgery at the University of North Carolina at Chapel Hill School of Medicine. He left the faculty to complete an M.B.A. at UNC’s Kenan-Flagler Business School and in 2002 joined Academy Funds, a venture capital firm specializing in the commercialization of intellectual property based on university research. In 2005 Walters became an independent life sciences consultant until joining RTI in 2007. He has served on the board of the North Carolina Healthcare Information and Communications Alliance, Inc., a nonprofit consortium dedicated to improving health in North Carolina by accelerating the adoption of information technology and enabling policies. While at Academy Funds, he was appointed a member of the Governor’s Task Force on Nanotechnology and North Carolina’s Economy. U 2011 January-February 95
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The following directors of geographic regions and constituency groups will serve three years beginning July 1, 2011. Research and Doctoral: Robert Zand, University of Michigan Mid-Atlantic: Cristina Gouin-Paul, District of Columbia Northeast: Pamela Kerrigan, College of Mount Saint Vincent The following associate directors will also serve three years beginning July 1, 2011. Multi-Institutional: Andrew Velkey, Tidewater, Virginia Comprehensive Colleges/Universities: Ileana Carpen, Tennessee Technological University Northwest: Prabal Ghosh, Manitoba
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hirty-eight student researchers received awards for their poster presentations at the 2010 Sigma Xi Student Research Conference in Raleigh, North Carolina. Nearly 300 students representing more than 100 academic institutions presented their research at this year's conference. Each year, the Sigma Xi Student Research Conference, held in conjunction with the Society's Annual Meeting, showcases some of the premier student research in the world, and connects senior researchers with students. In addition to the poster competition, the two-day conference featured a variety of networking opportunities. Participants also had a chance to hear talks by leading scientists and engineers, including Sigma Xi award winners. A special award for a student presentation that focused on the theme of Sigma Xi Food Safety and Security symposium was presented to Huiying J. Lu of North Carolina State University. Other student awardwinners were as follows:
Behavioral Sciences Dario Figueroa - University of California, Irvine Seva Khambadkona - The Ohio State
University Biochemistry, Physiology and Immunology Catherine Fick - Oakland University Sarah Lieser - Viterbo University
Cellular and Molecular Biology Nicole Anayannis - SUNY Purchase Myurajan Rubaharan - George Mason University Alvin Shi - Duke University Jennifer Yonan - University of California, Irvine
Chemistry Anthony Prosser - University of Kansas
Ecology & Evolutionary Biology Kristina Bonaparte - University of California,
Irvine Engineering An Truong - North Carolina State University
Graduate and Doctoral Candidate Division
Environmental and Geo-Sciences
Behavioral Sciences
Interdisciplinary Research
John Hernandez and Katie Adams - Texas
Lauren Marston - North Carolina State University
A&M University - Corpus Christi
Emma Babb - Duke University Gino Graziano - Santa Barbara City College
Biochemistry, Physiology and Immunology
Math and Computer Science
North Central (to fill term ending June 30, 2012): Gus Buchtel, University of Michigan
Samantha Furr - University of North
Top Electing Chapters The following Sigma Xi chapters were recognized at the 2010 Annual Meeting for initiating the most new members in 2009-2010: Brown University, Claremont Colleges, Swarthmore College, Massachusetts Institute of Technology, Washington University, Smith College, Amherst College, Williams College, Carleton College, Texas A&M University, Mount Holyoke College, Wellesley College, University of Missouri, Lafayette College and Denison University. U
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Undergraduate Division
Southeast (to fill term ending June 30, 2011): Julio Turrens, University of South Alabama
Southwest: Bertis B. Little, Tarleton State University U
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Thirty-Eight Students Receive Medals at Sigma Xi Conference
Society Directors Elected uring the 2010 Sigma Xi Annual Meeting and International Research Conference in Raleigh, North Carolina, chapter delegates elected members to the Society’s Board of Directors.
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Christine Sawyer - Santa Barbara City College
Carolina at Charlotte
Physics and Astronomy
Cellular & Molecular Biology
Alex Garner - University of Florida
Matti Asuma - University of Wisconsin -
High School Division
Madison Huiying Lu - North Carolina State University
Interdisciplinary Research including Behavioral Sciences
Chemistry
Givi Basishvilli - Harlem Children Society
Jessica Bongiovanni - University of North
Biochemistry, Physiology & Immunology
Carolina at Charlotte Ecology & Evolutionary Biology
Angela Zhang - North Carolina School of
Science and Mathematics
Luanna Prevost - University of Georgia
Kimberly Clark - Josephine Dobbs Clement
Engineering
Early College High School
Eric Forrest - Massachusetts Institute of
Cellular & Molecular Biology
Technology Andrew Loebl - North Carolina State
William Su - North Carolina School of Science and Mathematics
University
Chemistry
Environmental and Geo-Sciences Kelly Smith - University of North Carolina at
Taylor Adair - William G. Enloe High School Joseph Moo-Young and Nick Liu - North
Charlotte
Carolina School of Science and Mathematics
Interdisciplinary Research
Ecology & Evolutionary Biology and Environmental Science
Vikrant Dutta - North Carolina State University Seth Ebersviller - University of North Carolina
at Chapel Hill
Yun Tang - North Carolina School of Science and Mathematics
Math, Computer Science, Physics and Astronomy
Math, Computer Science, Physics, Astronomy and Engineering
Farzad Sadjadi - University of Minnesota
Melissa Chan - William G. Enloe High School
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American Scientist
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F-R-E-E. Stauer comes to the rescue! $295 necklace of genuine cultured pearls…FREE!
Y
ou read that right. If you’d like the Stauer genuine 18" cultured pearl necklace absolutely FREE, all you need to do is call us today or log on to the website www.stauer.com. There is no catch. If you’re wondering exactly how we can afford to do this... read on. Despite tough economic times, Stauer has had a very good year. It’s time for us to give back. That’s why we’re offering this stunning, 18" strand of genuine cultured white pearls for FREE (you only pay the basic shipping and processing). This is a classically beautiful necklace of luminous, smooth cultured pearls that fastens with a .925 sterling silver clasp ($295 suggested retail price). It is the necklace that never goes out of style. In a world where some cultured pearl necklaces can cost thousands, shop around and I doubt that you will see any jewelry offer this compelling! Why would we do this? Our real goal is to build a long term client relationship with you. We are sure that most of you will become loyal Stauer clients in the years to come, but for now, in this lousy economy, we will give you these pearls to help with your future gift giving ideas. We did find a magnificent cache of cultured pearls at the best price that I have ever seen. Our pearl dealer was stuck. A large luxury department store in financial trouble cancelled a large order
at the last minute so we grabbed all of them. He sold us an enormous cache of his roundest, whitest, most iridescent cultured 5 ½–6mm pearls for only pennies on the dollar. But let me get to the point: his loss is your gain. Many of you may be wondering about your next gift for someone special. In the past, Stauer has made gift giving easier with the absolute lowest prices on fine jewelry and luxury goods. This year, we’ve really come to the rescue.
For the next few days, I’m not offering this cultured pearl necklace at $1,200. I’m not selling it for $300. That’s because I don't want to SELL you these pearls at all... I want to GIVE them to you. This cultured freshwater pearl necklace is yours FREE. You pay nothing except basic shipping and processing costs of $24.95,, the normal shipping fee for a $200–$300 necklace. It’s okay to be skeptical. But the truth is that Stauer doesn’t make money by selling one piece of jewelry to you on a single occasion. We stay in business by serving our long term clients. And as soon as you get a closer look at the exclusive selection, you’re not going to want to buy your jewelry anywhere else. Stauer is a high end jeweler that still understands value. As a matter of
fact, our average client spends more with us than at Tiffany’s, but we still know something about affordability. We believe Stauer was the largest buyer of carat weight emeralds in the world last year and this year we are on track to be the largest buyer of carat weight sapphires, so we know about volume buying discounts. We were only able to get so many pearls at this price. This offer is very Ask about our limited to one per satin and velvet travel case. shipping address. Please don’t wait. JEWELRY SPECS: - Genuine 5 ½-6mm white cultured pearls - 18" strand - Sterling silver clasp
Cultured Pearl Necklace (18" strand) Your Cost—FREE — pay shipping & processing only. Call now to take advantage of this extremely limited offer.
1-800-806-1654 Promotional Code FWP442-10
Please mention this code when you call.
Stauer
14101 Southcross Drive W.,
® Dept. FWP442-10
Burnsville, Minnesota 55337
www.stauer.com
Smar t Luxuries—Surprising Prices
American Scientist
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American Scientist
Four Billion Years in the Making ... Continents move. Glacial cycles come and go. Mountains form and erode. We live on a planet constantly in motion—except it’s usually extremely slow motion. In the 48 exciting lectures of How the Earth Works, speed up the action and witness the entire history of our planet unfold in spectacular detail, learning what the Earth is made of, where it came from, and, above all, how it works. This unforgettable course is an astonishing journey through time and space. From the big bang to small geological forces, you explore the fascinating processes involved in our planet’s daily life. You also discover insights into volcanoes, the rock cycle, tsunamis, the ocean VHDÀRRU DQG RWKHU IDVFLQDWLQJ QDWXUDO SKHQRPHQD$Q LQWHUQDWLRQDO innovator in seismology and geophysical education, award-winning Professor Michael E. Wysession provides you with a breathtaking, comprehensive picture of our remarkable home. This course is one of The Great Courses , a noncredit, recorded college lecture series from The Teaching Company $ZDUG winning professors of a wide array of subjects in the sciences and the liberal arts have made more than 300 college-level courses that are available now on our website. ®
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Geology’s Impact on History Geologic History—Dating the Earth Earth’s Structure—Journey to the Center Earth’s Heat—Conduction and Convection 5. The Basics of Plate Tectonics 6. Making Matter—The Big Bang and Big Bangs 7. Creating Earth—Recipe for a Planet 8. The Rock Cycle—Matter in Motion 9. Minerals—The Building Blocks of Rocks 10. Magma—The Building Mush of Rocks 11. Crystallization—The Rock Cycle Starts 12. Volcanoes—Lava and Ash 13. Folding—Bending Blocks, Flowing Rocks 14. Earthquakes—Examining Earth’s Faults 15. Plate Tectonics—Why Continents Move 16. The Ocean Seafloor—Unseen Lands 17. Rifts and Ridges—The Creation of Plates 18. Transform Faults—Tears of a Crust 19. Subduction Zones—Recycling Oceans 20. Continents Collide and Mountains Are Made 21. Intraplate Volcanoes—Finding the Hot Spots 22. Destruction from Volcanoes and Earthquakes
23. Predicting Natural Disasters 24. Anatomy of a Volcano—Mount St. Helens 25. Anatomy of an Earthquake—Sumatra 26. History of Plate Motions—Where and Why 27. Assembling North America 28. The Sun-Driven Hydrologic Cycle 29. Water on Earth—The Blue Planet 30. Earth’s Atmosphere—Air and Weather 31. Erosion—Weathering and Land Removal 32. Jungles and Deserts—Feast or Famine 33. Mass Wasting—Rocks Fall Downhill 34. Streams—Shaping the Land 35. Groundwater—The Invisible Reservoir 36. Shorelines—Factories of Sedimentary Rocks 37. Glaciers—The Power of Ice 38. Planetary Wobbles and the Last Ice Age 39. Long-Term Climate Change 40. Short-Term Climate Change 41. Climate Change and Human History 42. Plate Tectonics and Natural Resources 43. Nonrenewable Energy Sources 44. Renewable Energy Sources 45. Humans—Dominating Geologic Change 46. History of Life—Complexity and Diversity 47. The Solar System—Earth’s Neighborhood 48. The Lonely Planet—Fermi’s Paradox
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