Scientific American April 2009 ■ Volume 300 Number 4

Virus Watch: Preventing the Next Pandemic

Solving the Mystery of the VANISHING BEES page 24 April 2009 $5.99 U.S. U.K. £4.10 www.SciAm.com DARK ENERGY Does it really exist? Or does Earth occupy a very unusual place in the universe?

Color Vision Our Eyes Reflect Primate Evolution Green Lasers The Next Innovation in Chip-Based Beams Soldiers’ Stress What Doctors Get Wrong about PTSD

features ■

Scientific American April 2009 ■ Volume 300 Number 4

COSMOLOGY Does Dark Energy 32 Really Exist? By Timothy Clifton and Pedro G. Ferreira The observations that led astronomers to deduce the existence of dark energy could have another explanation: our galaxy may lie at the center of a giant cosmic void.

LIFE SCIENCE 24 Saving the Honeybee By Diana Cox-Foster and 24 Dennis vanEngelsdorp The mysterious ailment called colony collapse disorder has wiped out large numbers of the bees that pollinate our crops. The causes turn out to be surprisingly complex, but solutions are emerging.

evolution 40 The Evolution of Primate Color Vision 40 48 By Gerald H. Jacobs and Jeremy Nathans Analyses of primate visual pigments show that our color vision evolved in an unusual way and that the brain is more adaptable than generally thought.

PSYCHOLOGY 48 The Post-Traumatic Stress Trap By David Dobbs A growing number of experts assert that over On The Cover diagnosis of post-traumatic stress disorder may The observable universe, with the Milky Way galaxy compound the suffering of soldiers who are actually near its center, might be just one relatively empty afflicted with depression, brain trauma or other part of a larger, unevenly expanding cosmos. problems or who are simply taking time to adjust. Image by Kenn Brown, Mondolithic Studios.

MATERIALS SCIENCE 54 The Dawn of Miniature 54 Green Lasers By Shuji Nakamura and Michael Riordan Semiconductors can generate laser light in all colors except one. But new techniques for growing laser diodes could soon make brilliant full-spectrum displays a reality.

PUBLIC HEALTH 60 Preventing the Next Pandemic 60 By Nathan Wolfe An international network for monitoring the flow of viruses from animals to humans might help scientists head off global epidemics.

go to .com Slide Show: Worms ’N Us  8 In-Depth Report Meet the charming, slinky creatures that turn The Science of Food Learn about test-tube pork, the myth of the heirloom to- your innards into their home sweet home. mato and the quest to take bug by-products out of candy. More at www.SciAm.com/apr2009 8 News Alien Census: Can We Estimate How Much Life Is Out There in Space? A recent study proposes a computer model to tabulate the extent of extraterrestrial intelligence. ition, Ed

th 8 60-Second Psych Podcast FIF , 2005 Near Misses Motivate Gamblers , LLC

s Great news for the house: parts of gamblers’ brains that get excited by winning light up at near wins, too. uction d Pro

s 8 Ask the Experts PARASITICDISEASES,

ree Can a Person Be Scared to Death? y of y s le T Medical science and the criminal courts agree the an-

ourte — C swer is yes as in the case of a fugitive who induced a fatal heart attack in a 79-year-old woman. Scharf;d

ommier et al., App 8 60-Second Extinction sp e

. d Countdown Blog h by Davi by h p After 1,000 Years, the Milu Returns to the Wild on d s

ick Few species have come as close to extinction and

Photogra by d survived as the Chinese milu has.

Scientific A merican (ISSN 0036 -8733), published monthly by Scientific A merican, Inc., 415 Madison Avenue, New York, N.Y. 10017-1111. Copyright © 2009 by Scientific American, Inc. All rights reserved. No part of this issue may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying and recording for public or private use, or by any information storage or retrieval system, without the prior written permission of the publisher. Periodicals postage paid at New York, N.Y., and at additional mailing offices. Canada Post International Publications Mail (Canadian Distribution) Sales Agreement No. 40012504. Canadian BN No. 127387652RT; QST No. Q1015332537. Publication Mail Agreement #40012504. Return undeliverable mail to Scientific A merican, P.O. Box 819, Stn Main, Markham, ON L3P 8A2. Subscription rates: one year $34.97, Canada $49 USD, International $55 USD. Postmaster: Send address changes to Scientific American, Box 3187, Harlan, Iowa 51537. Reprints available: write Reprint Department, Scientific American, Inc., 415 Madison Avenue, New York, N.Y. 10017-1111; (212) 451-8877; fax: (212) 355-0408. Subscription inquiries: U.S. and Canada (800) 333-1199; other (515) 248-7684. Send e-mail to [email protected] Printed in U.S.A.

4 From the Editor 5 Letters 7 8 7 50, 100 and 150 Years Ago 8 Updates

9 Ne w s Sc an ■ ■ Synthetic life oozes closer. ■ ■ Microfluidics scrutinizes cancer cells. ■ ■ Smarter algorithms help to find new particles. 9 ■ ■ A novel theory on seasickness. ■ ■ Selfishness that boosts altruism. ■ ■ Southern Pacific rattlesnake vs. humans. ■ ■ Bus-size snake (fossilized, thankfully). ■ ■ Data Points: The disappearance of trees.

Op inion 1 9 SciAm Perspectives Healthy growth for U.S. farms. 2 0 Sustainable Developments By Jeffrey D. Sachs Rather than arguing about the value of taxes or spending, economic planners need to take 6 6 Reviews a systematic long view. Human mysteries. Mathematical mysticism. Resistance of the real. 2 2 Skeptic By Michael Shermer 68 Ask the Experts Are successful people primarily the beneficiaries If galaxies are all moving apart at ever increasing of luck, timing and cultural legacy? speed, how can they collide? Why do we feel so 2 3 Anti Gravity hot when our By Steve Mirsky surroundings Obscene wastes are at body of science funding. temperature?

19 22 68

Nothing Special We’re an ordinary species on an ordinary planet. Or are we?

“You are not special,” the char- mological geometry. It avoids invoking acter Tyler Durden warns his dark energy as an ad hoc cause but at the followers in the movie Fight price of throwing out the Copernican prin- Club and in the namesake ciple: roughly speaking, it puts Earth, or at novel by Chuck Palahniuk. least our galaxy, back at the center of the “You are not a beautiful or unique snow- observable universe. Timothy Clifton and flake. You’re the same decaying organic Pedro G. Ferreira explore that idea in matter as everything else.” Durden’s harsh “Does Dark Energy Really Exist?” begin- but not inaccurate assessment lays the ning on page 32. Among Our foundation for that story’s subsequent tu- Even if the Copernican principle’s appli- Contributors mult. The same idea under the name the cation to cosmology is subject to amend- “Copernican principle” also happens to ment, its application to other areas of sci- Timothy Clifton have been a linchpin of science for the past ence, notably biology, remains robustly is a cosmologist and relativity theorist at the University four centuries. (The first rule of the Coper- well supported. (The second rule of the Co- of Oxford and wrote the nican principle is, Do not talk about the pernican principle is, Do not talk about the popular astronomy book The State of the Universe. Copernican principle, but....) Copernican principle....) It can nonethe- In 1543 Copernicus gave the establish- less offend humans’ self-importance: wit- Diana Cox-Foster ment of his day a bloody nose by propos- ness creationists’ ongoing push-back studies host-pathogen interactions among insects, ing that the best explanation for the ob- against the evolutionary concept that peo- including honeybees, as a served motions of the stars and planets ple are simply another type of animal. professor of entomology at Pennsylvania State University. was to picture the sun, not Earth, as the And yet biological evidence of our kin- center of known space. He had the pru- ship with other creatures is everywhere we David Dobbs dent good sense to promptly die. Sixty look. Gerald H. Jacobs and Jeremy Na- is a contributing editor of Scientific American Mind as well as author of years later the Vatican kayoed two as- thans reveal the literal truth of that state- three books and articles for the tronomers who forced the point more ag- ment in “The Evolution of Primate Color New York Times Magazine, Audubon and other publications. gressively: it burned Giordano Bruno at Vision” (page 40). Humans, apes and mon- the stake and caged Galileo until he threw keys see a range of colors that other mam- Shuji Nakamura in the towel (while angling for a rematch mals do not; more tellingly, the genetic and pioneered the development with a mumbled “Eppur si muove”). Nev- biomolecular details of how humans and of blue diode lasers. He directs the Solid-State Lighting and ertheless, the facts were on the scientists’ Old World primates (to whom we are most Energy Center at the University side. Astronomers now develop their the- closely related) see color are different even of California, Santa Barbara. ories mindful that Earth most likely oc- from those of their New World cousins. Michael Riordan cupies an ordinary, unprivileged place in Our relatedness to other animals also is co-author, with Lillian the cosmos. leaves us with some common vulnerabili- Hoddeson, of Crystal Fire: So 11 years ago, when astronomers sud- ties. When an evolving viral disease hops a The Invention of the Transistor and the Birth of denly realized that the universe was not species barrier, it can sometimes cause hor- the Information Age. merely expanding but accelerating in its ex- rific infections. Virologist Nathan Wolfe Dennis vanEngelsdorp pansion, most of them concluded that some proposes in “Preventing the Next Pandem- kept bees as an undergraduate otherwise undetectable antigravity force, ic” (page 60) that health authorities moni- at the University of Guelph and a “dark energy,” was shoving apart galax- tor the status of animal diseases on the now serves as acting state apiarist for the Commonwealth ies. An alternative possibility, however, can verge of leaping to humans. That fight is of Pennsylvania. explain the observations as a fluke of cos- one we do not want to lose. ) Nathan Wolfe

directs the Global Viral John Rennie Rennie Forecasting Initiative and is editor in chief

a visiting professor of arsen ( human biology at

Stanford University. flynn L

® Financial Crisis ■ Car Tech ■ Earthrise Established 1845

EDITOR IN CHIEF: John Rennie EXECUTIVE EDITOR: Mariette DiChristina MANAGING EDITOR: Ricki L. Rusting CHIEF NEWS EDITOR: Philip M. Yam SEnIor writeR: Gary Stix “The SEC decision the editors cite EDITORS: Peter Brown, Davide Castelvecchi, Graham P. Collins, Mark Fischetti, was made by politicians and bank Steve Mirsky, Michael Moyer, George Musser, Christine Soares, Kate Wong management, none of whom CONTRIBUTING EDITORS: Mark Alpert, Steven Ashley, Stuart F. Brown, W. Wayt Gibbs, was a practicing quant.” Marguerite Holloway, Christie Nicholson, —Gerald A. Hanweck, Jr. NEW YORK CITY Michelle Press, Michael Shermer, Sarah Simpson

managing editor, ONLINE: Ivan Oransky December 2008 news editor, ONLINE: Lisa Stein ASSOCIATE EDITORS, ONLINE: David Biello, Larry Greenemeier ■■ Don’t Shoot the Prognosticator ■■ Driving Out of Control news Reporters, ONLINE: Coco Ballantyne, Jordan Lite, John Matson “After the Crash” [Perspectives] places part In “Driving toward Crashless Cars,” Ste- ART DIRECTOR, online: Ryan Reid of the blame for the current financial crisis ven Ashley discusses next-generation auto- on the software models created by the phys- motive safety technology that takes various ART DIRECTOR: Edward Bell ics and math specialists—whom Wall Street measures of control from the driver, includ- senior associate ART DIRECTOR: Mark Clemens ASSISTANT ART DIRECTOR: Johnny Johnson refers to as quants—to police investment ing robotic cars capable of riding in close ASSISTANT ART DIRECTOR: Jen Christiansen banks after the Securities and Exchange formation without any driver intervention. PHOTOGRAPHY EDITOR: Monica Bradley PRODUCTION EDITOR: Richard Hunt Commission (SEC) lifted a rule requiring Apart from safety concerns, society has yet them to maintain debt ceilings and federal to utilize such technology to make the flow COPY DIRECTOR: Maria-Christina Keller reserves in 2004. Pointing fingers at the of traffic more fuel-efficient, a pressing COPY CHief: Daniel C. Schlenoff COPY AND RESEARCH: Michael Battaglia, quants for their imperfect financial models need in this era. In particular, the infrared Aaron Shattuck, Rachel Dvoskin, Aaron Fagan, is like blaming meteorologists for imper- laser and microwave radar in speed-atten- Michelle Wright, Ann Chin fect models of climate change or immunol- uating collision avoidance systems should

Editorial Administrator: Avonelle Wing ogists for their imperfect models of AIDS. be installed on all new cars to simultane- SENIOR SECRETARY: Maya Harty Such scientists overwhelmingly understand ously slow down and space out vehicles. that their models are imperfect and are Networked-highway and GPS technology ASSOCIATE PUBLISHER, PRODUCTION: constantly trying to better them. that reads digital signage and computes William Sherman MANUFACTURING MANAGER: Janet Cermak The crisis was not caused by models run variable speed limits to slow vehicles ahead ADVERTISING PRODUCTION MANAGER: Carl Cherebin amok. The SEC decision the editors cite was of freeway congestion is another fuel-sav- PREPRESS AND QUALITY MANAGER: Silvia De Santis PRODUCTION MANAGER: Christina Hippeli made by politicians and bank manage- ing and safety-enhancing innovation that C USTOM PUBLISHING MANAGER: ment, none of whom was a practicing could be deployed quickly. Madelyn Keyes-Milch quant. The banks disregarded their risk Gregory Wright Board of Advisers management groups, and ambitious politi- Sherman Oaks, Calif. cians and cozy relationships between lend- Rita R. Colwell Distinguished Professor, University of Maryland ers, servicers and government spurred on Reading Ashley’s article makes me want College Park and Johns Hopkins Bloomberg School lending. Many quant models showed that to keep my Saturn on the road for a long, of Public Health the housing bubble was growing out of long time. The idea of having to compete danny hillis Co-chairman, Applied Minds control as far back as 2005. Up and down with a computer for control of a car sounds Vinod Khosla the chain of leadership—from Congress to dangerous. At the very least, the “preset Founder, Khosla Ventures the Bush administration to bank manage- distance” to be maintained by a forward- M. Granger Morgan ment to mortgage lenders and brokers to collision warning system needs to be user- Professor and Head of Engineering and Public homebuyers—the problem was ignored. programmable. In Detroit rush-hour traf- Policy, Carnegie Mellon University The editors acknowledge other causes of fic, if you let your following distance open Lisa Randall Professor of Physics, Harvard University the crisis but fail to accept that the govern- up to three quarters of a car length, some- George M. Whitesides ment owns the lion’s share of the blame. one will pull into it. Professor of Chemistry, Harvard University Gerald A. Hanweck, Jr. Lee Helms New York City Hazel Park, Mich. www.SciAm.com © 2009 SCIENTIFIC AMERICAN, INC. SCIENTIFIC AMERICAN 5 letterS ■

■■ Film Stars? As examples, he ascribes various irratio- The “Earthrise” photograph taken of our nal beliefs to “UFOlogists,” “religionists” ® planet from the moon during the Apollo 8 and “conspiracy theorists,” thus exhibit- mission included in “Beacons in the ing the very kind of false pattern recogni- Established 1845 Night,” by John Rennie [From the Editor], tion he claims to expose. Just as all snakes reminds me of a question that has both- with red bands can be mistaken for the pRESIDENT: Steven Yee ered me ever since I saw it in 1968: Why poisonous varieties, all religious people Managing Director, International: Kevin Hause don’t we see any stars in the picture? can be mistaken for those who see the Vir- VICE PRESIDENT: Frances Newburg Ken Larsen gin Mary on the side of a building, all who managing DIRECTOR, consumer mark eting : Salt Lake City seek evidence for extraterrestrial contact Christian Dorbandt can be mistaken for those who see a face associate DIRECTOR, consumer mark eting : Anne Marie O’Keefe on Mars, and so on. Senior Marketing Manager/Retention: This hypocritical dynamic from the Catherine Bussey FULFILLMENT AND DISTRIBUTION MANAGER: mouths of those who would circumscribe Rosa Davis certain “types” of individuals who cannot managing DIRECTOR, online: Michael Harbolt be trusted to think is corrupting our public discourse about science and reason and V IC E PRESIDENT AND PUBLISHER: Bruce Brandfon injecting dangerously authoritarian modes DI REC TOR , global media solutions: of thinking into our political debate. Jeremy A. Abbate vice president, marketing and sales Nelson Leith development: Michael Voss Washington, D.C. SALES DEVELOPMENT MANAGER: David Tirpack SALES REPRESENTATIVES: Gary Bronson, Jeffrey Crennan, Thomas Nolan, Stan Schmidt SHERMER REPLIES: Leith is right that it cannot be “au- thority” by itself that makes the distinction between a PROMOTION MANAGER: Diane Schube RESEARCH MANAGER: Aida Dadurian true and false pattern, between a false negative and ASTRONAUT William Anders took the iconic PROMOTION DESIGN MANAGER: Nancy Mongelli false positive error, between meaningful and mean- “Earthrise” photograph while orbiting the Vice president, finance , and moon in the Apollo 8 spacecraft. ingless patterns, and so on. In politics, we decide on GENERAL MANAGER: Michael Florek which pattern of government we want by voting. But BUSINESS MANAGER: Marie Maher MANAGER, ADVERTISING ACCOUNTING AND RENNIE REPLIES: Many people have wondered in science, we rely on evidence, experimentation, cor- COORDINATION: Constance Holmes about that discrepancy over the years. Stars aren’t roboration, repeatability and the other tools de- visible in the Apollo photographs because the sur- signed specifically to avoid making those types of er- DIRECTOR, SPECIAL PROJECTS: Barth David Schwartz

face of the moon and the earth itself appear so rors in pattern detection. DIRECTOR, ANCILLARY PRODUCTS: Diane McGarvey bright. Because of their brightness, the astronauts PERMISSIONS MANAGER: Linda Hertz had to use short exposures. But the film could not ERRATA “Blocking Sound with Holes,” by Charles handle the level of contrast involved in also picking Q. Choi [News Scan], gives incorrect dimensions for How to Contact Us up the images of the stars, which are many orders of aluminum plates used in the described experiments. magnitude less bright than the moon and the earth The plates were two to five millimeters thick and 20 subscriptions For new subscriptions, renewals, gifts, payments, and in the foreground—both being illuminated by the centimeters wide. changes of address: U.S. and Canada, 800-333-1199; relatively nearby sun. If the moon’s surface were a “Turning Back the Cellular Clock,” by Tim Hornyak outside North America, 515-248-7684 or www.SciAm.com dark color and the earth had not been in the sky, it [Insights],misstates experimental data regarding might have been possible to photograph stars casu- mice implanted with induced pluripotent stem cells reprints To order reprints of articles: Reprint Department, ally, but that was not the case. (iPS cells): 37 mice received iPS cells made with the Scientific American, 415 Madison Ave., Try this experiment on your own: some clear cancer gene c-Myc, and six died. Twenty-six received New York, NY 10017-1111; night with a full moon, point a handheld camera at iPS cells made without c-Myc, and none died. 212-451-8877, fax: 212-355-0408; [email protected] the sky and try to snap a photograph that simultane- ously shows clear details of the moon as well as any permissions stars in the field of view. Neither film nor digital cam- Letters to the Editor For permission to copy or reuse material: Permissions eras can routinely capture such disparate levels of Scientific American Department, Scientific American, 415 Madison Ave., 415 Madison Ave. New York, NY 10017-1111; www.SciAm.com/permissions brightness within a single frame. or 212-451-8546 for procedures. Please allow three to six New York, NY 10017-1111 weeks for processing. or [email protected] ■■ Pattern Police? In “Patternicity” [Skeptic], Michael Sher Letters may be edited for length and clarity. advertising www.SciAm.com has electronic contact information for mer claims that humans evolved to “find We regret that we cannot answer each one. Post a comment on any article instantly at sales representatives of Scientific American in all regions meaningful patterns in meaningless noise,” www.SciAm.com/sciammag of the U.S. and in other countries.

causing people to believe “weird things.” NASA

The Mohole ■ Analog Voice Recognition ■ Our Patent Business Compiled by Daniel C. Schlenoff

APRIL 1959 coins could be carried in considerable APRIL 1859 PLANET OR ESCAPEE?—“In their relatively quantities without inconvenience. The to- SOME SAY ALUMINUM—“It is only a few brief acquaintance with Pluto, astrono- tal nominal value of bronze 5 and 10 cen- years ago that this valuable metal was un- mers have begun to doubt that this object time pieces in circulation is estimated to be common and expensive, owing chiefly to is a planet at all. Pluto’s eccentric orbit is about 56 million francs. It is proposed to the difficulty of reducing it from its oxyde. tilted at a considerable angle to the plane replace some 50 million francs’ worth of We believe that about three years ago, its of the ecliptic, in which the orbits of the these with aluminium coins of the same market value was no less than $18 per other planets lie. Even on its closest ap- denominations. About 2,000 tons of alu- ounce. In a very outcast region of the proach to our region of the solar system, it minium, worth 44 cents a pound in blanks world—on the west coast of cold Green- will shine no brighter than Triton, one of ready for stamping, will be required.” land—an aluminous mineral called cryolite Neptune’s two satellites, suggesting that it has been discovered in great quantities, is no larger. There is suspicion that Pluto is from which the metal can be reduced at a an illegitimate offspring of Neptune, a very limited cost, and a large factory satellite that escaped, as two man- has lately been erected at Battersea, made satellites recently did, to England, by M. Gerhard, for this ply its own orbit around the very purpose. He has been able sun. —Owen Gingerich” to sell it for about one dollar per ounce. Aluminum is the THE DEEPEST HOLE—“The lightest of all the metals. crust of the earth is a rela- This quality should rec- tively thin film over the ommend it for coinage, to earth’s interior. Its aver- take the place of coins of age thickness is some 10 the lowest value.” miles, a mere 400th of the earth’s radius. Beneath the PATENT AGENCY—“The crust lies the mantle; impor- United States Patent Office, tant details of its composition located at Washington, is the and character are uncertain. storehouse and monument of the These can only be determined by di- ingenuity of our countrymen. Be- rect examination. The boundary because of the value of many of the inven- tween crust and mantle is the Mohorovicic tions for which patents are sought, and the discontinuity, known to earth scientists as THE SCIENTIFIC AMERICAN Patent Agency, great necessity that the papers be carefully the Moho. To obtain a sample of the man- New York City, 1859 prepared, there has grown up a profession, tle, we must drill a hole through the Moho: the members of which are usually desig- a Mohole. —William Bascom” VOICE RECOGNITION—“A safe lock has nated ‘patent agents’ or ‘patent solicitors,’ been invented which is provided with a and who have become as much a necessity [NOTE: Work on the unfinished Mohole was phonographic mechanism so that it can be for the proper transaction of business with abandoned in 1966.] opened only by the voice of the owner. A the Patent Office as the lawyers are in our mouthpiece like that of a telephone takes courts of justice. We will here state, in ref- the place of a knob on the door, and this is erence to ourselves, what no one will pre- APRIL 1909 provided with the usual needle, which trav- sume to deny, that since 1846, the Scientif- lighter MONEY—“Experiments in abra- els in a groove in the sound record of the ic American Patent Agency Department sion conducted at the French mint have phonograph cylinder. Before the safe can has examined into the novelty of more in-

VOL. XIV, NO. 32; APRIL 16, 1859 proved that aluminium coins will be less be unlocked, the password must be spo- ventions than any other patent agents now rapidly worn by use than coins of gold, sil- ken into the cylinder by the one who made living in this country. We present to our ver, or even bronze. The metal’s extreme the original record. The report does not readers an illustration of the interior view lightness is another advantage: it is four state what would occur if the owner should of the ‘Scientific American’ and patent

SCIENTIFIC AMERICAN, SCIENTIFIC times lighter than silver. Hence aluminium come down to his office with a bad cold.” agency office, New York.”

Fingerprint Feeling ■ Stem Cell Progress ■ Moon’s Backside ■ Even Higher Seas Edited by Philip Yam

■ Sensation Swirls tients’ existing immune cells. same way, it would have more stead cluster on the trailing Those fingertip whorls aren’t Injected back into the pa- craters on its leading side, edge, suggesting that it was just good for gripping objects tients, the stem cells apparent- where it encountered heavy once in front. An asteroid and identifying people; they ly “reset” the body’s defenses bombardment during the early or comet strike could have also enable you to feel fine so that they do not mistakenly years of the solar system [see spun the moon 180 degrees textures and tiny objects. go after healthy tissue. The “The New Moon”; SciAm, to its current orientation. French researchers construct- study, published online Janu- December 2003]. Younger The journal Icarus posted the ed two mechanical sensors, ary 30 in the Lancet Neurolo- craters follow this pattern, but conclusion online on Decem- one with gy, involved only 21 patients, older craters do not; they in- ber 31, 2008. —John Matson a ridged however, so more complete end tip trials are needed to assess the ■ Melting Mess and an- approach. New details are emerging on how the melting poles could other with Data on stem cell therapies raise ocean heights [see “The Unquiet Ice”; SciAm, Febru- a smooth in general should increase ary 2008]. Researchers at the University of Toronto and one; they soon: the U.S. Food and Drug Oregon State University suggest that the rise could be un- then ran Administration approved in even around the world. They examined the West Antarctic them over January the first human em- ice sheet, which contains enough grounded ice to boost various bryonic stem cell trial—a deci- global sea levels by five meters if it splashed into the water. textured sion long awaited by scientists But such a huge redistribution of mass in Antarctica would surfaces, measuring the vibra- [see “The Stem Cell Chal- reduce the gravitational pull in the area and shift the tions picked up by the finger- lenge”; SciAm, June 2004]. It earth’s rotation axis by 500 meters. Taking these and oth- printed sensors. Each ridge will enable Geron Corpora- er factors into account, they figure that the seas will drop magnified the frequency tion in Menlo Park, Calif., to near Antarctica but rise in the Northern Hemisphere by an range well suited for detection test embryonic stem cells on additional one to two meters above previous estimates. by nerve endings in the skin 10 patients with spinal cord Gravitate toward the analysis in the February 6 Science. called Pacinian corpuscles. injuries. —Kate Wilcox The work, published online on the rise: Antarctic ice January 29 by Science, helps ■ Mooned by the Moon could raise sea levels unevenly

around the globe. ) to explain how the sense of Some four billion years ago moon (

touch accurately informs our the far side of the moon may A S A

surroundings [see “Worlds of have faced Earth. Mark Wiec- N Feeling”; SciAm Mind, De- zorek and Mathieu Le Feuvre nd cember 2004]. —Kate Wilcox of the Institute of Earth Phys-

ics in Paris propose that if the y of NSSDC a s ■ Forward with Stem Cells moon had always faced the Researchers at Northwestern ); Courte ice University stopped and, in ( some cases, reversed the effects of early-stage multiple Getty Images sclerosis, a disease in which m OH the immune system attacks the central nervous system. JoeS ); The investigators removed fingerprint from the bone marrow so- ( called hematopoietic stem

cells, which resupply the body Getty Images with fresh blood cells, then OUT OF SIGHT: The far side of

used drugs to destroy the pa- the moon, as seen by Apollo 16. SethJoel

BIOLOGY Evolution in a Bottle Self-replicating RNAs advance science another step toward artificial life By W. Wayt Gibbs

erald F. Joyce admits that when he In January, one month before the bi- competed with the others for the common saw the results of the experiment, centenary of Charles Darwin’s birth, they pool of building blocks. And the repro- G he was tempted to halt further announced the results in Science. Their duction process was imperfect, so new work and publish the results immediately. little test-tube system did indeed manifest mutants—Joyce calls them recombi- After years of trying, he and his student nearly all the essential characteristics of nants—soon appeared and even thrived. Tracey Lincoln had finally found a couple Darwinian evolution. The starting 24 “We let it run for 100 hours,” Joyce re- of short but powerful RNA sequences that RNA variants reproduced, some faster calls, “during which we saw an overall am- when mixed together along with a slurry than others depending on the environ- plification in the number of replicator mol- of simpler RNA building blocks will dou- mental conditions. Each molecular species ecules by 1023. Pretty soon the original ble in number again and again, replicator types died out, and expanding 10-fold in a few the recombinants began to take hours and continuing to repli- over the population.” None of cate as long as they have space the recombinants, however, and raw material. could do something new—that But Joyce was not fully sat- is, something that none of its isfied. A professor and dean at ancestors could perform. the Scripps Research Institute That crucial missing ingre- in La Jolla, Calif., the 53-year- dient still separates artificial old molecular chemist is one of evolution from true Darwin- the founding champions of the ian evolution. “This is not “RNA world” hypothesis. alive,” Joyce emphasizes. “In That is the notion that perhaps life, novel function can be in- life as we know it—life based vented out of whole cloth. We on DNA and enzymatic pro- don’t have that. Our goal is to teins, with RNA acting for the make life in the lab, but to get most part as a mere courier of there we need to increase the genetic information—evolved complexity of the system so out of a simpler, prebiotic that it can start inventing new chemical system based mostly function, rather than just opti- or even solely on RNA. Of mizing the function we’ve de- course, the idea is plausible signed into it.” only if RNA can support evo- That goal clearly seems pos- lution on its own. Maybe, sible, because the R NA replica- Joyce thought, his synthetic tors in Joyce’s lab were relative- RNA could help prove that ly simple: each has only two possible. So he and Lincoln genelike sections that can vary. spent another year working Each of those “genes” is a short

Photo Researchers, Inc. with the molecules, mutating GROWING LIFE: Reproducing molecules of RNA branch out horizontal- building block of RNA. A rep- them and setting up competi- ly from a central spine of DNA. Such RNA can now demonstrate most licator, being an R NA enzyme, tions in which only the fittest of the essential aspects of evolution in a test tube. For synthetic life, can gather the two genes and

oscar l. miller l. oscar would survive. however, they also need the ability to evolve brand new functions. link them together to create an

enzyme that is the replicator’s “mate.” The neering work with DNA enzymes, hopes The next big step toward the creation mate is set free and gathers two loose that “by capturing Darwinian evolution of life in the lab, Joyce says, will be to en- genes, which it assembles into a clone of in new molecules, we might be able to bet- gineer (or evolve) a set of synthetic mole- the original replicator. Recombinants ap- ter understand the basic principles of bio- cules that can perform metabolism as well pear when a mate is unfaithful and links logical evolution,” much of which is still as replication. Geneticist Jack W. Szostak up genes that were never meant for each somewhat mysterious at the molecular of Harvard Medical School has developed other. Recombinants did not, however, level. Joyce and Lincoln, for example, no- nonbiological proteins that bind ATP, an create genes. It may be possible to engineer ticed in their postmortem examination of energy-carrying chemical crucial to me- a system that does, or to add complexity by the experiment that the three most suc- tabolism. Szostak’s lab is also attempting giving each replicator more genes with cessful recombinants had formed a clique. to fashion protocells that encase RNA which to work. Whenever any clique member made a re- within tiny spheres of fatty acids, called Scott K. Silverman, a chemist at the production error, the result was one of the micelles, that can form, merge and repli- University of Illinois who has done pio- other two peers. cate spontaneously. Even if biochemists do manage to cob- ble RNA and other basic compounds into From Test-Tube Life to Diagnostic Tools some form of synthetic life, the engineered system will probably be so complex at first Creating life in the laboratory would be a momentous occasion for humanity, even if it is that it will hardly prove that natural life more molecular than Frankensteinian. But there may be more mundane uses for such chem began in some similar way, four billion istry. A paper in press at Nature Biotechnology, Gerald F. Joyce says, describes how his lab years ago. Joyce’s replicators consist of a at the Scripps Research Institute in La Jolla, Calif., has modified RNA replicators so that they must perform a biochemical function to reproduce. The winners of that evolutionary race mere 50 chemical letters, but the odds of will be good candidates for a medical diagnostic, he thinks. Scott K. Silverman of the Uni such a sequence appearing by chance are versity of Illinois says the idea has merit: “Suppose you need to do detection in a dirty envi roughly one in 1030, he notes. “If it were ronment with lots of different chemicals present—say you want to find Salmonella inside six or even 10 letters long, then I’d say we peanut butter. That’s hard to do without purification steps. It would be useful to be able to might be in the realm of plausibility, where evolve the diagnostic system so that it still finds the signal despite all the noise.” —W.W.G. one could imagine them assembling spontaneously” in the primordial soup.

MICROFLUIDICS A Chip against Cancer Evaluating tumors and their treatment via a blood sample By Elaine Schattner

ancer therapy is too often a matter of Toner, leader of the team that engineered Mechanical Systems Resource Center. Cchance. Despite advances in cancer the device at Boston’s BioMicroElectro- Toner likens his new system to the way

genetics, physicians have only limited in- AIDS patients have their viral load and enter formation to make decisions about indi- T cells measured so that their medication vidual patients. People undergo treatments can be adjusted. “It could be the same for esource C with their fingers crossed, not knowing if cancer,” he offers. R they will be helped or harmed. Most carcinomas shed malignant cells MEMS A group at Massachusetts General that enter the bloodstream and dissemi-

Hospital might have a way to personalize nate, sometimes latching on to new areas ospital Bio cancer care more effectively. It is currently where they form tumors. These circulat- refining and testing a lab-on-a-chip that ing tumor cells (CTCs) constitute just a can sample and analyze the circulating tu- tiny fraction of blood cells, often fewer mor cells from just a teaspoon of a pa- than one in a million, in patients with met- STUCK ON YOU: In the CTC-chip, a lung cancer tient’s blood, obviating the need, in many cell is caught by a microscopic post coated astatic disease; they are even less abun- assachusetts General H patients, for sometimes dangerous biop- with an antibody that binds to a surface dant in patients with limited, early-stage sies. “The chip will allow rational decision protein on tumor cells. Each post is 100 tumors that have not overtly spread. The ourtesy of M making for cancer patients,” says Mehmet microns in diameter and 100 microns tall. researchers realized that CTCs, though C

rare, offer a potential window into the In their first test of the chip, described “It’s an enormous advance in our abil- real-time dynamics of a tumor’s biology. in the December 20, 2007, Nature, the re- ity to monitor patients,” comments Roy The team has adapted microfluidics searchers used blood samples from 116 pa- Herbst, a thoracic oncologist at the Uni- technology, developed during the past 25 tients with lung, prostate, pancreatic, versity of Texas M.D. Anderson Cancer years to analyze tiny amounts of fluid and breast or colorectal cancer and successful- Center, who was not involved in the work. gas, to capture those uncommon cells. ly isolated CTCs in all but one case. The By providing a noninvasive method to fol- Like other microfluidics instruments, the CTC-chip finds cancer cells as rare as one low the quantity and quality of tumor CTC-chip, as the group calls it, comprises in a billion blood cells, making it at least cells, the chip “offers the possibility of a silicon-etched chip fitted with micro- 100-fold more powerful than the most personalized medicine and hence effective scopic columns, a chamber to enclose the widely used conventional method, which therapy,” he says. fluid and chip, and a pneumatic pump. The requires incubating a large blood sample For the 215,000 people in the U.S. di- columns, or microposts, function as min- with antibody-coated microbeads. The agnosed with lung cancer every year, the iature test tubes where cells and chemicals cells are also in better condition for analy- need for better diagnostic tools is particu- can mix, adhere and undergo evaluation. sis than those prepared using microbeads. larly urgent, says Toner’s collaborator The CTC-chip relies on 78,000 micro- In another trial, the investigators used Thomas Lynch, chief of the center for tho- posts to grab cancer cells from a mix of the chip to evaluate tumor genetics in 27 racic cancers at Mass General. In lung normal blood components as they mean- patients with lung cancer. In work pub- cancer patients, even a small biopsy bears der through the system via exquisitely con- lished in the July 24, 2008, New England risk of blood loss, infection and, in rare in- trolled suction. The posts are coated with Journal of Medicine, they identified rele- stances, collapse of the affected lung. antibodies to the epithelial cell adhesion vant genetic abnormalities in CTCs from Herbst cautions that the findings need molecule (EpCAM). Nearly all carcinoma most cases and noted in some patients to be validated in larger clinical trials and cells bear EpCAM at the surface, where it emerging mutations that confer resistance at other medical centers. At Mass General, plays a key role in directing how cells bind to tyrosine kinase inhibitors, the type of the researchers are now evaluating how to one another, signal and migrate. Nor- medication the patients were taking. In well the chip measures cancer growth and mal blood cells lack EpCAM, so only the the past, repeat biopsy would have been responses to treatment in patients with malignant cells stick to the antibodies on necessary to establish these kinds of genet- breast, ovarian and prostate cancers. the microposts. ic changes. By direct examination of cancer cells in blood, the CTC-chip might also uncover new targets for therapy and help deter- Getting Personal with Cancer Care mine when and how metastases arise. Toner sees unlimited possibilities once the Cancer therapies often fail because of genetic differences among individuals. In personal chip has proved itself in bigger clinical ized cancer care, physicians would tailor treatment to the particular features of each pa tient’s cancer. For example, colon cancer patients often receive treatments with antibodies studies. In the future, he remarks, it could directed at a growth factor receptor. Although this therapy, costing nearly $10,000 per become a screening tool to find nascent month, can prolong life and make some patients feel better, it works only in those who have cancers and even “could be used at annual the normal version of K-ras, a gene for a signaling protein crucial for tumor growth. So if checkups.” physicians examine the tumors for K-ras mutations before prescribing these drugs, they can direct care to those it would help, sparing others the costs, hassle and possible side effects of treatment. —E.S. Elaine Schattner is a science writer and oncologist based in New York City.

PARTICLE PHYSICS Colliding Philosophies A novel way to rummage for particles in accelerator debris BY DAVIDE CASTELVECCHI

fter a false start in 2008, the Large this October. The LHC may or may not approach to analyzing data could help AHadron Collider (LHC), the glitzy end up spewing out dark matter, mini physicists make sure they don’t miss any of new atom smasher at CERN (the Europe- black holes or other exotica. But whichev- the good stuff. an laboratory for particle physics) near Ge- er way, figuring what’s coming out will be The LHC and other accelerators such as neva, is finally due to start its experiments a tremendously hard task. A controversial the Tevatron at the Fermi National Accel- www.SciAm.com © 2009 SCIENTIFIC AMERICAN, INC. SCIENTIFIC AMERICAN 11 News Scan

erator Laboratory in Batavia, Ill., push gent test to date, says Knuteson, who protons or other particles to near light has since left active research. speed and smash them together. Thanks Physicist Louis Lyons of the Univer- to Albert Einstein’s E = mc2, some of sity of Oxford says the team’s statistics that collision energy turns into rare, were sound. But Pekka Sinervo, a Uni- heavy particles that almost immediate- versity of Toronto physicist who is in- ly decay into hundreds of more mun- volved in both Tevatron and LHC ex- dane particles (of which many dozens periments, remains unconvinced. “The of different types are known). The authors had to sweep a lot of poorly LHC’s huge detectors will record the understood effects ‘under the carpet’ passage of this debris and produce data and not address them directly,” Siner- at a staggering rate, equivalent to one vo states, meaning that the search gen- Collision point in accelerator experiments is CD-ROM per second. where new particles emerge. A novel technique erated an abundance of hard-to-inter- Physicists will rummage through could uncover unpredicted particles. pret signals. Still, global searches could the information for particular combi- have some utility, he concedes, as long nations of decay products that would sug- a particular word, matches every single as they do not distract researchers from gest a new particle has been created. They word against the dictionary of known searches targeted at specific phenomena, will be looking for signs of the Higgs bo- words and flags the ones that sound as if adding that he is “not convinced that one son, the long-sought particle that is sup- they might belong to a foreign language. would be able to use such a search for an posed to give other particles their masses, To limit false positives—sometimes early discovery at the LHC.” and also for entirely new particles that mundane particles will interact and mimic That may be true, remarks Sascha Ca- could give a first glimpse of the laws of the behavior of other, more interesting par- ron, a physicist from the University of physics at higher energies. ticles—physicists can set a threshold for Freiburg in Germany, but nonetheless But some fear that this traditional ap- the minimum number of times a strange much of the particle physics community proach—akin to running a computer algo- event may occur before alerting the exper- has warmed to the idea of global searches rithm through a text searching for the let- imenters of something possibly new. “We since Knuteson first proposed it early in ters H-I-G-G-S—could end up missing in- take into account the fact that we look at this decade. Caron and his collaborators teresting new signatures that no one had a lot of different places,” Knuteson says. have developed their own software for foreseen. At Fermilab, Bruce Knuteson Knuteson, Mrenna and their collabora- what they call general searches while and Stephen Mrenna have for some years tors put their method to work on old Tev working at an experiment at the DESY advocated a more “holistic” approach atron data. In principle, exotic particles laboratory in Hamburg, and they plan to called global search. Instead of looking could have been lurking where no targeted do the same at the LHC. for particular signatures, they wrote soft- searches had looked before. The team Experience at the Tevatron also shows ware that analyzes all the data and com- found nothing of particular statistical rel- that global searches could help physicists pares them with predictions of the so- evance, so they made no claims of new dis- understand how to interpret data, Mren- called Standard Model, which comprises coveries. But that effort at least showed na points out—for example, how the de- tudio

the known set of laws of particle physics. that global searches do not necessarily tectors react to various particles. Teams ox S b

The software then flags any deviations lead to many false positives, as some phys- rarely compare notes, so that their as- and from the Standard Model as potential new icists feared. The results, which appear in sumptions are potentially in contradic- particles. It is a bit like having an algo- the January Physical Review D, also con- tion. “If you look at everything, every- ourtesy of S rithm that, instead of searching a text for stitute the Standard Model’s most strin- thing has to make sense,” Mrenna says. C

SENSES Finding Balance Is poor posture control the real cause of motion sickness? By Brendan Borrell

o avoid a potentially nasty cleanup, chamber. Inside, they step onto a force- and forth on a track—a mere 1.8 centime- Tstudents are deprived of food for four sensing platform and stare at a paper map ters with each cycle. At the right frequen- hours before entering the experimental of the U.S. The walls begin sliding back cies, this movement triggers a tugging sen-

sation that begins somewhere in the brain and mysteriously travels to the belly. But before the full effects of motion sickness set in, the subjects will typically turn away and beg for mercy. At that point, the students may be thinking that the course credit they will receive for participating in Thomas Stof- fregen’s sensory funhouse may not be worth it. But for the University of Minne- sota psychologist, every student he lures inside is another data point that he be- lieves will overturn the dogma about the cause of motion sickness. If he is right, the findings could lead to new ways of identifying people susceptible to motion sickness before they get sick and may provide designers of simulators and video games with ways to keep controllers in the hands dancy is an essential part of the sensory NAUSEATING: Thomas Stoffregen monitors a of potentially woozy players. system, and our brains do not compare volunteer as an assistant moves the walls For the past century, scientists have be- our senses in any direct manner. More- back and forth to induce motion sickness. lieved that motion sickness derives from a over, because it is impossible to determine conflict among our senses. Our inner ears which of the conflicting senses is interpret- in 1991, landed with a dull thud, and his contain sensors for both angular motion ed as being “wrong” by an individual’s papers garner just a handful of citations (the semicircular canals) and linear mo- brain, Stoffregen has branded the conflict each year. But experts have been mutter- tion (the otoliths). When these sensors dis- theory with the highest-order insult a sci- ing privately about Stoffregen ever since — agree with the information we expect to entist can muster: unfalsifiable. and lately some have grudgingly begun to receive from our eyes and muscles, motion Indeed, researchers have long won- accept him. “It was a very, very different sickness manifests itself. And yet, Stoffre- dered why some individuals and certain theory,” says Larry Hettinger, a longtime gen says, our senses constantly provide classes of people—children and pregnant motion sickness researcher now at defense different channels of information: redun- women—are more susceptible to motion contractor Northrop Grumman. “I clear- sickness than others. What is more, exper- ly remember people thinking, ‘This is non- iments conducted since the dawn of the sense, this is crazy foolishness.’” Space Age, when NASA wanted to prevent The growing acceptance of Stoffregen’s its astronauts from falling ill, can predict view has much to do with experiments ) who will succumb to motion sickness with conducted over the past two decades. In- bottom ( only about 30 percent accuracy. Finally, side the moving room, he has found that Stoffregen notes the puzzling observation volunteers can significantly reduce motion — GettyImages that, whereas people may feel sick on the sickness simply by widening their stance ks deck of boat, they rarely get the urge to an observation, he says, not predicted by SAC vomit when fully immersed in water. sensory conflict theory. Students standing avid D

); Stoffregen instead argues that motion with their feet five centimeters apart tend top ( sickness comes from the brain’s persistent to get motion sickness about 60 percent of inability to modulate the body’s move- the time. Spreading their legs to 30 centi- ments in a challenging environment. Pos- meters increases the stability of the head tural instability—the inability to maintain and torso and decreases the incidence of

UniversityMinnesotaof balance—was considered a symptom of motion sickness to about 20 percent. Stof- motion sickness. Not so, Stoffregen says. fregen says that by monitoring body sway, Although postural control relies on senso- he can predict the onset of motion sickness ry feedback, motion sickness is really a with 60 percent accuracy. If swaying is atricko’leary P ROCKING THE BOAT: A maverick theory claims sign that the motor-control system is go- just a symptom of motion sickness, it that motion sickness arises from postural ing haywire. would be detectable only after partici- ourtesyof

C instability, not sensory conflict. His alternative theory, first published pants reported feeling sick.

But the ultimate test of his theory is still Blair Witch Project. Stoffregen just needs to prevent motion sickness in orbital in the works. Floating in water, the human to convince NASA—and a dozen amphibi- flight,” he says. “Sadly, water-filled space- body becomes passively stable, and pos- ous students—to let him use the Neutral craft would be so heavy that they would tural control is no longer an issue. If Stof- Buoyancy Laboratory at the Johnson be too expensive to launch.” There’s al- fregen is right, then under such a condi- Space Center in Houston. Unfortunately, ways Dramamine. tion, motion sickness would be impossi- the practical applications of that research ble, even if subjects were forced to endure would be tenuous at best. “I think that Brendan Borrell is a freelance writer the nausea-inducing camerawork of The water immersion would be a surefire way based in New York City.

BEHAVIOR Thriving on Selfishness Why it pays for cheaters to punish other cheaters By Marina Krakovsky

t’s the altruism paradox: If everyone in a As Eldakar puts it, “If you’re a single self- to punish other cheaters, members of the Igroup helps fellow members, everyone is ish individual in a group of altruists, the group do not balk as long as they benefit. better off—yet as more work selflessly for best thing you can do evolutionarily is to And when selfish punishment works well, the common good, cheating becomes make sure nobody else becomes selfish— benefit they do. In a colony of tree wasps tempting, because individuals can enjoy make sure you’re the only one.” That is (where workers care for the queen’s off- more personal gain if they do not chip in. why, he points out, some of the harshest spring instead of laying their own eggs), a But as freeloaders exploit the do-gooders, critics of sports doping, for example, turn special caste of wasps sting other worker everybody’s payoff from altruism shrinks. out to be guilty of steroid use themselves: wasps that try to lay eggs, even as the vig- All kinds of social creatures, from hu- cheating gives athletes an edge only if ilante wasps get away with laying eggs mans down to insects and germs, must their competitors aren’t doing it, too. themselves. In a strange but mutually ben- cope with this problem; if they do not, Although it is hypocritical for cheaters eficial bargain, punishing other cheaters cheaters take over and leech the group to earns punishers the right to cheat. death. So how does altruism flourish? In the year since Eldakar and Wilson Two answers have predominated over the wrote up their analysis, their insights years: kin selection, which explains altru- have remained largely under the radar. ism toward genetic relatives—and reci- But the idea of a division of labor between procity—the tendency to help those who cooperators and policing defectors ap- have helped us. Adding to these solutions, peals to Pete Richerson, who studies the evolutionary biologist Omar Tonsi Elda- evolution of cooperation at the University kar came up with a clever new one: cheat- of California, Davis. “It’s nothing as com- ers help to sustain altruism by punishing plicated as a salary, but allowing the pun- other cheaters, a strategy called selfish ishers to defect in effect does compensate punishment. them for their services in punishing other “All the theories addressed how altru- defectors who don’t punish,” he says. Af- ists keep the selfish guys out,” explains El- ter all, policing often takes effort and per- dakar, who described his model with his sonal risk, and not all altruists are willing Ph.D. thesis adviser David Sloan Wilson of to bear those costs. Binghamton University in May 2008. Be- Corrupt policing may evoke images of cause selfishness undermines altruism, al- the mafia, and indeed Eldakar notes that truists certainly have an incentive to pun- when the mob monopolizes crime in a ish cheaters—a widespread behavior pat- neighborhood, the community is essen- tern known as altruistic punishment. But tially paying for protection from rival Getty Images cheaters, Eldakar realized, also have rea- DO AS I SAY, NOT AS I DO: Athletes who have gangs—a deal that, done right, lowers son to punish cheaters, only for motives of used illicit performance-enhancing drugs, crime and increases prosperity. But mob their own: a group with too many cheaters such as Yankee third baseman Alex Rodri- dynamics are not always so benign, as

does not have enough altruists to exploit. guez, can also be their harshest critics. the history of organized crime reveals. jeffzelevansky

“What starts out as a bunch of goons that mix is an optimal mix,” he explains. evolves without selfish punishment. In a with guns willing to punish people [for The answer to that problem, he says, is software simulation, Eldakar and Wilson breaching contracts] becomes a protec- competition not between individuals in a have found that as the cost of punishing tion racket,” Richerson says. The next group but between groups. That is be- cheaters falls, so do the number of selfish question, therefore, is, What keeps the cause whereas selfishness beats altruism punishers. “When punishment is cheap, selfish punishers themselves from overex- within groups, altruistic groups are more lots of people punish,” Wilson explains. ploiting the group? likely to survive than selfish groups. So al- And among humans, there is no shortage Wilson readily acknowledges this limi- though selfish punishment aids altruism of low-cost ways to keep others in line— tation of the selfish punishment model. from within a group, the model also bol- from outright ostracism to good old-fash- Although selfish punishers allow cooper- sters the idea of group selection, a concept ioned gossip. ators to gain a foothold within a group, that has seen cycles of popularity in evo- thus creating a mix of cheaters and coop- lutionary biology. Marina Krakovsky is based in the erators, “there’s nothing telling us that What is more, altruism sometimes San Francisco Bay Area.

ECOLOGY Snakebit Southern California sees a rise in extratoxic venom By Michael Tennesen

apid muscle twitching, as if a person crease. Most rattlesnakes warn off poten- toxins and hemotoxins, which damage tis- Rhad snakes crawling under the skin, tial predators by shaking their noisy sue and disrupt blood clotting. But the is the telltale sign to Roy Johnson that the tails—that is what the red rattlesnake and Southern Pacific also produces a neurotox- Southern Pacific rattlesnake has struck. the speckled rattlesnake, southern Cali- in, which is more serious because it quickly On occasion, this symptom can progress fornia’s other two dominant coastal spe- affects breathing and muscle control. An- to difficult breathing, coma and death. cies, tend to do. But the noise also makes ecdotal reports suggest that the snake’s This snake’s bite is one of the few to in- the reptiles more likely to end up on the venom contains more neurotoxin than it duce neurological symptoms, in contrast killing end of a shovel if the did a few years ago. Richard Dart, director to most other rattlesnake bites, which ini- threat is human. In con- of the Rocky Mountain Poison and Drug tially produce swelling and bruising trast, Southern Pacific Center in Denver, does not rule out around the wound, notes Johnson, a phy- rattlesnakes are more that the species could have made sician in Palomar, Calif., who has treated apt to lay low or its venom more toxic, perhaps some 700 snakebite cases. Increasingly, move away than by crossbreeding with the more the proportion of rattlesnake bites in hiss and rattle deadly, desert-dwelling Mo- southern California are skewing to those when confronted, jave green rattlesnake or by like the more deadly Southern Pacific spe- a strategy that may turning on dormant genes devel- cies, and scientists are not sure why. boost their chances oped over time in response to more Every year the Centers for Disease Con- of surviving, John- resistant prey. trol and Prevention logs 7,000 reports of son says. He specu- The amount of neuro- snakebites in the U.S., which lead to about lates that by club- toxin is indeed dramat- 15 deaths. Roughly 25 percent of the sur- bing its competitors, ic compared with the vivors incur some permanent damage. In humans have paved the creature’s close cous- southern California, reports from area way for the Southern Pacific in, the Northern Pacif- hospitals and medical centers show a spike to move into new areas. That animal “is ic rattler. This species in serious bites—the facilities say that, adapting to human habitats much like the preys on ground and where they formerly saw patients with se- coyote—whether we like it or not,” John rock squirrels, which by six vere neurological symptoms once every son remarks. VICIOUS VENOM: Unlike two to three years, they now see several of The rising incidence of supertoxic Getty Images most other rattlers, g these types of envenomations every year. bite cases could also reflect a change in the Southern Pacific oun Y Johnson, for one, suspects that hu- the species’ venom. To predigest their rattlesnake has erry J mans themselves are to blame for the in- prey, most rattlers produce so-called cyto- a neurotoxic bite.

weeks of age develop a natural resistance Still, Hayes does not believe that the the “people-biting snake in California” to withstand a full envenomation, sug- rattler’s venom has become more toxic. and attributes the increase in incidents to gests research at the University of Califor- Rather he thinks that people are becom- humans encroaching on the animal’s nia, Davis. The Southern variety, howev- ing less tolerant of snake venom, perhaps coastal and mountain habitat. We are, er, has enough neurotoxin to overcome because of “pollution weakening human Bush says, “only now learning how potent any such natural resistance, says biologist lungs and the immune system.” and varied rattlesnake venom can be.” William Hayes of Loma Linda University. Sean Bush, a treating physician at “Southern Pacifics have no problem get- Loma Linda University Medical Center, Michael Tennesen is a freelance science ting lots of squirrels.” says that the Southern Pacific is definitely writer based near Los Angeles.

PALEONTOLOGY Supersized Serpent

ossilized remains of a boa constrictor cousin that stretched 13 meters long Fand tipped the scales at more than a ton represent the largest snake ever found. The creature, dubbed Titanoboa cerrejonensis, lived some 60 million years ago in a neotropical rain forest in what is now northeastern Colombia. Identified on the basis of vertebrae recovered from an open-pit coal mine, Titanoboa is believed to have dined on crocodiles, among other creatures. JUMBO BACKBONE of the 13-meter-long fossil In addition to expanding the known limits of snake biology, the ancient ser- snake Titanoboa dwarfs the vertebra of pent contains clues to primeval rain forest climate. Because snakes and other a 5.2-meter-long modern Anaconda. reptiles are “cold-blooded,” or poikilothermic, their body temperature—and hence their life processes—is dependent on that of the surrounding air. The warmer the air is, the larger they can grow. Scientists calculate that to attain its behemoth body size (which bests that of the modern-day record holder, a reticulated python, by nearly three meters), Titanoboa would have to have inhabited an environment with a mean annual temperature of at least 30 to 34 degrees Celsius (86 to 93 degrees Fahrenheit)—significantly toastier than today’s typical tropical forecast of 24 to 26 degrees C. Some climate models predict that equatorial locales have been relatively sheltered from the effects of the planet’s natural “greenhouse” phases, but the evidence from Titanoboa indicates that during these events, places that were already hot actu-

ally got hotter. In fact, shortly after Titanoboa’s reign, tropical temperature may have risen so much as to cause widespread ) heat-related death, although the researchers have not yet found empirical evidence of the effects of such a scorching episode. The findings were published in the February 5Nature. —Kate Wong vertebrae comparison vertebrae ( FEEDINg the beast: Titanoboa is believed to have preyed on crocodiles and other vertebrate creatures that shared its tropical habitat. UF PhotographyUF arson C ay ay R ourtesyof C ); illustration itanoboa T ason Bourque ( ourtesy of J C

HEARING BIOTECH Anti-Loudness Protein Sonic Heat for Genes Fans of club music and rock concerts who like the Heating from sonic waves can turn on genes in the body, demonstrate research- volume cranked up to 11 but want to save their ers at the University Victor Segalen Bordeaux in France and their colleagues. hearing might someday pop a pill rather than plug- Using mice engineered with a bioluminescent gene containing a heat-sensitive ging their ears. Scientists have pinpointed the bio- stretch of DNA, they focused high-intensity ultrasound pulses on a 0.5-milli- chemical mechanism in ears that works to limit meter-wide patch of the mice’s legs, heating up that area just below the skin’s damaging effects of loud sound. When a noise reg- surface to about 43 degrees Celsius (109 degrees Fahrenheit). Light given off isters in the brain as too loud, the protein nAChR, revealed that the gene became active. The technique could help gene therapy, located on sensory hair cells in the inner ear, kicks which introduces beneficial DNA into patients. When and where these genes in to limit the ability of the hair cells to respond. are expressed is paramount, and currently small-molecule drugs and ionizing Mice genetically altered to produce a more potent radiation are employed to switch genes on. But chemicals are not precise, and nAChR could not hear soft sounds, and they suf- rays can trigger cancer. The challenge for ultrasound activation, published Jan- fered less permanent damage to their hearing when uary 27 by the Proceedings of the National Academy of Sciences USA, is safe- scientists blasted 100-decibel noise at their ears. ly getting the waves deep enough to reach organs. —Charles Q. Choi “We know some drugs can modify the protein,” says Paul Fuchs of Johns Hopkins University, who pub- EVOLUTION lished the findings in the January 20PLoS Biology. “But we need to know more about specific amounts” A Beetle’s Menu Change before a sound-protecting drug can be made. So No points for guessing what dung beetles eat. Feces are so rich with nourish- don’t toss the earplugs yet. —Kate Wilcox ing bacteria that 80 or more species of the beetle can live in the same area. Un- der such intense competition for droppings, one species has gone entirely from scavenging to preying. Through 11 months of recording with infrared cameras in the Peruvian jungle, Trond Larsen of Princeton University and his colleagues found that an eight-millimeter-long nocturnal dung beetle, Deltochi- lum valgum, devours millipedes up to 13 times larger than itself. The beetle kills by wrapping its legs around a victim, wedging its serrated head between the prey’s segments and then ripping the body apart. The head of this species is unusually narrow for dung beetles—all the better to burrow inside a corpse to dine on the innards, the researchers note in their report, published online CONCERT fans could get a pill to save their hearing. January 21 by Biology Letters. —Charles Q. Choi

Data Points Annual number of deaths Number of trees in Tree Termination per 1,000 trees in: study area in: 1984: 7.1 1984: 58,736 Trees in the western U.S. have died 2001: 11.4 2001: 47,641 off at an increasing rate over the past few decades, finds Phillip J. van Mantgem of the U.S. Geolog Calculated increase in annual ical Survey and his colleagues. number of deaths They studied various plots in per 1,000 trees: 4 three regions: the Pacific y matt collins matt y Northwest, California and the b Number of years for the tree continental interior near the mortality rate to double in: Rocky Mountains. The culprit Pacific Northwest: seems to be locally higher 17

); illustration illustration ); temperatures, which decrease California: 25 fans

( the available water and boost Continental interior: 29 the activity of a bark-damaging fungus. As a result, trees on average SOURCE: Science, January 23, 2009

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OCEAN CHEMISTRY A Calcium Conundrum Explained In Brief LEAVES FOR LEAVING ALONE Fish excrement could solve a decades-old ocean mystery. After marine plankton die, The vast majority of grasses retain their their calcium carbonate exoskeletons dissolve, making seawater alkaline; however, past lifeless leaves, raising the question of studies found that the surface waters are more alkaline than expected from plankton. why they keep dead weight that could Now scientists at the University of Exeter in England and their colleagues have deter- drain their productivity. To find out, mined that calcium carbonate “gut rocks,” first found in toadfish intestines about 20 scientists at the University of Buenos years ago, could account for a dramatic percentage of marine carbonate. Their com- Aires removed dead leaves from grass puter models estimate roughly 812 billion to two trillion kilograms of bony fish swim in the Argentine in the ocean, producing some 110 billion kilograms of calcium carbonate annually. The pampas, where amount constitutes at least 3 to 15 percent of the total ocean carbonate production and cattle graze. In possibly up to 45 percent. Increasing sea temperature and rising carbon dioxide this the absence of century could cause fish to produce even more calcium carbonate, the researchers sug- cows, the prun ing promoted gest in the January 16 Science. —Charles Q. Choi grass growth, but in the presence of bovines, STATISTICS CONSERVATION those grasses were grazed on more so than intact ones, resulting in less growth. The findings, published online Math against No Nets in January 15 by Oikos, suggest that dead leaves act as a defense against Profiling the Arctic herbivores. —Charles Q. Choi

Racial profiling makes little sense, mathematically Regulators may protect a fishery QUITTERS’ CASH speaking. Using statistical analyses, William Press before anyone even had a chance When the threat of lung cancer and of the University of Texas at Austin has found that to cast a net. Melting sea ice and wrinkles doesn’t work, maybe $750 will. choosing people to screen based on ethnicity is no the migration of salmon and oth- Cigarette smokers who received money to quit were 2.9 times more likely to more effective than random checks, because non- er fish farther north make the break the habit than those who just tried terrorists vastly outnumber terrorists. The optimal Arctic region attractive. Because to do it for their way to screen would be to use “square-root-biased of a lack of studies detailing the health. Participants sampling,” so that someone nine times as likely to impact of commercial fishing in were offered $100 to be a terrorist as the average traveler would be the area, the U.S. North Pacific complete a smoking cessation program, screened three times more frequently. This ap- Fishery Management Council— $250 for quitting with proach would turn up more terrorists in part by charged with administering Alas- in the first six months avoiding the repeated screening of the same inno- kan waters—voted unanimously and $400 for keeping clean an addition ) cent people who fit the profile. But because that on February 5 to close off to any al six months. Even after that, those who

got the cash were 2.6 times more likely cigarettes

strategy would be difficult to implement, Press says fishing all U.S. waters north of is ( to have stayed smoke-free. The study b that mathematically, the more sensible method is the Bering Strait—some 196,000 or appears in the February 11 New England ); C not to profile at all. The study appears in the Feb- square miles of ocean. Studies to Journal of Medicine. —Coco Ballantyne cows ruary 10 Proceedings of the National Academy of determine safe harvesting levels ( Sciences USA. —John Matson and the impact on indigenous WHEN ORBITS COLLIDE Getty Images people would be required before In an orbital traffic accident 490 miles CHECKED out: Profiling is no more any fishing could begin. The pro- above Siberia, a Russian satellite and a effective than random screening. posed prohibition does not mean commercial satellite owned by U.S. com munications firm Iridium collided in Feb that the entire Arctic is safe —sev-

ruary. It wasn’t exactly unexpected, giv E mmerich-We bb ); ); en other countries have claims en the number of objects in orbit—the there, including Norway, which past 20 years has seen three other acci has already begun fishing in its dents, but they were minor, only produc security guardsecurity waters. —David Biello ing a few pieces of debris. This latest ( impact, however, yielded hundreds, and some pieces have drifted down to the altitude of the International Space Sta Getty Images

tion, posing a small but still real hazard. errao

Read More ... S News Scan stories with this icon have extended coverage on —John Matson arlos

www.SciAm.com/apr2009 C

SciAm Perspectives Healthy Growth for U.S. Farms Congress and the FDA must upend the nation’s agricultural policies to keep its food supply safe

By The Editors

griculture has fueled the eruption of human civilization. imals must be given low doses of antibiotics to shield them from Efficiently raised, affordable crops and livestock feed the fetid conditions. The drug-resistant bacteria that emerge have A our growing population, and hunger has largely been now entered our food supply. The first study to investigate farm- banished from the developed world as a result. Yet there are rea- bred MRSA in the U.S.—amazingly, the Food and Drug Admin- sons to believe that we are beginning to lose control of our great istration has shown little interest in testing the nation’s livestock agricultural machine. The security of our food supply is at risk— for this disease—recently found that 49 percent of pigs and 45 in ways more noxious than anyone had feared. percent of pig workers in the survey harbored the bacteria. Un- The trouble starts with crops. Orange groves in Florida and fortunately, these infections can spread. According to a report California are falling to fast-moving blights with no known published in Emerging Infectious Diseases, MRSA from animals cure. Cavendish-variety bananas—the global standard, each is now thought to be responsible for more than 20 percent of all genetically identical to the next—will almost certainly be wiped human MRSA cases in the Netherlands. out by emerging infectious disease, just as the Cavendish’s pre- In April 2008 a high-profile commission of scientists, farm- decessor was six decades ago. And as entomologists Diana Cox- ers, doctors and veterinarians recommended that the FDA phase Foster and Dennis vanEngelsdorp describe in “Saving the out the nontherapeutic use of antibiotics in farm animal produc- Honeybee,” on page 24, a mysterious affliction has ravaged tion, to “preserve these drugs to treat sick animals, not healthy honeybee colonies around the U.S., jeopardizing an agricultural ones” in the words of former Kansas governor John Carlin, the system that is utterly dependent on farmed, traveling hives to commission’s chair. The FDA agreed and soon announced that it pollinate vast swaths of monoculture. The ailment may be in would ban the use of one widespread antibiotic except for strict- part the result of the stresses imposed on hives by this uniquely ly delineated medical purposes. But five days before the ban was modern system. set to take effect, the agency qui- Plants and animals are not the only ones getting sick, howev- etly reversed its position. Al- er. New evidence indicates that our agricultural practices are though no official reason was leading directly to the spread of human disease. given, the opposition of the Much has been made in recent years of MRSA, the antibiotic- powerful farm lobby is widely resistant strain of Staphylococcus bacteria, and for good reason. thought to have played a role. In 2005, the most recent year for which figures are avail- This is just one example of a able, about 95,000 MRSA infections caused the deaths food production system that protects of nearly 19,000 Americans. The disease first a narrow set of interests over the na- incubated in hospitals—the killer bacterium is tion’s public health. Simple measures an inevitable evolutionary response such as the reinstatement of the FDA’s to the widespread use of anti- initial ruling are necessary and im- biotics—but has since found portant steps. But Congress needs a home in locker rooms, to take a far more comprehensive prisons and child care fa- approach to realign the country’s cilities. Now the bacteria agricultural priorities with its health priorities, have spread to the farm. to eliminate subsidies that encourage factory Perhaps we should not be farming, and to encourage the growth of polyculture surprised. Modern factory and good old-fashioned crop rotation in the U.S. As the farms keep so many animals world is quickly learning, a civilization can only be as healthy

matt collins matt in such a small space that the an- as its food supply. ■

Sustainable Developments Needed: A Fiscal Framework Rather than arguing about the value of taxes or spending, economic planners need to take a systematic long view BY JEFFREY D. SACHS

The economic debate in the U.S. regarding the fiscal stimulus package centered on “bang for the buck,” that is, on whether tax cuts or spending increases would produce more jobs. This limited perspective is very misleading, however: the choice of spending versus taxes should turn first and foremost on the purposes of government, or what econ- omists quaintly call “the allocation of resources.” It’s silly to debate whether investing in a $100-million bridge creates more jobs than a $100 -million tax cut if we need the bridge! The Amer- ican Society of Civil Engineers has long documented the crum- bling state of U.S. infrastructure and the pressing need for $2.2 trillion in investments for our well-being and competitiveness. Government spending and taxation affect the distribution of income demographically and temporally. America ranks 22nd out of 23 high-income countries in public social outlays as a per- national debts. Less obviously, the huge budget deficits will crowd centage of national income (ahead only of Ireland) for health, out some private investment spending and exports as the econo- pensions, income support and other social services. Our politi- my recovers. Higher taxes needed to cover the service on that debt cal discourse tends to focus on the middle class and neglect the will not only squeeze consumption but may also distort the econ- poor, whereas our tax and spending policies often benefit the omy through disincentives on saving, work or other activities. wealthy. As a result, the U.S. has the largest poverty rate, income There is a sound method to combine the analytical perspec- inequality and per-capita prison population of any high-income tives of macroeconomic stimulus, resource allocation, income nation, as well as the worst health conditions. distribution, and generational equity and efficiency. It is called a The timing of tax cuts and spending increases also affects the medium-term fiscal framework, which systematically presents well-being of today’s generation versus future ones. The U.S. has the trade-offs of taxation and spending backed up by formal bud- a chronic fiscal deficit because federal taxation, at around 18 per- get projections for at least five to 10 years and in some budgetary cent of gross national product (GNP), is enough to cover only five processes more than 50 years. Norway, for instance, takes such types of federal programs: retirement and disability, medical a long view in the management of its hydrocarbon wealth. care, veterans’ programs, defense and homeland security, and in- Higher deficits to increase spending on urgently needed pub- terest on the public debt. All other federal outlays—for educa- lic goods such as infrastructure and on transfers to states and cit- att collins att tion, diplomacy and international assistance, public administra- ies to help them tackle the pressing needs of the poor and the un- M tion, science and technology, sustainable energy, water and sani- employed can combine desirable macroeconomic stimulus, effi- tation, roads, broadband, help for the poor—are in effect funded cient resource allocation and redistribution. Over time, we will by borrowing. The chronic deficit problem, now at least 5 per- almost surely have to raise taxes to close the deficits and to cover cent of GNP, will tend to get much worse as the population ages the long-term costs of government. Right now, however, it’s time and health care costs rise, until we finally choose to tax ourselves to think systematically about the long-term role of government adequately to pay for the government we need and want (and and how to pay for it in the coming years. ■ have committed to by law in many entitlements programs). Temporary deficits can boost the economy in a recession, al- Jeffrey D. Sachs is director of the Earth Institute at Columbia though temporary income tax cuts and rebates tend to be saved University (www.earth.columbia.edu). rather than spent. Prolonged deficit spending, however, would im- h by bruce gilbert/earth institute; illustration by by illustration institute; gilbert/earth bruce by h pose future burdens. The most obvious will be the need to service An extended version of this essay is available at p the public debts owed to China and other holders of treasury www.SciAm.com/apr2009

bills—the U.S. is on a path to multiply its already massive inter- Photogra

About 1.6 million people die of tuberculosis (TB) each year1 mostly in developing nations lacking access to fast, accurate testing technology. TB is the current focus of the Foundation for Innovative New Diagnostics (FIND), established with funding from the Bill and Melinda Gates Foundation. FIND is dedicated to the advancement of diagnostic testing for infectious diseases in developing countries. For more information, visit www.finddiagnostics.org.

A young girl reveals hope in India, which carries one-ﬁ fth of the global burden of TB.

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™ greatest needs. 1 Source of all statistics cited: The BD MGIT (Mycobacteria Growth Indicator StopTB/World Health Tube) system can shorten the recovery of TB in BD – Helping all people live healthy lives. Organization, 2007. 2 FORTUNE, March 2008 3 ® Ethisphere Magazine, June 2008 World TB Day Please visit www.bd.com March 24, 2009 BD, BD Logo and BD MGIT are trademarks of Becton, Dickinson and Company. © 2009 BD

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Pub: SCI AM, Marck 2009

Size: Bleed: 8.375 x 11 Trim: 8.125 x 10.75 OPINION

Skeptic Inside the Outliers Are successful people primarily the beneficiaries of luck, timing and cultural legacy? By Michael Shermer

What is the difference between Joe Six-Pack, Joe product of “the tradition of wet-rice agriculture” that must be the Plumber and Joe Biden? One is vice presi- practiced year-round and that requires “the highest emphasis on dent; the other two are not. Why? The answer effort and hard work,” and that’s why they study all summer depends on a host of interactive variables that while American students go to the mall. must be factored into any equation of success: Such prodigies and geniuses, Gladwell says, “are products of genes, parents, siblings, peers, mentors, prac- history and community, of opportunity and legacy. Their success tice, drive, culture, timing, legacy and luck. The rub for the scien- is not exceptional or mysterious. It is grounded in a web of ad- tist is determining the percentage of influence of each variable and vantages and inheritances, some deserved, some not, some its interactions, which requires sophisticated statistical models. earned, some just plain lucky—but all critical to making them Journalists unconstrained by research protocols churn out who they are.” self-help books that focus on select variables that interest them. Well, yes and no. As Frank J. Sulloway, author of the compre- Few do so better than Malcolm Gladwell, and in his new book hensive study of success Born to Rebel (Pantheon, 1996), told Outliers: The Story of Success (Little, Brown, 2008), the New me: “Creative people are not just sitting around waiting for op- Yorker writer claims that successful people are not “self-made” portunities to come to them. They create their own opportuni- but instead “are invariably the beneficiaries of hidden advantag- ties. Charles Darwin was already planning a voyage of discov- es and extraordinary opportunities and cultural legacies that al- ery to the Canary Islands, for example, when the position on the low them to learn and work hard and make sense of the world in Beagle opened up. If the Beatles hadn’t gone to Hamburg, they ways others cannot.” would have gotten their 10,000 hours somewhere else. What Bill Gates, for example, may be smart, but Gladwell prefers distinguishes Gates is that he has a really interesting creative to emphasize the fact that Gates’s wealthy parents sent him to a mind, and he would have had that mind even without a comput- private school that had a computer club with a teletype time- er terminal at his private school and hence would likely have sharing terminal with a direct link to a mainframe computer in found alternative ways to access programming tools.” And of Seattle, and in 1968 this was very unusual. His good fortune to course, Leopold Mozart’s son was a child prodigy and musical be born in the mid-1950s also meant that Gates genius, not merely the beneficiary of cultural legacy. came of age when the computer industry was Even the 10,000-hour rule isn’t just about skill mastery. Ac- poised to have someone of his experience start a cording to Dean Keith Simonton, author of Origins of Genius software company. (Oxford University Press, 1999), success includes a Darwinian Similarly, Gladwell says, Mozart’s father was a process of variation and selection. Creative geniuses generate a composer who mentored the young Wolfgang into massive variety of ideas from which they select only those most greatness from age six until his early 20s, when his likely to survive and reproduce. The best predictor of winning a compositions morphed from pleasantly melodious Nobel Prize in science, for example, is the rate of journal citation. into masterful. The Beatles’ lucky break came in As Simonton notes, “empirical studies have repeatedly shown that Hamburg, Germany, where they were able to log the single most powerful predictor of eminence within any cre- in more than 1,200 live performances and thereby ative domain is the sheer number of in- meet the well-known 10,000-hour rule for per- fluential products an individual has giv- fecting a profession. Elite hockey players are dis- en the world.” proportionately born in January, February and Genius is as ge- March (40 percent compared with the expected nius does. ■ birthrate, which in most studies hovers around 25 percent) because the birthday cutoff date when Michael Shermer they were youngsters first hitting the ice was Janu- is publisher of h by brad swonetz; illustration by matt collins ary 1, and players born early in the year were Skeptic magazine p slightly bigger, stronger and faster, giving them an (www.skeptic.com) and

advantage. Asian student wunderkinds are the author of The Mind of the Market. Photogra

Anti Gravity Boobs at Work Unacceptable ways to waste time on the job BY STEVE MIRSKY

The Internet is indeed a wonder of our age. Why, workplace, his heart must have pounded. When he reached the just last night, while watching the DVD of mention of the $58,000, his pulse no doubt shot up and he might Inherit the Wind (it’s Darwin’s bicentennial have softly moaned. Then he and the NSF semiannual report be- birthday week as I write), I was able to simul- came one. And his outrage exploded like a volcano that could taskically discover that Fredric March and no longer contain the roiling molten lava within. “The semian- Florence Eldridge, who play Matthew and Sar- nual report,” Grassley said in a press release, “raises real ques- ah Brady, were married in real life and often performed together tions about how the National Science Foundation manages its in movies and on stage. (Inherit the Wind, by the way, is actu- resources, and Congress ought to demand a full accounting be- ally a bombastically bad movie. But it’s fun.) My research was fore it gives the agency another $3 billion in the stimulus bill.” over before Matthew, a character based on William Jennings Grassley then joined with Senators Barbara Mikulski of Bryan, could finish one of his long-winded speeches. Maryland and Richard Shelby of Alabama to share their indig- Of course, easy access to such tantalizing data has the poten- nation at the waste of the taxpayers’ money. (Again, the porn ad- tial for misuse. Which clearly was the case at the National Sci- dict was already gone, despite the fact that a federally funded ence Foundation (NSF), where an employee spent a significant worker who loses only $58,000 in this economy should probably amount of time at work perusing pornography. At least that’s be nominated for employee of the month.) The three senators in- the official report—if he claimed he was investigating grant ap- troduced an amendment to the roughly $800-billion stimulus bill plications from researchers investigating human reproduction, that would freeze $3 million in operating funds for the NSF un- well, it didn’t fly. less the foundation took further steps to ensure that no pornog- The incident, and some other porn-related surfing by a hand- raphy ever sullied its computer screens again. ful of other NSF employees, was revealed in the foun- Much of this information came to me from a source dation’s semiannual report issued by its inspector gen- at the Senate Finance Committee, of which Grassley is eral. The primary porn culprit lost his job based on the ranking member. I made repeated requests of the the misuse of time and resources that was estimated source to assure me that the senatorial threats against to have wasted some $58,000. And the founda- the NSF would not cost any scientists their funding. tion installed filters, just as countless other The answers were inconclusive and then stopped employers in the U.S. have done when faced altogether. While this tempest in a D-cup made with exactly this same kind of abuse of com- news, the former NSF employee was joined by pany resources. NSF employees looking for 598,000 other Americans who lost their jobs in dirty pictures will henceforth have to be January. content with medical journals. Meanwhile the senators, who dithered for With the audit having been published, weeks over the stimulus bill, still have in their the NSF got back to work supporting and company their esteemed Louisiana colleague promoting scientific research. That is un- David Vitter, a known client of an infamous til Iowa senator Charles Grassley noticed Washington brothel. Vitter—who faces the foundation’s report. The waste wasn’t an election challenge from a porn star just playing computer solitaire or Freecell, or named Stormy Daniels—once tried to instant-messaging friends or searching the In- waste $100,000 in a federal funding ear- ternet for movie trivia. This was porn. mark for the Louisiana Fam- At first, Grassley was mildly in- ily Forum. That organiza- trigued. Perhaps he gently caressed tion campaigns against the the hard copy of the internal audit, teaching of evolution. So that h by flynn larsen; illustration by matt collins p its creamy white pages glistening under the in the future we can have gentle light of a desk lamp. As the senator read about a gov- new and better versions of

Photogra ernment-funded employee viewing lascivious images in the Inherit the Wind. ■

www.SciAm.com © 2009 SCIENTIFIC AMERICAN, INC. SCIENTIFIC AMERICAN 23 24 e f i l ■ ■ ■ KEY CONCEPTS ■ ■ ■ The The mysterious ailment called colony collapse disorder has wiped out tical tical solutions. could lead to pharmaceu drugs antiviral into search re And prevention. aid hive hygiene seems to to viruses. es, make bees vulnerable including farming practic factors, of combinations which in disease complex that require pollination. crops 100 nearly risk at putting disappear, ously out as honeybees mysteri emptied have worldwide Taking extra care with with care extra Taking a to pointing is Research beehives of Millions S c are emerging are emerging

ient ciece enc i sc The The causes turn out to be surprisingly complex, but solutions ifi large numbers of the bees that pollinate a third of our crops. e Hon — Saving the c The The Editors Am e ri can -

- - - • By Diana Cox-Foster and Dennis vanEngelsdorp D named it colony collapse disorder, or CCD. Cu CCD. or disorder, collapse colony it named the phenomenonhad described 2006 and later terdisciplinary working team that by December the mysterious disappearance. for explanation an seeking us called he when said Hackenberg town,” ghost a like was “It devoid ofBut no bees. were dead bees in sight. completely were hives 3,000 the of half More than healthy. seemed and remained queen the and workers young the of only and workers, numbers large lost had colonies maining re the of Many horrified. was he later, month a back came he when But it. put he as bees, with over” “boiling were colonies the nators, polli his on checked Hackenberg When flow. nectar needle Spanish Floridian of the last the catch tonow were and fields pumpkin vanian Pennsyl blooming on duties pollination their finished just had insects The Florida. central in locale winter their to home summer vania his and Pennsyl from his with family bees central their migrated Hackenberg 2006 of fall nia almonds. sylvania apples, Maine blueberries and Califor Penn melons, Florida as diverse as crops nate field field to from polli to beehives his trucks We and soon other formed researchers an in the in 42 years, past for the done he has As and often coast to coast, Hackenberg Hackenberg coast, to coast often and honeybees. Up and down the East Coast moving a living makes ave Hackenberg © 2009 SCIENTIFIC AMERICAN, INC. AMERICAN, © SCIENTIFIC 2009 y ------bee been identified. Bees suffering from CCD tend tend from CCD suffering Bees identified. been has culprit single no But factors. contributing tential causes for CCD and found many possible is and enough mild there are flowers tovisit. most any time of the year, wherever the weather mellifera Only fill. cannot bats and bees wild as such pe short for pollinators other that role a activity year, the of riods pollination intense require in Western countries. Large, monoculture farms era honeybee, European on the pends de production agricultural world’s the of third too. winter, this keepers say they have seen bee some their but yet, colonies available not collapse are data recent Canada, China, Europe and other regions. More large losses also surfaced from Australia, Brazil, hitting 36 percent of U.S. beekeepers. Reports of next winter the resumed die-off and expanded, The died. had colonies all of percent 30 than more that and losses similar suffered had ers beekeep U.S. of fourth a that revealed 2007 of And a survey our team conducted in the spring tion, it apparentbecame that he was not alone. spoke the around Hackenberg na to colleagues As survived. had colonies 3,000 original his of 800 only time but by that spring, following riously, Hackenberg’s colonies stopped dying the Our collaboration has ruled out many po outmany ruled has collaboration Our one because alarms raised has loss bee The — the kind universally adopted by beekeepers can deploy armies of pollinators at al at pollinators of armies deploy can Apis mellif Apis April 2009

A. A. ------

Charles Krebs www.SciAm.com © 2009 SCIENTIFIC AMERICAN, INC. SCIENTIFIC AMERICAN 25 and vegetables we consume routinely today— such as apples, blueberries, broccoli and almonds—could become the food of kings.

Silent Bloom When Hackenberg initially told us of his vanishing bees, our first thought was varroa mites. These aggressive parasites were largely responsible for a 45 percent drop in the number of managed bee colonies worldwide between 1987 (when they were first introduced in the U.S.) and 2006. Mature varroa females feed on hemolymph, the bees’ blood. The mites also carry viruses and actively inhibit the hosts’ immune responses. Hackenberg, like most expert beekeepers, already had long experience fighting mites, and he was adamant that, this time, the symptoms were different. One of us (vanEngelsdorp) performed autop- sies on Hackenberg’s remaining insects and found symptoms never observed before, such as scar tissue in the internal organs. Initial tests also detected some of the usual suspects in bee disease. In the gut contents we found spores of nosema, single-celled fungal parasites that can cause bee dysentery. The spore counts in these and in subsequent samples, however, were not high enough to explain the losses. Molecular analysis of Hackenberg’s bees, performed by the other of DAVE HACKENBERG was the first to be infested with multiple pathogens, includ- us (Cox-Foster), also revealed surprising levels of beekeeper to alert U.S. ento- ing a newly discovered virus, but these infec- viral infections of various known types. But no mologists to the inexplicable tions seem secondary or opportunistic—much single pathogen found in the insects could ex- disappearance of worker bees, the way pneumonia kills a patient with AIDS. plain the scale of the disappearance. a sign of what is now known The picture now emerging is of a complex con- In other words, the bees were all sick, but as colony collapse disorder, in dition that can be triggered by different combi- each colony seemed to suffer from a different the fall of 2006. By the end of nations of causes. There may be no easy remedy combination of diseases. We hypothesized that the winter, more than 60 per- to CCD. It may require taking better care of the something had compromised the bees’ immune cent of his 3,000-odd colonies were dead; nationwide the loss environment and making long-term changes to system, making them susceptible to any number was 30 percent. our beekeeping and agricultural practices. of infections that healthy colonies would nor- Even before colony collapse, honeybees had mally fend off. And Hackenberg was right: the suffered from a number of ailments that re- prime suspects, varroa mites, were not present duced their populations. The number of man- in numbers significant enough to explain the aged honeybee colonies in 2006 was about 2.4 sudden die-off. million, less than half what it was in 1949. But In the spring of 2007 our task force began de- The bees were beekeepers could not recall seeing such dramat- tailed, countrywide surveys of all aspects of col- all sick, but ic winter losses as occurred in 2007 and 2008. ony management, interviewing operators who Although CCD probably will not cause honey- had encountered CCD as well as those who had each colony bees to go extinct, it could push many beekeep- not. These and subsequent investigations ruled seemed to ers out of business. If beekeepers’ skills and out several potential causes. No single beekeep- know-how become a rarity as a result, then ing management method could be blamed. Large suffer from even if CCD is eventually overcome, nearly 100 commercial beekeepers were as likely to suffer a different of our crops could be left without pollinators — from high losses as were small operations or and large-scale production of certain crops hobbyists. The symptoms affected stationary combination could become impossible. We would still have beekeepers as well as migratory ones. Even some ELLE N VID Y VID A of diseases. corn, wheat, potatoes and rice. But many fruits organic beekeepers were affected. D

26 Scientific American © 2009 SCIENTIFIC AMERICAN, INC. April 2009 As media reports of the die-offs surfaced, the leaf-eating pests—and is more toxic to insects [The Authors] public also started expressing concern. Many than it is to vertebrates. But neonicotinoids also were eager to share their ideas as to the underly- enter the pollen and nectar of the plant—not just ing cause. Some of these proposals—such as the leaves—thus potentially affecting pollina- blaming CCD on radiation from cell phones— tors. Previous research had demonstrated that originated from poorly designed studies. Other neonicotinoids decrease honeybees’ ability to hypotheses were untestable at best, such as claims remember how to get back to their hive, a sign that the bees were being abducted by aliens. that they could be a contributor to CCD. One theory favored by many concerned citi- We and other experts also suspected that the Diana Cox-Foster is professor of zens was that bees could have been poisoned by bees’ natural defenses might be undermined by entomology at Pennsylvania State University and co-director of the pollen from genetically modified crops, specifi- poor nutrition. Honeybees—and wild pollina- colony collapse disorder working cally the so-called Bt crops. Bt crops contain a tors, too—no longer have the same number or team, made up of experts from gene for an insecticidal toxin produced by the variety of flowers available to them because we government and academia. Her bacterium Bacillus thuringiensis. When pest humans have tried to “neaten” our environ- research focuses on host-pathogen caterpillars feed on crops producing these tox- ments. We have, for example, planted huge ex- interactions. Cox-Foster traces her affinity for honeybees back ins, they die. But already before the onset of panses of crops without weedy, flower-filled bor- to her great-grandmother, who CCD, research had shown that the Bt toxin be- ders or fencerows. We maintain large green lawns was a commercial beekeeper in comes activated only in the guts of caterpillars, free of any “weeds” such as clover or dandelions. Colorado in the early 1900s. mosquitoes and some beetles. The digestive Even our roadsides and parks reflect our desire Dennis vanEngelsdorp’s passion tracts of honeybees and of many other insects to keep things neat and weed-free. But to bees for bees began in an undergraduate beekeeping course at the do not allow Bt to work. and other pollinators, green lawns look like des- University of Guelph in Ontario. It ., S Another popular theory, and a more credible erts. The diets of honeybees that pollinate large U. has carried him through several HE one, blamed synthetic poisons. The two main acreages of one crop may lack important nutri- appointments on West Indian IN T suspects were acaricides —chemicals beekeepers ents, compared with those of pollinators that feed projects and to his current dual SSES

O position as acting state apiarist for L use to keep mites in check—and pesticides, ei- from multiple sources, as would be typical of the the Commonwealth of Pennsylvania ONY

L ther in the environment or in the very field crops natural environment. Beekeepers have attempted and senior extension associate with CO the bees were pollinating. By 2006 newer types to manage these concerns by developing protein

BEE the entomology department at Y E of pesticides had replaced older varieties. One supplements to feed colonies—although the sup- Penn State. ON H type in particular, the neonicotinoids, had been plements have not on their own prevented CCD. Y OFY E

V blamed by beekeepers in France and elsewhere R U ) S for harming insect pollinators. This class of in- All-Out Effort A map : “ : E

C secticides mimics the effects of nicotine —a nat- Our task force focused its investigation on these R 2008 ( OU

S ural defense that tobacco plants deploy against two broad areas—pesticides and nutrition—in BER N, M SE E N C A E

TI [THE Extent of colony loss] S I HR 4071; D E N C N E LE A countrywide scourge );J TIC Colony collapse disorder Number of 12, AR

E (CCD) returned for a second Cox-Foster U honeybee colonies SS year in the winter of 2007–08. 28% ON ( 26% S . 3, I N estimated to have L H A survey of beekeepers in the 34% 19% VO died in the U.S. N JO spring of 2008 asked how 52% 56% many colonies failed to make 27% over the winter of 39% 15% 2007–08: Y OF ELLE PLOS ONE, PLOS it through that winter. 42% ES

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vanEngelsdorp 35% N percent of those losses were 27% 42% A Some beekeepers attributed to CCD. Most

Y D. V D. Y 32% reported B IMOWICZ ( states for which enough data losing up to were available were severely Colony loss (winter 2007–08) 40%

N HARAS hit. Large losses were also

ING2008,” Fewer losses than normal (<15%) R P S reported in Australia, Brazil, Normal (15%–25%) 90% Y OF ELLE Canada, China and Europe. More losses than normal (>25%) ES

T of their colonies.

R Insufficient data ALL2007TO F COU

www.SciAm.com © 2009 SCIENTIFIC AMERICAN, INC. SCIENTIFIC AMERICAN 27 WITHOUT HONEYBEES, many foods addition to the other obvious possibility, that a compounds, and some contained as many as 35. included in the breakfast at new or newly mutated pathogen could be caus- But although both the levels and the diversity of the left would become too rare ing CCD. Tests of our three hypotheses required chemicals are of concern, none is likely to be the for most people to afford. collecting samples—lots of samples. We joined sole smoking gun behind CCD: healthy colonies Shortages would affect an array Jeff Pettis of the U.S. Department of Agriculture sometimes have higher levels of some chemicals of fruits, as well as jams and lab in Beltsville, Md., to conduct this monumen- than colonies suffering from CCD. jellies, almonds and even milk, tal effort that involved long days, lots of miles No neonicotinoids were found in the original because dairies use alfalfa on the road and the challenge of collecting samples. But these or other pesticides cannot yet (which needs pollinators) as a protein-rich feed for dairy cows. enough material to share with the entire team. be exonerated. Honeybee colonies are dynamic, With no dead bees to study, we decided to col- and our initial sampling was not—we took sam- lect live bees from apiaries in the midst of col- ples only once. It remains possible, if not likely, lapse, based on the premise that survivors would that bees afflicted by CCD were harmed by a harbor the disease in its early stages. Bees were chemical or mixture of chemicals not evident at collected in alcohol for varroa and nosema the time we collected samples. counts. Bees, pollen and honeycomb wax were Our attempts to identify a new infectious frozen on dry ice and rapidly shipped back to disease—or a new strain of an old one—that labs in Pennsylvania or Maryland to be stored could be at the root of CCD initially looked as fast facts in ultracold freezers and preserved for molecu- if they would go nowhere fast. None of the lar and chemical analyses. known bacterial, fungal or viral diseases of bees ■■ There are an estimated 900 Some samples were sent to our colleague Da- could account for the CCD losses, so we had no to 1,000 commercial beekeepers vid Tarpy of North Carolina State University, clue what to look for. in the U.S., managing 2.4 million colonies. who measured protein content. Tarpy found no Then Cox-Foster, with Ian Lipkin’s group at notable difference between apiaries that had Columbia University (and with help from bio- ■■ Nearly 100 kinds of crops require CCD and others that were seemingly healthy. tech company 454 Life Sciences in Branford, pollination by honeybees. The His results suggested that nutritional state—on Conn.), turned to a sophisticated microbe- annual value of bees’ work its own—could not explain CCD. hunting method called metagenomics. In this is $14 billion in the U.S. and Much more startling was the outcome of our technique, nucleic acids (DNA and RNA) are $215 billion worldwide. team’s search for pesticides, for which we enlist- collected from an environment containing

■■ Every February virtually all moved the help of Pennsylvania State University re- many different organisms. The genetic mate- able U.S. hives are taken to Cali- searchers Maryann Frazier, Jim Frazier and rial is all blended together and minced into fornia to pollinate almond trees. Chris Mullin and of Roger Simonds, a chemist pieces short enough that their sequences of at the USDA lab in Gastonia, N.C. (By coinci- code “letters” can be deciphered. In ordinary ■■ Even before CCD, in certain regions dence, Simonds happens to be a beekeeper him- gene sequencing, researchers would then use n of China bees had completely a self.) His broad-spectrum analysis, sensitive to computer software to put the pieces back to- ic disappeared, possibly because er Am of pesticide use, forcing orchard insecticides, herbicides and fungicides, found gether and reconstruct the genome of the orig- more than 170 different chemicals. Most stored- inal organism. But in metagenomics, the genes

owners to pollinate pear trees ntific e

by hand. pollen samples contained five or more different belong to different organisms, and so sequenc- Sci

DERRICK DITCHBURN www.dereilanatureinn.ca time.) The other strain probably showed up ear up showed probably strain other The time.) vent a critical shortage of pollinators at blossom to pre ban the lobbied to lift industry almond (The 1922. since effect in been had that tion importa honeybee on ban a lifted government theU.S. after in2005 frominAustralia flown colonies in arrived likely most strains the of and that two of them infect bees in the U.S. One of atexist strains the different virus least three From subsequent work on IAPV, we know that Case Closed? infection. IAPV to ble vulnera exceptionally bees the made just have could CCD example, For disease. the caused IAPV that proof not was correlation such strong But CCD. from suffering not was that with CCD symptoms and in only one operation all almost in found lytic seizures. In our initial sampling, IAPV was fort to find outwhy bees withwere para dying ef an of course the in Jerusalem of University Hebrew the of Sela Ilan by 2004 in described first was pathogen This IAPV. or virus, ralysis pa acute Israeli the theU.S.: in identified been di and bee viruses. several other fungi in aiding as such gestion. biology We bee also found in two nosema role species, two essential bacteria may be symbionts, perhapsan serving world. strongly These thatsuggest findings those in two previous from studies of other parts the described been had that bacteria different eight showed that all samples (CCD and healthy) had it First, honeybees. of knowledge general our potential culprits. viruses and sites of organisms analysis molecular in expertise with searchers Re organisms. known to belonging sequences Nonbee sequences sequenced. were then been matched just to genetic had genome honeybee were easy to filter out fortunately,because, the those But themselves. bees the from were ples biosis) or as sym infections. (in collaborators as either living ganism, or de larger a by to hosted applied be microorganisms also tecting can it But croorganisms. and soil, a revealing diversity of surprising mi seawater as such environments to survey used ones, in has an Metagenomics been ecosystem. of collection including microscopic organisms, a in sequences the of snapshot a produces ing www.SciAm.com But one bee virus stood out, as it as out, never had stood virus one But bee The sam our in sequences gene most Naturally, CSI- style investigation greatly expanded — including bacteria, fungi, para fungi, bacteria, including —

joined our team to identify identify to team our joined — though not all not though — colonies colonies ------© 2009 SCIENTIFIC AMERICAN, INC. AMERICAN, © SCIENTIFIC 2009 lier lier and is quite different. Where that one came seemed to support the notion that IAPV can can IAPV that notion the support to seemed findings those So CCD. in expect would one just were as hives, the notbees near The dying twitching with paralytic seizures on the ground. or two weeks of exposure, the bees began to die, mimicked some symptoms of CCD. Within one infection the enough, Sure IAPV. with laden water sugary insects the into fed and bees greenhouses with filled hives placed team Her bees that had no previous exposure to honey the virus. healthy with experimented Cox-Foster rapidly.changing possibly and develop strains different while, a many for into ing world the of parts other in The bees. of pests data also has suggest that existed in IAPV bees introduced newly on country the into hitchhiked have may it or plement, bees secrete to feed their larvae) or a pollen sup by way ofof importation royal jelly (a nutrient from it is unknown; may have been introduced H “That was can nectar. grow and says. a provide real landmark,” Berenbaum wildflowers land where aside such conservation as setting measures, protection pollination identify seen. were researchers they where where of sites, note Web the take to and them species submit and pollinators of pictures take warned. collaborations Several call report Web-based on help. citizen-scientists’ Volunteers worldwide), and not much is known about the state of health for most of them, the NRC routes. migration their along flowers find can the animals where of corridors,” “nectar are the preservation urging and biologists Mexico, extinction of risk at are bats habitats. and loss of wetland forest prairie, with consequent 1960 and 1940 between there disappeared species and Illinois from data that found four bumblebee he says. in crops other greenhouses, to assist in and of have the imported tomatoes that pollination U.S. farmers bumblebees European from may The Davis. fungus have to bumblebees spread the California, western fungus microorganism, according to work by entomologist Robbin Thorp of the University of by off killed probably to Columbia, British California central University of Illinois. impoverished habitats, says the study’s lead author, entomologist May Berenbaum hum of the and bats also and poisoning to pesticide but CCD, vulnerable diseases, such make as honeybees introduced insects some including that afflictions some of from may the same man-made be species These suffering mingbirds. pollinators, wild American North of species Too Ailing, Are Pollinators Wild In In an effort to settle the issue of role, IAPV’s In 2008 the U.S. Congress for the first time modified its agricultural policy to include topolicy include itsagricultural for time modified the In first the U.S. Congress 2008 exist 200,000 estimated (an species pollinator many so only monitor can biologists But hummingbirds and bats pollinating of species few a in Declines in the A published January study more recent The western bumblebee, for example, has disappeared from a region stretching from A National Research Council (NRC) report in 2006 pointed to downhill trends in certain in to trends certain in pointed downhill 2006 report (NRC) Council A Research National in years. drops recent population are to not have the only pollinators oneybees suffered — a period that coincided with large-scale agricultural intensification in the state, in the state, intensification agricultural with large-scale a that coincided period — might relate to habitat changes. Many of them overwinter in Many of to might changes. them relate overwinter habitat Biological Conservation Conservation Biological - - - — Davide Castelvecchi, staff writer Davide Castelvecchi, deserts. look like green lawns pollin and other To bees SC Nosema bombi, Nosema bombi, IENT — IFI to to the point that some ators, ators, C AM looked at historical looked at historical

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[THe search for the cause] Many Suspects, No Convictions Yet

Researchers have SUSPECT: CHEMICALS looked into virtually As many as 170 different all aspects of honeybee synthetic chemicals have life in search of the culprit been found in beehives of both sick and healthy behind colony collapse. The colonies, with some work has exonerated some suspects samples of pollen stored and has pointed to possible combi- in cells containing as many as 35 types. Al- nations of factors that can cause though no single chemical or contribute to CCD. seems to be the cause of CCD, pesticides may weaken bees’ health.

SUSPECT: varroa mites This mite, seen below sucking blood from a pupa (an inter- mediate stage between larva and adult), is the honeybee’s most common and destructive pest. But collapsing colonies did not have significant mite infestations.

SUSPECT: PARASITES Some of the bees in collapsing colonies were infected by single-celled fungi, such as Nosema apis (below), which invades the intestinal tract and causes dysentery. But levels of infection were too low to be lethal on their own.

SUSPECT: Israeli acute paralysiS virus IAVP has been shown to produce symptoms similar to CCD’s and has occurred in most affected colonies that have been examined. It could be the cause of the disorder or a complication that is the ultimate cause of death.

30 Scientific American © 2009 SCIENTIFIC AMERICAN, INC. April 2009 [One potential solution] More Ways a bee medicine? to fight back A Miami-based biotechnology start-up company called Beeologics is developing an antiviral drug that ex- Restoring a balance to the habitat ploits an ancient immune mechanism called RNA interference. Cells in most animals and plants use short- of pollinators might improve their interfering RNA (siRNA) segments to inhibit the formation of viral proteins; here siRNA designed to target general well-being and help prevent IAPV would be fed to colonies as part of double-stranded RNA mixed into a syrup. colony collapse. Large stretches of single crops or residential lawns could without treatment, virus spreads with treatment, virus is stopped be broken up with more “weedy” meadows and hedgerows. Plants ●1 IAPV enters bee cell. 1 RNA designed to match Virus ● flowering at different times of the genetic sequences from year could then provide more variety Bee cell the virus is fed to the bee and enters the cell. in pollinators’ diets and support them ●2 The cell’s enzymes year-round. chop the synthetic RNA 2 Viral RNA Sterilizing used beehives with ● into siRNA segments. is released. ●3 The cell’s DNA-destroying gamma rays before ribosomes reusing them for a new colony cuts translate Silencing Viral RNA complex down the risk of CCD recurrence, RNA into Drug siRNA possibly because it kills microorgan- viral proteins. isms that contribute to the disease. 3 ● The siRNA com- Research on the impact of pesti- 4 Viral proteins bines with cellular ● cides on pollinators usually focuses on allow the virus Ribosome enzymes into a Viral protein No viral silencing complex. possible lethal effects. More research to reproduce, proteins sickening the host is needed on whether certain pesti- and spreading ●4 The silencing complex locks onto matching cides can put insects under stress, to other bees. viral RNA and blocks translation. even if the chemicals do not kill them outright. cause CCD or at least contribute to the problem. ate the kind of protection against specific agents Additional sampling efforts by several groups that vaccines induce in humans and other mam- showed, however, that IAPV was widespread in mals. But researchers are beginning to pursue the U.S. and that not all infected colonies had other approaches, such as one based on the new

); symptoms of CCD, implying either that IAPV technique of RNA interference [see box above],

alone cannot cause the disease or that some bees which blocks a virus from reproducing inside a .); are predisposed to be IAPV-resistant. In partic- bee’s cells. A longer-term solution will be to ular, a joint study the two of us initiated in 2007 identify and breed virus-resistant honeybees. Nosema sp ( varroa mite on larva ( with the USDA has tracked colonies owned by Such an effort could take years, though, per- three traveling beekeepers and has observed col- haps too many to avoid having a large number onies that were infected with I A PV without col- of beekeepers go out of business. ) lapsing. Some of those colonies have later been Meanwhile many beekeepers have had some ➥ More To

Photo Researchers, Inc. able to rid themselves of the virus. success at preventing colony loss by redoubling

Y Explore illustrations R ( n TO USDA BeeUSDAResearch Laboratory The growing consensus among researchers their efforts at improving their colonies’ diets, se

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ti Nelson C. Lau and David P. Bartel s LAB i E

Smit and exposure to pesticides— can interact to and nosema in check, and practicing good hy- hr in Scientific American,Vol. 289, No. 2, NC c E ON n t CI weaken colonies and make them susceptible to giene. In particular, research has shown that pages 26–33; August 2003. S ar e: Je B g

RAL a virus-mediated collapse. In the case of our ex- sterilizing old beehive frames with gamma rays a of y s p Status of Pollinators in North i h es periments in greenhouses, the stress of being before reusing them cuts down the risk of colo- t ); CeNT); t

r America. National Research Council. nd ou confined to a relatively small space could have ny collapse. And simple changes in agricultural National Academies Press, 2007. e a ); C ); g

a been enough to make colonies succumb to practices such as breaking up monocultures varroa mite varroa e p (

it IAPV and die with CCD-like symptoms. More with hedgerows could help restore balance in Decline of Bumble Bees (Bombus) s recent results from long-term monitoring have honeybees’ diets, while providing nourishment in the North American Midwest. bee with pollen ); oppo ( identified other unexpected factors for in- to wild pollinators as well. Jennifer C. Grixti, Lisa T. Wong, Sydney A. Cameron and Colin Favret creased colony loss, including the fungicide Humankind needs to act quickly to ensure in Biological Conservation, Vol. 142,

Photo Researchers, Inc. chlorothalonil. Research is now focused on un- that the ancient pact between flowers and pol- D No. 1, pages 75–84; January 2009. Minden Pictures Minden RE Y h

S derstanding how these factors relate to colony linators stays intact, to safeguard our food sup- oc W The Mid-Atlantic Apiculture Research RE

K n collapse. ply and to protect our environment for genera- Israeli acute paralysis virus e ( g and Extension Consortium: n r A vaccine or cure for bee viruses and IAPV tions to come. These efforts will ensure that u se e: aNDe: n g http://maarec.cas.psu.edu s-J a a n p

ti specifically would be desirable. Unfortunately, bees continue to provide pollination and that a s e i H it s hr vaccines will not work on honeybees, because our diets remain rich in the fruits and vegetables The Xerces Society for Invertebrate c idi& n e e H oppo j the invertebrate immune system does not gener- we now take for granted. ■ Conservation: www.xerces.org

www.SciAm.com © 2009 SCIENTIFIC AMERICAN, INC. SCIENTIFIC AMERICAN 31 c o s m o l o g y Does dark energy Maybe not. Really Exist? The observations that led astronomers to deduce its existence could have another explanation: that our galaxy lies at the center of a giant cosmic void By Timothy Clifton and Pedro G. Ferreira

n science, the grandest revolutions are often of a universe populated by billions of galaxies triggered by the smallest discrepancies. In the that stretch out to our cosmic horizon, we are led I16th century, based on what struck many of to believe that there is nothing special or unique his contemporaries as the esoteric minutiae of ce- about our location. But what is the evidence for Key Concepts lestial motions, Copernicus suggested that Earth this cosmic humility? And how would we be able ■ ■ The universe appears to be was not, in fact, at the center of the universe. In to tell if we were in a special place? Astronomers expanding at an accelerat- our own era, another revolution began to unfold typically gloss over these questions, assuming ing rate, implying the exis- 11 years ago with the discovery of the accelerat- our own typicality sufficiently obvious to war- tence of a strange new ing universe. A tiny deviation in the brightness of rant no further discussion. To entertain the no- form of energy—dark ener- exploding stars led astronomers to conclude that tion that we may, in fact, have a special location gy. The problem: no one is they had no idea what 70 percent of the cosmos in the universe is, for many, unthinkable. Never- sure what dark energy is. consists of. All they could tell was that space is theless, that is exactly what some small groups of ■ ■ Cosmologists may not ac- filled with a substance unlike any other—one physicists around the world have recently been tually need to invoke exotic that pushes along the expansion of the universe considering. forms of energy. If we live rather than holding it back. This substance be- Ironically, assuming ourselves to be insignifi- in an emptier-than-average came known as dark energy. cant has granted cosmologists great explanatory region of space, then the It is now over a decade later, and the existence power. It has allowed us to extrapolate from cosmic expansion rate varies with position, of dark energy is still so puzzling that some cos- what we see in our own cosmic neighborhood to which could be mistaken mologists are revisiting the fundamental postu- the universe at large. Huge efforts have been for a variation in time, lates that led them to deduce its existence in the made in constructing state-of-the-art models of or acceleration. first place. One of these is the product of that the universe based on the cosmological princi- earlier revolution: the Copernican principle, that ple—a generalization of the Copernican principle ■ ■ A giant void strikes most cosmologists as highly un- Earth is not in a central or otherwise special po- that states that at any moment in time all points likely but so for that matter sition in the universe. If we discard this basic and directions in space look the same. Combined does dark energy. Observa- principle, a surprisingly different picture of what with our modern understanding of space, time tions over the coming years could account for the observations emerges. and matter, the cosmological principle implies will differentiate between Most of us are very familiar with the idea that that space is expanding, that the universe is get- the two possibilities. our planet is nothing more than a tiny speck or- ting cooler and that it is populated by relics from —The Editors biting a typical star, somewhere near the edge of its hot beginning—predictions that are all borne

an otherwise unnoteworthy galaxy. In the midst out by observations. dixon don

32 Scientific American © 2009 SCIENTIFIC AMERICAN, INC. April 2009 uneven expansion of space, caused by variations in the density of matter on an epic scale, could produce the effects that astronomers conventionally attribute to dark energy.

You are here

www.SciAm.com © 2009 SCIENTIFIC AMERICAN, INC. SCIENTIFIC AMERICAN 33 Astronomers find, for example, that the light where, we are led to the conclusion that the uni- from distant galaxies is redder than that of near- verse must be permeated by an exotic form of en- by galaxies. This phenomenon, known as red- ergy, dark energy, that exerts a repulsive force. shift, is neatly explained as a stretching of light Nothing meeting the description of dark en- waves by the expansion of space. Also, micro- ergy appears in physicists’ Standard Model of wave detectors reveal an almost perfectly smooth fundamental particles and forces. It is a sub- curtain of radiation emanating from very early stance that has not as yet been measured directly, times: the cosmic microwave background, a relic has properties unlike anything we have ever seen of the primordial fireball. It is fair to say that and has an energy density some 10120 times less these successes are in part a result of our own hu- than we may have naively expected. Physicists mility—the less we assume about our own signif- have ideas for what it might be, but they remain icance, the more we can say about the universe. speculative [see “The Quintessential Universe,” by Jeremiah P. Ostriker and Paul J. Steinhardt; Darkness Closes In Scientific American, January 2001]. In short, So why rock the boat? If the cosmological prin- we are very much in the dark about dark energy. ciple is so successful, why should we question it? Researchers are working on a number of ambi- The trouble is that recent astronomical observa- tious and expensive ground- and space-based tions have been producing some very strange missions to find and characterize dark energy, results. Over the past decade astronomers have whatever it may be. To many, it is the greatest found that for a given redshift, distant superno- challenge facing modern cosmology. va explosions look dimmer than expected. Red- shift measures the amount that space has A Lighter Alternative expanded. By measuring how much the light Confronted with something so strange and from distant supernovae has redshifted, cosmol- seemingly so improbable, some researchers are ogists can then infer how much smaller the uni- revisiting the reasoning that led them to it. One verse was at the time of the explosion as com- of the primary assumptions they are questioning pared with its size today. The larger the redshift, is whether we live in a representative part of the the smaller the universe was when the supernova universe. Could the evidence for dark energy be copernicus’s occurred and hence the more the universe has accounted for in other ways if we were to do legacy expanded between then and now. away with the cosmological principle? The observed brightness of a supernova pro- In the conventional picture, we talk about the The Copernican principle holds that vides a measure of its distance from us, which in expansion of the universe on the whole. It is very Earth does not occupy a special place in the universe. The universe has a turn reveals how much time has elapsed since it much like when we talk about a balloon blowing uniform density (homogeneity) and occurred. If a supernova with a given redshift up: we discuss how big the entire balloon gets, looks the same in every direction looks dimmer than expected, then that superno- not how much each individual patch of the bal- (isotropy). va must be farther away than astronomers loon inflates. But we all have had experience with Though powerful, the principle thought. Its light has taken longer to reach us, those annoying party balloons that inflate un- applies only on scales much larger than a galaxy. After all, if the cosmos and hence the universe must have taken longer to evenly. One ring stretches quickly, and the end were completely uniform, it would be grow to its current size [see box on opposite takes a while to catch up. In an alternative view a thin gruel of atoms rather than a page]. Consequently, the expansion rate of the of the universe, one that jettisons the cosmologi- constellation of galaxies. Also, the universe must have been slower in the past than cal principle, space, too, expands unevenly. A principle applies in space but not in

previously expected. In fact, the distant superno- more complex picture of the cosmos emerges. ) time. We live in a special era—long enough after the big bang that vae are dim enough that the expansion of the uni- Consider the following scenario, first suggest- complex life can form but not so long verse must have accelerated to have caught up ed by George Ellis, Charles Hellaby and Nazeem Copernicus that stars have all died off. with its current expansion rate [see “Surveying Mustapha, all at the University of Cape Town in mages ( mages Copernicus is commonly associat- Spacetime with Supernovae,” by Craig J. Hogan, South Africa, and subsequently followed up by I

ed with a dethroning of humanity etty

Robert P. Kirshner and Nicholas B. Suntzeff; Sci- Marie-Noëlle Célérier of the Paris-Meudon Ob- G from any position of importance. But

entific American, January 1999]. servatory in France. Suppose that the expansion rary/ as historian Dennis Danielson of the b i University of British Columbia argues, This accelerating expansion is the big sur- rate is decelerating everywhere, as matter tugs on L although pre-Copernican Europeans prise that fired the current revolution in cosmol- spacetime and slows it down. Suppose, further, A rt placed Earth at the center of the ogy. Matter in the universe should tug at the fab- that we live in a gargantuan cosmic void—not a universe, they did not consider the ric of spacetime, slowing down the expansion, completely empty region, but one in which the center a position of importance but but the supernova data suggest otherwise. If cos- average density of matter is only a half or maybe quite the opposite—as Galileo put it, chool/Bridgeman S “the sump where the universe’s filth mologists accept the cosmological principle and a third of the density elsewhere. The emptier a

and ephemera collect.” assume that this acceleration happens every- patch of space is, the less matter it contains to Polish

34 Scientific American © 2009 SCIENTIFIC AMERICAN, INC. April 2009 don dixon Way galaxy. Over time this region gets bigger as the fabric of space stretch space of fabric the as bigger gets region this time Over galaxy. Way and a a our of Milky consider supernova region space that encompasses To means for cosmic expansion, see what than this expected. discovery are dimmer explosions have supernovae that found distant Astronomers Three [ www.SciAm.com YEARS AGO th 12 BILLION increment, the region of space increases in size by a diminishing factor. They based their expectations of of expectations their based They time each factor. In assumption. time. this over on diminishing a by down size in slowing brightness was increases supernova space expansion of cosmic region that the assumed increment, cosmologists most 1998, to Prior time to spread out, so that it appears dimmer to us. To drive this acceleration requires dark energy. dark requires more had has acceleration light this is drive it To supernova us. and than to size slower dimmer be to present used its appears to it grow that to expansion so out, longer cosmic of taken spread rate to has the time universe the observations, Consequently, supernova of now. interpretation usual the In O scenario 1: expansion is which has the same effect as cosmic acceleration but without any need for dark energy. dark for need any without but expansion rapid acceleration increasingly cosmic of as zones effect enters same it the has out, which spreads supernova a from light As is emptier than other areas, it has less matter to retard the expansion and decelerates less quickly. quickly. less decelerates and expansion the retard to matter less has it areas, other than emptier is Alternatively, perhaps expansion is decelerating but at different rates in different places. If our neighborhood scenario 2: universe is IN is universe 2: scenario Region of space LD view: expansion is D LD expansion view: YEARS AGO e basics] 12 BILLION YEARS AGO 12 BILLION

ays of region expanding Rapidly

YEARS AGO S Milky W Milky 8 BILLION BILLION 8 upernova YEARS AGO 8 BILLION BILLION 8 E ay ECE ACCEL

xpanding xpanding a H YEARS AGO 8 BILLION BILLION 8 O L

M ERA O ERA G T region expanding S ENEOUS

spreads out and eventually reaches us on the outskirts of Way.the us Milky on reaches out and the spreads eventually outskirts the from explosion Light or accelerating). is the decelerating expansion on whether depending times size half at its current (which occurs different is the when about off es universe goes like The supernova a sheet. rubber —

YEARS AGO 4 BILLION BILLION 4

S CIENTIFIC AMERIC today today today A N

35 [the big picture] A Special Place for Us In his Hitchhiker’s Guide to the Galaxy series of novels, Douglas Adams unscathed when it turns out that the universe does, in fact, revolve around imagines a torture device that drives people insane by showing them the utter him. In a case of life imitating art, many cosmologists are investigating wheth- insignificance of their place in the universe. One would-be victim emerges er our planet indeed has a special place within the grand scheme of things.

Void

vable uni er ve s rs b e O You are here

HOMOGENEOUS universe: our location is typical INHOMOGENEOUS universe: our location is special In the standard view, galaxies are lined up in a spidery pattern, but overall Alternatively, the density of matter could vary on large scales, and Earth space looks much the same everywhere, and Earth’s position is nothing special. may lie at or near the center of a relatively less dense region, or void.

slow down the expansion of space; accordingly, to travel a greater distance than it would in a the local expansion rate is faster within the void uniformly expanding universe, in which case the than it is elsewhere. The expansion rate is fastest supernova has to be farther away and therefore at the very center of the void and diminishes to- appear dimmer. ward the edge, where the higher-density exterior Another way to put it is that a variation of ex- begins to make itself felt. At any given time dif- pansion rate with position mimics a variation in ferent parts of space will expand at different time. In this way, cosmologists can explain the rates, like the unevenly inflated party balloon. unexpected supernova observations without in- Now imagine supernovae exploding in differ- voking dark energy. For such an alternative ex- ent parts of this inhomogeneous universe, some planation to work, we would have to live in a close to the center of the void, others nearer the void of truly cosmic proportions. The supernova edge and some outside the void. If we are near observations extend out to billions of light-years, the center of the void and a supernova is farther a significant fraction of the entire observable out, space expands faster in our vicinity than it universe. A void would have to be of similar size. does at the location of the supernova. As light Enormous by (almost) anyone’s standards. from the supernova travels toward us, it passes through regions that are expanding at ever fast- A Far-fetched Possibility er rates. Each region stretches the light by a cer- So how outlandish is this cosmic void? At first tain amount as it passes though, and the cumu- glance, very. It would seem to fly in the face of lative effect produces the redshift we observe. the cosmic microwave background, which is Light traveling a given distance is redshifted by uniform to one part in 100,000, not to mention less than it would be if the whole universe ex- the apparently uniform distribution of galaxies panded at our local rate. Conversely, to achieve [see “Reading the Blueprints of Creation,” by

a certain redshift in such a universe, the light has Michael A. Strauss; Scientific American, Feb dixon don

36 Scientific American © 2009 SCIENTIFIC AMERICAN, INC. April 2009 ruary 2004]. On closer inspection, however, this our observable universe would seem to be tiny. evidence may not be so conclusive. Still, there is a possible loophole. In the early The uniformity of the relic radiation merely 1990s one of the authors of what is now the stan- requires the universe to look nearly the same in dard model of the early universe, Andrei Linde, every direction. If a void is roughly spherical and and his collaborators at Stanford University if we lie reasonably close to its center, these ob- showed that although giant voids are rare, they servations do not necessarily preclude it. In ad- expand faster early on and come to dominate the dition, the cosmic microwave background has volume of the universe. The probability of ob- some anomalous features that could potentially servers finding themselves in such a structure be explained by large-scale inhomogeneity [see may not be so tiny after all. This result shows that box on next page]. the cosmological principle (that we do not live in As for the galaxy distribution, existing sur- a special place) is not always the same thing as the veys do not extend far enough to rule out a void principle of mediocrity (that we are typical ob- no a-voiding it of the size that would mimic dark energy. They servers). One can, it seems, be both typical and identify smaller voids, filaments of matter and live in a special place. Although a cosmic void mimics other structures hundreds of millions of light- dark energy, the match is not exact. Upcoming observations will years in size, but the putative void is an order of Testing the Void look for telltale differences. magnitude larger. A lively debate is now under What observations could tell whether the expan- way in astronomy as to whether galaxy surveys sion of the universe is driven by dark energy or ■■ Additional supernova observations corroborate the cosmological principle. A recent whether we are living in a special place, such as will pin down the expansion rate analysis by David Hogg of New York University at the center of a giant void? To test for the pres- and check whether it varies with and his collaborators indicates that the largest ence of a void, cosmologists need a working position, as a void model predicts. structures in the universe are about 200 million model of how space, time and matter should ■■ Galaxy clusters reflect light and, in light-years in size; on larger scales, matter ap- behave in its vicinity. Just such a model was for- effect, let us view our cosmic neigh- pears smoothly distributed, in accordance with mulated in 1933 by Abbé Georges Lemaître, borhood in the mirror. If we live in the principle. But Francesco Sylos Labini of the independently rediscovered a year later by Rich- a void, we should be able to see it. Enrico Fermi Center in Rome and his colleagues ard Tolman and further developed after World argue that the largest structures discovered so far War II by Hermann Bondi. The universe they ■■ Galaxies and galaxy clusters evolve are limited only by the size of the galaxy surveys envisaged had expansion rates that depended at a pace that depends on the expansion rate at their location and that found them. Still larger structures might not only on time but also on distance from a spe- therefore on the presence of a void. stretch beyond the scope of the surveys. cific point, just as we now hypothesize. By analogy, suppose you had a map showing With the Lemaître-Tolman-Bondi model in ■■ Neutrinos left over from the primor- a region 10 miles wide, on which a road stretched hand, cosmologists can make predictions for a dial universe could reveal a void. from one side to the other. It would be a mistake to conclude that the longest possible road is 10 Supernova 1994D (arrow) and similar explosions miles long. To determine the length of the longest are used as tracers of cosmic expansion. road, you would need a map that clearly showed the end points of all roads, so that you would know their full extent. Similarly, astronomers need a galaxy survey that is larger than the big-

eam gest structures in the universe if they are to prove the cosmological principle. Whether surveys are earch T big enough yet is the subject of the debate. For theorists, too, a colossal void is difficult ernova S p

u to stomach. All available evidence suggests that galaxies and larger structures such as filaments igh-Z S and voids grew from microscopic quantum seeds that cosmic expansion enlarged to astronomical eam and H proportions, and cosmological theory makes firm predictions for how many structures should exist with a certain size. The larger a structure le Key Project T is, the rarer it should be. The probability of a bb u

, H void big enough to mimic dark energy is less

ESA 100 / than one part in 10 . Giant voids may well ex-

NASA ist out there, but the chance of our finding one in

www.SciAm.com © 2009 SCIENTIFIC AMERICAN, INC. SCIENTIFIC AMERICAN 37 range of observable quantities. To begin, consid- [The Authors] acceleration, but their lack of pointyness means er the supernovae that first led to the inference of that they do not reproduce exactly the same re- dark energy. The more supernovae that astrono- sults as dark energy. In particular, the apparent mers observe, the more accurately they can re- rate of acceleration varies with redshift in a tell- construct the expansion history of the universe. tale way. In a paper with Kate Land, then at the Strictly speaking, these observations cannot ever University of Oxford, we showed that several rule out the void model, because cosmologists hundred new supernovae, on top of the few hun- could re-create any set of supernova data by dred we currently have, should be enough to set- Timothy Clifton and Pedro G. choosing a suitably shaped void. Yet for a void to Ferreira are cosmologists at the tle the issue. Supernova-observing missions stand be completely indistinguishable from dark ener- University of Oxford. Both study a very good chance of achieving this goal soon. gy, it would have to have some very strange prop- the physics of the early universe Supernovae are not the only observables erties indeed. and potential modifications to available. Jeremy Goodman of Princeton Uni- The reason is that the putative accelerating ex- Einstein’s general theory of relativ- versity suggested another possible test in 1995 ity. Clifton, a keen oenophile, says pansion occurs right up to the present moment. his true interest in life is Burgundy using the microwave background radiation. At For a void to mimic it exactly, the expansion rate wine. Ferreira is the author of a the time, the best evidence for dark energy had must decrease sharply away from us and in every popular-level astronomy book, The not yet emerged, and Goodman was not seeking direction. Therefore, the density of matter and State of the Universe, runs a an explanation for any unexplained phenomena energy must increase sharply away from us in ev- program for artists in residence at but proof of the Copernican principle itself. His Oxford, and participates in various ery direction. The density profile must look like projects to support science educa- idea was to use distant clusters of galaxies as an upside-down witch’s hat, the tip of which cor- tion in Africa. mirrors to look at the universe from different po- responds to where we live. Such a profile would sitions, like a celestial dressing room. Galaxy go against all our experience of what structures clusters reflect a small fraction of the microwave in the universe look like: they are usually smooth, radiation that hits them. By carefully measuring not pointy. Even worse, Ali Vanderveld and Éan- the spectrum of this radiation, cosmologists na Flanagan, both then at Cornell University, could infer some aspects of what the universe showed that the tip of the hat, where we live, would look like if viewed from one of them. If a would have to be a singularity, like the ultradense shift of viewpoint changed how the universe region at the center of a black hole. looked, it would be powerful evidence for a void If, however, the void has a more realistic, or a similar structure. smooth density profile, then a distinct observa- Two teams of cosmologists recently put this tional signature presents itself. Smooth voids still idea to the test. Robert Caldwell of Dartmouth produce observations that could be mistaken for

Surrender to the Void Most suggestions that we live in a cosmic void place us at its center, but what if we lived away from the middle? The universe would then look slightly lopsided. Håvard Alnes and Morad Amarzguioui, both at the University of Oslo, have shown that the cosmic microwave background radiation would look slightly hotter in one direction than in the other. Alignment Such an asymmetry, called a dipole, has indeed been observed in of features the microwave background. It is usually attributed to our solar system’s motion through space but could also be a sign of a lumpy universe. Furthermore, small fluctuations in the microwave background appear to align in a axis of evil, an alignment of specific direction—dubbed the “axis of evil” by João Magueijo and Kate Land, both then at Imperial College features in the cosmic micro- London [see “Is the Universe Out of Tune?” by Glenn D. Starkman and Dominik J. Schwarz; Scientific Am e r i c a n , wave background radiation,

August 2005]. This alignment picks out a preferred direction in the sky, which, though hard to imagine in a );

could be a sign that we live in ); Copernican universe, might be explained in terms of our displacement from the center of a void. A preferred an inhomogeneous universe. Ferreira ) direction would also have other effects, such as large-scale coherent motions of galaxies and galaxy clusters. Clifton map

Several researchers have claimed to have detected such a “dark flow,” but it remains controversial. alnys ( lifton ( eam ( eam zk Although it is tempting to attribute these anomalies to a giant void, this explanation does not really hold T

together. For a start, these effects each pick out different directions. Furthermore, the strength of the cosmic isa Wes imothy C cience cience dipole would suggest that we are only about 50 million light-years from the center, which is only a very small S P MA P

fraction of the total size of the putative void. —T.C. and P.G.F. /W ourtesy of T ourtesy of G NASA C C

38 Scientific American © 2009 SCIENTIFIC AMERICAN, INC. April 2009 College and Albert Stebbins of the Fermi Nation- reaching us, and the variations in the expansion al Accelerator Laboratory in Batavia, Ill., studied rate tweak their brightness and redshift. So far, precise measurements of distortions in the micro- however, the idea does not look very promising. wave background, and Juan García-Bellido of One of us (Clifton), together with Joseph Zuntz the University of Madrid and Troels Haugbølle of Oxford, recently showed that reproducing the of the University of Aarhus in Denmark looked effects of dark energy would take lots of voids of at individual clusters directly. Neither group de- very low density, distributed in a special way. tected a void; the best the researchers could do Another possibility is that dark energy is an was to narrow down the properties that such a artifact of the mathematical approximations void could have. The Planck Surveyor satellite, walking that cosmologists routinely use. To calculate the scheduled for launch this month, should be able the planck cosmic expansion rate, we typically count up to place stronger limits on the void properties how much matter a region of space contains, di- The latest spacecraft to measure and maybe rule out a void altogether. vide by the volume of the region and arrive at the the cosmic microwave background A third approach, advocated by Bruce Bassett, radiation, the European Space Agen- average energy density. We then insert this aver- Chris Clarkson and Teresa Lu, all at the Univer- cy’s Planck Surveyor, is scheduled to age density into Einstein’s equations for gravity sity of Cape Town, is to make independent mea- launch this month. and determine the averaged expansion rate of surements of the expansion rate at different loca- Planck should provide a complete the universe. Although the density varies from inventory of fluctuations in the tions. Astronomers usually measure expansion place to place, we treat this scatter as small fluc- temperature of the microwave rates in terms of redshift, which is the cumulative background, thereby completing an tuations about the overall average. effect of the expansion of all regions of space be- observational effort that began in the The problem is that solving Einstein’s equa- tween a celestial body and us. By lumping all 1960s. These fluctuations reveal tions for an averaged matter distribution is not these regions together, redshift cannot distin- what the universe looked like at the the same as solving for the real matter distribu- tender age of 400,000 years and how guish a variation of expansion rate in space from tion and then averaging the resulting geometry. it has grown since then. It could tell a variation in time. It would be better to measure us whether we live in a giant void. In other words, we average and then solve, when the expansion rate at specific spatial locations, Planck will also measure fluctua- really we should solve and then average. separating out the effects of expansion at other tions in the polarization (or direction- Solving the full set of equations for anything locations. That is a difficult proposition, though, ality) of the radiation, which could even vaguely approximating the real universe is reveal whether gravitational waves and has yet to be done. One possibility is to ob- unthinkably difficult, and so most of us resort to coursed through the ancient universe serve how structures form at different places. as a result of high-energy processes a the simpler route. Thomas Buchert of the Uni- The formation and evolution of galaxies and gal- fraction of a second after the big versity of Lyon in France has taken up the task axy clusters depend, in large part, on the local bang—or even before it. of determining how good an approximation it rate of expansion. By studying these objects at really is. He has introduced an extra set of terms different locations and accounting for other ef- into the cosmological equations to account for fects that play a role in their evolution, astrono- the error introduced by averaging before solving. mers may be able to map out subtle differences in If these terms prove to be small, then the approx- expansion rate. ➥ More To imation is good; if they are large, it is not. The Explore results so far are inconclusive. Some researchers A Not So Special Place Geocentrism Reexamined. Jeremy have suggested that the extra terms may be The possibility that we live in the middle of a Goodman in Physical Review D, enough to account for dark energy entirely, giant cosmic void is an extreme rejection of the Vol. 52, No. 4, pages 1821–1827; whereas others claim they are negligible. cosmological principle, but there are gentler pos- March 15, 1995. http://arxiv.org/ Observational tests to distinguish between sibilities. The universe could obey the cosmologi- abs/astro-ph/9506068 dark energy and the void models are set to be car- cal principle on large scales, but the smaller voids The State of the Universe: A Prim- ried out in the very near future. The Supernova and filaments that galaxy surveys have discover in Modern Cosmology. Pedro G. Legacy Survey, led by Pierre Astier of the Univer- ered might collectively mimic the effects of dark Ferreira. Phoenix, 2007. sity of Paris, and the Joint Dark Energy Mission, energy. Tirthabir Biswas and Alessio Notari, currently under development, should pin down both at McGill University, as well as Valerio Cosmology: Patchy Solutions. the expansion history of the universe. The Planck G.F.R. Ellis in Nature, Vol. 452, pages Marra and his collaborators, then at the Univer- 158–161; March 12, 2008. Surveyor satellite and a variety of ground-based sity of Padua in Italy and the University of Chi- and balloon-borne instruments will map out the cago, have studied this idea. In their models, the Living in a Void: Testing the Co- microwave background in ever greater detail. universe looks like Swiss cheese—uniform on the pernican Principle with Distant The Square Kilometer Array, a gigantic radio b whole but riddled with holes. Consequently, the Supernovae. Timothy Clifton, Pedro telescope planned for 2020, will supply us with G. Ferreira and Kate Land in Physical ediala

M expansion rate varies slightly from place to place. a survey of all the galaxies within our observable Review Letters, Vol. 101, Paper No. Rays of light emitted by distant supernovae trav- horizon. This revolution in cosmology began a AOES

/ 131302; September 26, 2008. http://

ESA el through a multitude of these small voids before arxiv.org/abs/0807.1443 decade ago, and it is far from over. ■

Analyses of primate visual pigments show that our color vision evolved in an unusual way and that the brain is more adaptable than generally thought By Gerald H. Jacobs and Jeremy Nathans

o our eyes, the world is arrayed in a Pigments and Their Past seemingly infinite splendor of hues, The spectral sensitivities of the three visual pig- Tfrom the sunny orange of a marigold ments responsible for human color vision were flower to the gunmetal gray of an automobile first measured more than 50 years ago and are chassis, from the buoyant blue of a midwinter now known with great precision. Each absorbs sky to the sparkling green of an emerald. It is re- light from a particular region of the spectrum markable, then, that for most human beings any and is characterized by the wavelength it absorbs KEY CONCEPTS color can be reproduced by mixing together just most efficiently. The short-wavelength (S) pig- three fixed wavelengths of light at certain inten- ment absorbs light maximally at wavelengths of ■ ■ The color vision of sities. This property of human vision, called about 430 nanometers (a nanometer is one bil- humans and some other primates differs from that trichromacy, arises because the retina —the layer lionth of a meter), the medium-wavelength (M) of nerve cells in the eye that captures light and pigment maximally absorbs light at approxi-

of nonprimate mammals. ) transmits visual information to the brain—uses mately 530 nanometers, and the long-wavelength ■ ■ It is called trichromacy, Key Concepts only three types of light-absorbing pigments for (L) pigment absorbs light maximally at 560 because it depends on color vision. One consequence of trichromacy is nanometers. (For context, wavelengths of 470, ■ ■ Loiametumthree types ofdolore light- ting photoillustration Lumsandioactivated pigments cor ad Bor in in that computer and television displays can mix 520 and 580 nanometers correspond to hues that red, green and blue pixels to generate what we the typical human perceives as blue, green and kkanda ( utatumthe retina vulput of the wisi eye. eum I - eu feum quam. perceive as a full spectrum of color. yellow, respectively.) g ■ ■ Analyses of the genes Although trichromacy is common among pri- These pigments, each consisting of a protein eadin

■ ■ Equatfor those acipit, pigments vullaoreet give y R c

mates, it is not universal in the animal kingdom. complexed with a light-absorbing compound u iritclues lorpercin to how trichromacyhenisismodit ); L ulputemevolved from ipit nonsequthe color isis - Almost all nonprimate mammals are dichro- derived from vitamin A, sit in the membranes chimps civision eriliquat. of nonprimate mam- mats, with color vision based on just two kinds of cone cells: photoreceptive nerve cells in the ( of visual pigments. A few nocturnal mammals retina named for their tapering shape. When a mals, which have only two Corbis ■ ■ Um zzriurem vulputatet kinds of photopigments. have only one pigment. Some birds, fish and rep- pigment absorbs light, it triggers a cascade of

praesse magna consequis lsdale tiles have four visual pigments and can detect molecular events that leads to the excitation of E ■ ■ nitThe diatiscidui authors created eum eu b

quam,trichromatic quipis mice nosto by odiinsert- - ultraviolet light invisible to humans. It seems, the cone cell. This excitation, in turn, activates Bo ); ametuming a human dolore pigment ting eum gene- then, that primate trichromacy is unusual. How other retinal neurons that ultimately convey painting sandiointo the cor mouse ad dolore genome. del did it evolve? Building on decades of study, re- (

cent investigations into the genetics, molecular Corbis ullutatThe experiment dolortio revealedeuis ac-  CHIMPANZEES, like humans, can distinguish cumsandit,unexpected conseplasticity feu in fac - biology and neurophysiology of primate color among colors that other mammals cannot see. cummythe mammalian nia. brain. vision have yielded some unexpected answers as What observers see in a Kandinsky reflects the —The Editors well as surprising findings about the flexibility properties of the paints, the nature of the illumi-

of the primate brain. nation, and the color vision system of the viewers. GeoffreyClements

40 Scientific American © 2009 SCIENTIFIC AMERICAN, INC. April 2009 © 2009 SCIENTIFIC AMERICAN, INC. www.SciAm.com © 2009 SCIENTIFIC AMERICAN, INC. SCIENTIFIC AMERICAN 41 a signal along the optic nerve to the brain. Although the absorption spectra of the cone Optic nerve Retina to brain pigments have long been known, it was not until the 1980s that one of us (Nathans) identified the genes for the human pigments and, from the DNA sequences of those genes, determined the sequence of amino acids that constitutes each pigment protein. The gene sequences revealed that the M and L pigments are almost identical. Subsequent experiments showed that the difference in spectral sensitivity between them derives from substitutions in just three of the 364 amino Light Cone acids from which each is built.

Experiments also showed that the M- and L- Rod pigment genes sit next to each other on the X chromosome, one of the two sex chromosomes. (Men have one X and one Y, whereas women Retina have two Xs.) This location came as no surprise, because a common anomaly in human color per-  RETINA, a layer of nerve cells at the back of the eye, transmits visual information to ception, red-green color blindness, had long been the brain via the optic nerve. Color vision depends on cones: tapered sensory cells that known to occur more often in men than in wom- contain light-activated pigments. Other light-sensitive cells called rods function in dim en and to be inherited in a pattern indicating that light and do not usually participate in color vision. The rods and cones, known collec- the responsible genes reside on the X chromo- tively as photoreceptors, sit behind other cell types that support vision. some. The S-pigment gene, in contrast, is located on chromosome 7, and its sequence shows that A known mechanism for gene duplications of the encoded S pigment is related only distantly this type occurs during the formation of eggs to the M and L pigments. and sperm. As cells that give rise to eggs and By the mid-1990s comparisons of these three sperm divide, pairs of chromosomes often swap pigment genes with those of other animals had parts in a process called recombination, and oc- provided substantial information about their [The Authors] casionally an unequal exchange of genetic mate- history. Almost all vertebrates have genes with Gerald H. Jacobs is research rial leads to the production of a chromosome ) sequences that are very similar to that of the hu- professor in the department of that possesses extra copies of one or more genes. psychology and the Neuroscience Nathans man S pigment, implying that some version of a Useful mutations subsequently introduced in Research Institute at the University shorter-wavelength pigment is an ancient ele- of California, Santa Barbara. The those duplicate genes can then be maintained by niversity ( ment of color vision. Relatives of the two longer- author of more than 200 articles natural selection. That is, by aiding survival, wavelength pigments (M and L) are also wide- and book chapters on the visual helpful mutations get passed down to future gen- system, he deciphered the genetic spread among vertebrates and likely to be quite erations and spread within the population. ns Hopkins U mechanism that gives rise to h ancient. But among mammals, the presence of In the case of primate color vision, trichroma- trichromatic color vision in New both M- and L-like pigments has been seen only World primates. Jeremy Nathans, cy based on the “new” M and L pigments (along in a subset of primate species—a sign that this who worked out the genetic with the S pigment) presumably conferred a se- feature probably evolved more recently. sequences of the human visual lective advantage over dichromats in some envi- ); Courtesy of Jo pigment genes and the structure Most nonprimate mammals have only one ronments. The colors of ripe fruit, for example, Jacobs s (

of the corresponding proteins, is b longer-wavelength pigment, which is similar frequently contrast with the surrounding foli- o professor in the departments of c to the longer-wavelength primate pigments. The molecular biology and genetics, age, but dichromats are less able to see such con- gene for the longer-wavelength mammalian neuroscience and ophthalmology trast because they have low sensitivity to color pigment is also located on the X chromosome. at the Johns Hopkins University differences in the red, yellow and green regions Those features raised the possibility, then, that School of Medicine and an investi- of the visual spectrum. An improved ability to gator at the Howard Hughes the two longer-wavelength primate pigment identify edible fruit would likely aid the survival Medical Institute. genes first arose in the early primate lineage in of individuals harboring the mutations that con- ); Courtesy of Gerald H. Ja this way: a longer-wavelength mammalian pig- fer trichromacy and lead to the spread of those ment gene was duplicated on a single X chromo- mutant genes in the population. some, after which mutations in either or both The mechanisms outlined earlier—gene du- illustrations retina copies of the X-linked ancestral gene produced plication followed by mutation leading to DNA two quite similar pigments with different ranges sequence divergence—would seem to be a rea-

of spectral sensitivity—the M and L pigments. sonable explanation for the evolution of the pri- andrew swift (

mate M- and L-pigment genes because that se- Two Kinds of Mammalian1 Color Vision ries of events is known to have occurred in other Most mammals are dichromats; their color vision comes from just two kinds of visual gene families. Consider, for example, the genes pigments (top panel): one that absorbs short-wavelength light maximally (blueFraction curve) and encoding the hemoglobins, proteins that carry of light one that is more sensitive to longer wavelengths (green curve). But humans andabsorbed some oxygen in the blood. The genes for fetal hemo- other primates have trichromatic color vision (lower panel). They see more colorsby pigment because globin, which is produced beginning in the sec- they use three pigment types: a short-wavelength pigment (blue curve) and two kinds of ond month in utero, and the genes for adult he- longer-wavelength pigments (green and red curves). moglobin seem to have originated as duplicates of a single ancestral gene that then mutated into Dichromatic variants with differing affinities for oxygen. 1 400 600 0 Likewise, immunoglobulins, the proteins that Nanometers Fraction mediate the antibody response of the immune of light system, come in a great variety and arose from absorbed by pigment duplication of a single, ancestral gene.

Two Roads to Trichromacy The real story of the evolution of primate trichromacy, however, turns out to be both more com- 400 600 plicated and more interesting. A critical clue 0 Nanometers came from the discovery that two different genetic mechanisms for trichromatic vision seem to operate in primates: one in the Old World primates (the group that evolved in sub-Saharan Trichromatic Africa and Asia and that includes gibbons, chim- 1 panzees, gorillas and humans) and another in the New World primates (species from Central and South America such as marmosets, tamarins and squirrel monkeys). Humans and other Old World primates carry both M- and L-pigment genes on each of their X chromosomes and have trichromatic vision.

But in testing the color vision of New World pri- 1 400 600 ) 0 mates over the past several decades, one of us Nanometers (Jacobs) discovered that trichromacy occurs

color spectrums color only in a subset of females. All of the New World males and roughly a third of the New World fe- kkanda (

I males examined showed the lack of sensitivity DNA. Allelic variation occurs in many genes, but - g Evolutionary to color differences in the middle-to-long wave- the small differences in DNA sequence between

eadin ADVANTAGE? lengths that is typical of dichromats. Trichroma- alleles hardly ever translate to functional differ- y R c u cy was not universal among primates after all. ences. In New World primates, however, the var- The colors of ripe fruit frequently ); L 400contrast with surrounding600 foliage, To explain this curious pattern, several inves- ious X-linked pigment alleles give rise to 0pig- and trichromatsNanometers can discern such tigators studied the number and arrangement of ments having different spectral sensitivities. Typ- raspberries contrasts better than dichromats ( cone pigment genes in these New World mon- ical New World primate species such as squirrel do. The improved ability to ident keys. Most species turned out to have one short- monkeys, for example, have three alleles of the ify ripe fruit is one way trichro-

Getty Images wavelength pigment gene (presumably located X-linked cone pigment gene in their gene pool: matic vision could have aided on a nonsex chromosome) and only one longer- one coding for a protein similar to the human M survival, leading to the spread tley tley gh of the genes for trichromacy in L i wavelength gene, located on the X chromosome. pigment, a second coding for a protein similar to primate populations. In other words, their genetic endowment of vi- the human L pigment, and a third coding for a ); Justin Justin ); sual pigments was comparable to that of the di- pigment with light-absorption properties rough- frogs ( chromatic mammals. How, then, could any of ly midway between the first two. them be trichromats? Having two X chromosomes, a female squir-

Getty Images The answer is that the gene pool of New rel monkey—and only a female—might inherit World primates includes several variants, or al- two different longer-wavelength alleles (one on

umway umway Sh leles, of the X-linked pigment gene—different each X chromosome), thereby acquiring trichro-

Gail Gail versions with slightly modified sequences of macy. About a third of all females, however, will

Two Designs for 2 pigment genes per X X TES Primate Vision Male chromosome Trichromatic Y No pigment The genetic basis of trichromacy in Old World and gene on Y chromosome New World primates differs. In both, a gene encoding a short-wavelength pigment (blue) sits on a XX nonsex chromosome. The Old World primates also

RLD PRIMA WO Female Trichromatic have two longer-wavelength pigment genes (red

and green) on each X chromosome. Hence, males OLD (with one X) as well as females (with two Xs) have three pigment genes and are trichromats. 1 pigment allele per X X New World primates have three variants TES chromosome (“alleles”) of a longer-wavelength X-linked pigment Male Y Dichromatic gene in their gene pool (red, yellow and green), ? but any given X carries just one of these alleles. Consequently, only females having dissimilar If both X chromosomes XX have same pigment allele: pigment alleles on their two Xs are trichromats. Dichromatic RLD PRIMA WO Female If X chromosomes have ? ? different pigment alleles:

NEW Trichromatic

inherit the same pigment allele on both their no acids that confer a maximum spectral sensi- X chromosomes and end up as dichromats, like tivity at 530 nanometers, and all L pigments the unlucky males. One can think of New World share a second set of three amino acids that con- primate trichromacy as the poor man’s—or, fers a maximum spectral sensitivity at 560 nano- more accurately, the poor woman’s—version of meters. From studies of the absorption spectra the ubiquitous trichromacy that Old World pri- of other longer-wavelength pigments, we know mates enjoy [see box above]. that sequence changes in a variety of other ami- The disparity in color vision between the New no acids can shift the maximal sensitivity of this OLD and Old World primates provides a window onto family of pigments to longer or shorter wave- WORLD the evolution of color vision in both groups. The lengths. It seems unlikely, then, that New and two primate lineages began to diverge about 150 Old World primates converged independently on PRIMATES evolved in Africa and Asia over millions of million years ago, with the progressive separa- identical sets of amino acids to shift the sensitiv- years and today include great apes tion of the African and South American conti- ities of their longer-wavelength pigments. (humans, orangutans, gorillas, nents; their genetic isolation appears to have been Instead it makes more sense to think that al- bonobos and chimpanzees), complete by about 40 million years ago. One lelic variation like that in today’s New World ) as well as gibbons, langurs, might suspect that the two mechanisms of primates was the primitive condition, present in mandrill

macaques and mandrills. The Old ( World primate lineage became trichromacy evolved independently, after the the common ancestor of both groups, and that isolated from that of the New New and Old World primate lineages separated. its appearance was the first step in the path to World—Central and South Both groups could have started out as dichro- trichromacy for both [see box on opposite page]. Minden Pictures Minden America—when the African and mats, with the standard mammalian comple- The various pigment alleles probably arose by

South American continents uoso ment of one shorter-wavelength pigment and one successive rounds of mutation in the mammali- R became fully separated about longer-wavelength pigment. The longer-wave- an longer-wavelength pigment gene some time

40 million years ago. Cyril); length pigment gene in the Old World primates before the Old and New World primate lineages globe could have undergone the gene duplication fol- became isolated. (We suppose that the interme- ialists ( ialists

lowed by sequence divergence that we discussed diate-wavelength pigment was part of this prim- c

earlier. In New World primates the longer-wave- itive complement because its amino acid se- spe length pigment gene could have simply under- quence contains a subset of the three sequence

gone sequence divergence, with successive muta- changes that distinguish L from M pigments and mappin g );

tions creating various longer-wavelength pig- because its absorption spectrum is partway be- genes ment alleles that persisted in the population. tween the two.) Then, after the two primate kkanda (

Yet comparison of the amino acid sequences groups became separated, a rare error in recom- I - of the X-linked visual pigments suggests another bination occurred in a female of the Old World g

scenario. Across both Old and New World pri- lineage that happened to be carrying two differ- eadin y R c u

 Mandrill mates, all M pigments share one set of three ami- ent alleles of the longer-wavelength pigment L

44 Scientific American © 2009 SCIENTIFIC AMERICAN, INC. April 2009 gene. This rare event placed an M allele along- different cone types are arranged in the requisite side an L allele on a single X chromosome, there- mosaic. Yet every cone cell in a trichromat har- by allowing trichromacy to extend to males as bors genes for all three pigments. Exactly how a well as all females. cone cell “decides” to express just one pigment That genetic innovation granted such a gene is not entirely clear. strong selective advantage to its carriers that Cells switch on, or express, their genes by X chromosomes having only one longer-wave- way of transcription factors: dedicated DNA length pigment gene were ultimately lost from binding proteins that attach near a regulatory the gene pool of Old World primates. Among region called a promoter, thereby triggering a se- the geographically and genetically separate ries of events leading to synthesis of the protein New World primates, the primitive system of encoded by the gene. For the short-wavelength three longer-wavelength alleles persisted. photoreceptors, it appears that during fetal de- White-bellied spider monkey  velopment transcription factors activate the gene The Role of Randomness for the S pigment. Some unknown process also NEW WORLD Another surprising implication of our findings inhibits expression of the genes for the longer- MONKEYS occupy in New and Old World primates concerns the wavelength pigments in these cells. Central and South America and role of randomness in trichromacy. We are not But an additional mechanism governs pig- tend to be smaller than their Old referring here to the random genetic mutations ment gene expression in the longer-wavelength World cousins. They include such that at the outset gave rise to the complement of cones in New World primates, and this mecha- species as marmosets, pigment genes that confer trichromacy. Biolo- nism involves an inherently random process. In tamarins, squirrel monkeys, spider gists have generally found that once a beneficial female New World primates that have different monkeys, howler trait has evolved by this chance mechanism, it pigment alleles on their two X chromosomes, monkeys and typically becomes “hardwired”: that is, cellular which allele any given cone cell expresses de- capuchins. processes that do not stray from a predetermined pends on a molecular coin toss known as blueprint meticulously orchestrate the develop- X-inactivation. In this process, each female cell ment of the trait in each individual. Yet it seems randomly disables one of its two X chromo- that for primate color vision, random events in each organism and even in each developing cone cell play a large—indeed, an essential—role. [FINDINGS] To explain how randomness helps to produce trichromacy, we must first review how cone cells How Primate Trichromacy Evolved

) transmit information about color to the brain. It Comparison of the genetic basis of color vision in New World and Old World primates turns out that having three pigment types, while indicates the key evolutionary steps that led to trichromatic color vision in some female necessary for trichromatic vision, is just an ini- New World monkeys and in both genders of Old World primates. tial condition. Neural processing of the signals generated by the various photoreceptors is the X next step. This step is critical because individual white-bellied spider monkey spider white-bellied ( cone cells cannot convey specific information XX X about wavelength. Excitation of each photore- = ceptor can be triggered by a range of different Minden Pictures Minden X X X X X wavelengths, but the cone cannot signal what xford

O particular wavelengths within that band it has Recombination Old World error vision ete P absorbed. For example, it could produce the ); same size signal whether it is hit by 100 photons Original Mutation Mutation globe condition X of a wavelength it absorbs well or by 1,000 pho- ialists ( ialists

c tons of a wavelength it absorbs poorly. To distin-

spe guish among colors, the visual system must compare the responses of neighboring cones having New World vision (3 X-linked alleles in gene pool)

); mappin g ); different pigment types.

genes For such comparisons to work optimally, In a common ancestor of both Old and New World from each other, an error in recombination—the each cone cell must contain just one type of pig- primates, an ancestral X-linked longer-wave- process in which chromosomes swap parts during length pigment gene (green at far left) underwent formation of eggs and sperm—in an Old World kkanda (

I ment, and cones making different pigments must - successive mutations, yielding three longer-wave- primate female placed two different alleles g lie close to one another in a kind of mosaic. In length pigment alleles in the gene pool (green, together on the same X chromosome (far right).

eadin fact, in the primate retina each cone cell does yellow and red); these changes persist in modern Because this condition gave a selective advan- y R New World primates. After the Old World and tage to males as well as all females, it became the c u

L contain only a single type of visual pigment, and New World primate lineages became isolated norm in present-day Old World primates.

© 2009 SCIENTIFIC AMERICAN, INC. www.SciAm.com © 2009 SCIENTIFIC AMERICAN, INC. SCIENTIFIC AMERICAN 45 [SURPRISING DISCOVERIES] somes early in development. X-inactiva- Randomness in the Retina tion ensures that just one pigment allele will be expressed (that is, one type of Each individual cone cell contains genes for all three color pig- pigment will be made) in any longer- ments but selects only one of the three to activate and shuts down the other two. The process that controls selection of the wavelength cone cell. Because the pro- short-wavelength pigment gene is not known in detail. But the cess is random—half of all cells ex- mechanisms that determine selection of one of the two longer- press genes encoded by one X chromo- wavelength pigment genes appear to be random, and the local some, and the other half express genes distribution of longer-wavelength cone types in the retina appears to encoded by the second X chromosome— be random as well (computer rendition at upper right). it also ensures that the longer-wavelength cones in New World primate females will be in- New World Coin Toss termingled across the surface of the retina in a mosaic that permits trichromacy. X X X-inactivation occurs in all mammals and is Cell with two essential for species survival. Without it, female X chromosomes cells would use both X chromosomes to produce proteins, causing the sexes to differ in the amounts of proteins made and thus impairing Cell division development in one or both of the genders. But  In New World primates the selection of a longer-wave- because Old World primates have both M- and length pigment gene is L-pigment genes on each X chromosome, X X X X accomplished by X-inactivation, a process in which a X-inactivation alone does not narrow expres- X-inactivation female cell randomly disables sion to just one pigment gene per cone cell in of one chromosome one of its two X chromosomes early in embryonic develop- those animals. Another mechanism must be op- Retinal mosaic ment. If the female has erating as well. different pigment alleles on Research by Nathans suggests that which of her X chromosomes, inactivation of one of the Xs in each the two X-linked pigment genes an Old World cell will produce a mosaic of primate cone cell expresses is determined by a longer-wavelength cone types. nearby DNA sequence known as the locus control region. The choice is probably made during development when in each cone cell the locus Old World Serendipity control region interacts with one and only one of the two adjacent pigment gene promoters— that of either the M or the L pigment, but not X X both—and switches on that gene. The particu- lars of the interaction have not yet been characterized in detail, but current evidence suggests that this choice may be random. ) retina Cell division If this pairing of the locus control region and ( a promoter is indeed determining pigment gene expression in cone cells and if it is in fact ran- X X X X dom, then the distribution of M and L cones

X-inactivation within any small region of the Old World pri- Rochester of University of one chromosome  Old World primates have two mate retina should be random as well. Studies by

kinds of longer-wavelength illiams pigment genes on a single David Williams of the University of Rochester W

X chromosome, so a second avid and his colleagues show that within the techni- D step is necessary to narrow pigment types to one per cone cal limits of current methods for mapping cone X X X X cell. X-inactivation takes one cell distribution, this prediction holds. LCR X chromosome out of play in female cells. Then, in cells of Courtesy); of LCR activation

both genders, a gene regulator The Accidental Colorist genes of just one gene called the locus control region Studies examining the underpinnings of primate (LCR) interacts at random with kkanda (

color vision also imply that certain retinal and I just one of the longer-wave- - length pigment genes, switch- brain mechanisms involved in longer-wave- g — ing only that gene on again length color vision may be highly plastic. eadin creating a random mosaic of y R c u

cone types. Although dedicated circuits exist for comparing L

46 Scientific American © 2009 SCIENTIFIC AMERICAN, INC. April 2009 visual information from the S cones with the The suggestion of neural plasticity in color vi- super combined signal from the longer-wavelength sion led us to an intriguing question. We imag- color vision? cones, the brain and retina seem to be more ine that the first step in the evolution of primate improvisational in comparing signals from M trichromacy was emergence in an early female cones with those from L cones. In particular, the ancestor to all present-day primates of a second visual system seems to learn the identity of these longer-wavelength X-linked allele. Could the an- cones by experience alone—that is, by monitor- cestral primate brain have improvised enough to ing the cones’ responses to visual stimuli. “use” the new pigment right away, without also What is more, it appears that the principal evolving new neural circuitry? Could acquiring neural pathway that conveys responses from a third type of pigment be enough in itself to add these longer-wavelength cones may not even be another dimension to color vision? Some women have four types of specifically dedicated to color vision. Rather the It occurred to us that we might test this idea visual pigments instead of three. ability to extract information about hue from if we could re-create that initial step in the evo- The fourth pigment resulted from the L and M cones may be a happy accident lution of primate trichromacy in a dichromatic a mutation in one of the longer- wavelength X-linked pigment made possible by an ancient neural apparatus for mammal such as a laboratory mouse. We began genes and is known to shift the high-resolution spatial vision, which evolved to this experiment by genetically engineering a spectral sensitivity of the retina. detect the boundaries of objects and their dis- mouse X chromosome so that it encoded a hu- Whether this shift actually creates tance from the viewer. John Mollon of the Uni- man L pigment instead of a mouse M pigment, the ability to perceive a broader versity of Cambridge points out that in primates thereby introducing allelic variation of the kind range of hues is under active

) investigation. Thus far color

eye high-resolution spatial vision is mediated by the we believe may have occurred millions of years ( vision testing has not produced longer-wavelength cones and involves the same ago in dichromatic primates. We then demon- consistent evidence for tetrachro- kind of neural processing that longer-wave- strated that the resulting line of mice expressed matic vision, and humans who Getty Images length color vision does—that is, a comparison the human gene in their cone cells and that the have this ability—if they exist— old b would not necessarily be aware of

ie of the excitation of one L or M cone with the av- human L pigment transmitted light signals with D

e their visual anomaly. g erage excitation of a large number of its L and M an efficiency comparable to that of the mouse neighbors. No separate circuitry has yet been M pigment. In addition, the mice expressing the ); Geor); found for longer-wavelength color vision, and human L pigment were, as expected, sensitive to mouse ( perhaps none is required. In this view, trichro- a broader range of wavelengths than ordinary gh ro matic color vision can be considered a hobby of mice were. ris K K the preexisting spatial vision system. But for our purposes, the key question was: ➥ More To Could female mice having two different X chro- Explore mosome pigment genes use the retinal mosaic of GENETICALLY ENGINEERED MOUSE has learned to The Evolution and Physiology approach the one panel in three that is a differ- M and L cones produced by X-inactivation not of Human Color Vision: Insights ent color from the others, revealing that it can only to sense but to make discriminations within from Molecular Genetic Studies see shades of orange that normal mice, as di- this broader range of wavelengths? The short and of Visual Pigments. J. Nathans in chromats, would not be able to distinguish from remarkable answer is that they can. Neuron, Vol. 24, No.2, pages 299–312; blue. The mouse gained this ability because it In laboratory tests, we were able to train fe- October 1999. possesses a human longer-wavelength visual males having both M and L pigments to discrim- Genetically Engineered Mice pigment gene in addition to its two native pig- inate among green, yellow, orange and red pan- with an Additional Class of Cone ment genes. The experiment demonstrates the els that, to ordinary mice, look exactly the same. Photoreceptors: Implications for remarkable plasticity of the mammalian brain, Along with the new L pigment, these mice ap- the Evolution of Color Vision. because the mouse can use its new pigment parently acquired an added dimension of senso- P. M. Smallwood et al. in Proceedings without having nerve cells specifically wired for of the National Academy of Sciences ry experience, implying that the mammalian interpreting its signals. USA, Vol. 100, No. 20, pages 11706– brain has the innate ability to extract informa- 11711; September 30, 2003. tion from novel and qualitatively different types of visual input. Emergence of Novel Color Vision This finding has implications for the evolution in Mice Engineered to Express a Human Cone Pigment. G. H. Jacobs, of sensory systems in general, because it suggests G. A. Williams, H. Cahill and that changes at the “front end” of the system—in J. Nathans in Science, Vol. 315, the genes for sensory receptors—can drive the pages 1723–1725; March 23, 2007. evolution of the entire system. With respect to primate trichromacy, the mouse experiment also Primate Color Vision: A Comparative Perspective. suggests that the very first primate with two dif- G. H. Jacobs in Visual Neuroscience, ferent longer-wavelength pigments saw a world Vol. 25, Nos. 5–6, pages 619–633; of color no primate had ever seen before. ■ September 2008.

The Post-Traumatic Stress Trap

A growing number of experts insist Stevens, now a major and still on reserve duty while he works as a physician’s assistant, is far from alone in worrying about the reach of PTSD. that the concept of post-traumatic stress Over the past five years or so, a long-simmering academic debate over PTSD’s conceptual basis disorder is itself disordered and and incidence has begun to boil over. It is now splitting the practice of trauma psychology and that soldiers are suffering as a result roiling military culture. Critiques originally raised by military historians and a few psychol- By David Dobbs ogists are now advanced by a broad array of experts—indeed, giants of psychology, psychiatry and epidemiology. They include Columbia Uni- n 2006, soon after returning from military versity’s Robert L. Spitzer and Michael B. First, service in Ramadi, Iraq, during the bloodiest who oversaw the last two editions of the Ameri- Iperiod of the war, Captain Matt Stevens of the can Psychiatric Association’s Diagnostic and Vermont National Guard began to have a prob- Statistical Manual of Mental Disorders, the lem with PTSD, or post-traumatic stress disor- DSM-III and DSM-IV; Paul McHugh, former der. Stevens’s problem was not that he had PTSD. chair of Johns Hopkins University’s psychiatry It was that he began to have doubts about PTSD: department; Michigan State University epidemi- the condition was real enough, but as a diagno- ologist Naomi Breslau; and Harvard University sis he saw it being wildly, even dangerously, psychologist Richard J. McNally, a leading au- overextended. thority in the dynamics of memory and trauma Stevens led the medics tending an armored and perhaps the most forceful of the critics. The brigade of 800 soldiers, and his team patched to- diagnostic criteria for PTSD, they assert, repre- KEY CONCEPTS gether GIs and Iraqi citizens almost every day. sent a faulty, outdated construct that has been He saw horrific things. Once home, he said he badly overstretched so that it routinely mistakes ■ ■ The syndrome of post- had his share of “nights where I’d wake up and depression, anxiety or even normal adjustment traumatic stress disorder (PTSD) is under fire be- it would be clear I wasn’t going to sleep again.” for a unique and especially stubborn ailment. cause its defining criteria He was not surprised: “I would expect people This quest to scale back the definition of are too broad, leading to to have nightmares for a while when they came PTSD and its application stands to affect the ex- rampant overdiagnosis. back.” But as he kept track of his unit in the U.S., penditure of billions of dollars, the diagnostic he saw troops greeted by both a larger culture framework of psychiatry, the effectiveness of a ■ ■ The flawed PTSD concept may mistake soldiers’ and a medical culture—especially in the Veter- huge treatment and disability infrastructure, natural process of adjust- ans Administration (VA)—that seemed reflex- and, most important, the mental health and fu- ment to civilian life for ively to view bad memories, nightmares and any ture lives of hundreds of thousands of U.S. com- dysfunction. other sign of distress as an indicator of PTSD. bat veterans and other PTSD patients. Standing “Clinicians aren’t separating the few who re- in the way of reform is conventional wisdom, ■ ■ Misdiagnosed soldiers receive the wrong treat- ally have PTSD from those who are experiencing deep cultural resistance and foundational con- ments and risk becoming things like depression or anxiety or social and re- cepts of trauma psychology. Nevertheless, it is mired in a Veterans Ad- integration problems or who are just taking some time, as Spitzer recently argued, to “save PTSD ministration system that time getting over it,” Stevens says. He worries from itself.” encourages chronic that many of these men and women are being disability. pulled into a treatment and disability regime that Casting a Wide Net —The Editors will mire them in a self-fulfilling vision of a brain The overdiagnosis of PTSD, critics say, shows rewired, a psyche permanently haunted. in the numbers, starting with the seminal study

48 Scientific American © 2009 SCIENTIFIC AMERICAN, INC. April 2009 of PTSD prevalence, the 1990 National Viet- significant impairment”—the level generally re- DISTRESS CAN BE a normal nam Veterans Readjustment Survey (NVVRS). quired for diagnosis and insurance compensa- response to pain and loss or The NVVRS covered more than 1,000 male tion in most mental illness—the rates fell yet a sign of a psychic wound that is Vietnam vets in 1988 and reported that 15.4 further, to 5.4 percent at the time of the survey failing to heal. Critics of PTSD diagnostic criteria, including percent of them had PTSD at the time and that and 11 percent lifetime. It was not one in three many soldiers, feel that return- 31 percent had suffered it at some point since veterans who eventually developed PTSD, but ing veterans’ natural process of the war. That 31 percent has been the standard one in nine—and only one in 18 had it at any adjustment is often mislabeled estimate of PTSD incidence among veterans given time. The NVVRS, in other words, ap- as a dysfunctional state. ever since. pears to have overstated PTSD rates in Vietnam In 2006, however, Columbia epidemiologist vets by almost 300 percent. Bruce P. Dohrenwend, hoping to resolve nag- “PTSD is a real thing, without a doubt,” Mc- ging questions about the study, reworked the Nally says. “But as a diagnosis, PTSD has be- numbers. When he had culled the poorly docu- come so flabby and overstretched, so much a mented diagnoses, he found that the 1988 rate part of the culture, that we are almost certainly was 9 percent and the lifetime rate 18 percent. mistaking other problems for PTSD and thus McNally shares the general admiration for mistreating them.” Dohrenwend’s careful work. Soon after it was The idea that PTSD is overdiagnosed seems published, however, McNally asserted that to contradict reports of resistance in the military Dohrenwend’s numbers were still too high be- and the VA to recognizing PTSD—denials of cause he counted as PTSD cases those veterans PTSD diagnoses and disability benefits, military

New York Times with only mild, subdiagnostic symptoms, peo- clinicians discharging soldiers instead of treat- ple rated as “generally functioning pretty well.” ing them, and a disturbing increase in suicides

TYLER HICKS If you included only those suffering “clinically among veterans of the Middle East wars. Yet the

www.SciAm.com © 2009 SCIENTIFIC AMERICAN, INC. SCIENTIFIC AMERICAN 49 The construction of this definition is suspect. PTSD: A Problem Defined To start with, the link to a traumatic event, by Its Cause which makes PTSD almost unique among complex psychiatric diagnoses in being defined by n the current American Psychiatric Association’s Diagnostic and Statistical Manual of an external cause, also makes it uniquely prob- IMental Disorders (DSM-IV), the first diagnostic criterion for post-traumatic stress disor- lematic, for the tie is really to the memory of an der (PTSD) is having experienced trauma: event. When PTSD was first added to theDSM- “The person has been exposed to a traumatic event in which both of the following have III in 1980, traumatic memories were consid- been present: (1) the person experienced, witnessed, or was confronted with an event or events that involved actual or threatened death or serious injury, or a threat to the physical ered reasonably faithful recordings of actual integrity of self or others; (2) the person’s response involved intense fear, helplessness, events. But as research since then has repeatedly or horror.” shown, memory is spectacularly unreliable and The presence of three clusters of symptoms—reexperiencing the event, for example, via malleable. We routinely add or subtract people, nightmares or flashbacks; numbing or withdrawal; and hyperarousal, evident in irritability, details, settings and actions to and from our insomnia, aggression or poor concentration—for more than a month and to the extent that memories. We conflate, invent and edit. they cause “clinically significant distress or impairment in social, occupational or other In one study by Washington University mem- important areas of functioning” completes the syndrome’s definition. ory researcher Elizabeth F. Loftus, one out of Critics of this diagnostic construct argue that the symptoms themselves can be charac- four adults who were told they were lost in a teristic of a wide array of other disorders and may appear together in people who have not shopping mall as children came to believe it. experienced trauma. Some insisted the event happened even after the PTSD was first defined in theDSM-III, published in 1980, in response to anti–Vietnam War psychiatrists and veterans who sought a diagnosis to recognize what they saw as the ruse was exposed. Subsequently, bounteous re- unique suffering of Vietnam vets. —D.D. search has confirmed that such false memories are common [see “Creating False Memories,” by Elizabeth F. Loftus; Scientific American, September 1997]. two trends are consistent. The VA’s PTSD case- Soldiers enjoy no immunity from this tenden- load has more than doubled since 2000, mostly cy. A 1990s study at the New Haven, Conn., VA because of newly diagnosed Vietnam veterans. hospital asked 59 Gulf War veterans about their The poor and erratic response to current soldiers experiences a month after their return and again and recent vets, with some being pulled quickly two years later. The researchers asked about 19 [The Author] into PTSD treatments and others discouraged or specific types of potentially traumatic events, denied, may be the panicked stumbling of an such as witnessing deaths, losing friends and see- overloaded system. ing people disfigured. Two years out, 70 percent Overhauling both the diagnosis and the VA’s of the veterans reported at least one traumatic care system, critics say, will ensure better care event they had not mentioned a month after re- for genuine PTSD patients as well as those being turning, and 24 percent reported at least three misdiagnosed. But the would-be reformers face such events for the first time. And the veterans fierce opposition. “This argument,” McNally recounting the most “new memories” also re- notes, “tends to really piss some people off.” Vet- ported the most PTSD symptoms. David Dobbs is a contributing erans send him threatening e-mails. Colleagues To McNally, such results suggest that some editor of Scientific American Mind accuse him of dishonoring veterans, dismissing veterans experiencing “late-onset” PTSD may and was the founding editor of the suffering, discounting the costs of war. Dean G. be attributing symptoms of depression, anxiety Mind Matters blog on www. Kilpatrick, a University of South Carolina trau- or other subtle disorders to a memory that has SciAmMind.com. He also regularly matologist and former president of the Inter been elaborated and given new significance—or writes on medicine, nature, educa- tion and culture for the New York national Society for Traumatic Stress Studies even unconsciously fabricated. Times Magazine, Slate.com and (ISTSS), once essentially called McNally a liar. “This has nothing to do with gaming or Audubon. Dobbs has published working the system or consciously looking for three books: Reef Madness: A Problematic Diagnosis sympathy,” McNally says. “We all do this: we Charles Darwin, Alexander Agassiz The DSM-IV, the most recent edition (pub- cast our lives in terms of narratives that help us and the Meaning of Coral (Panthe- on, 2005); The Great Gulf: Fisher- lished in 1994), defines PTSD as the presence understand them. A vet who’s having a difficult

men, Scientists and the Struggle to of three symptom clusters—reexperiencing via life may remember a trauma, which may or may s Revive the World’s Greatest Fish- nightmares or flashbacks; avoidance by numb- not have actually traumatized him, and every- d dobbd ery (Island Press, 2000); and The ing or withdrawal; and hyperarousal, evident in thing makes sense.” i Northern Forest, with Richard

irritability, insomnia, aggression or poor con- To make the diagnosis of PTSD more rigor- of dav Ober (Chelsea Green, 1995). His centration—that arise in response to a life- ous, some have suggested that blood chemistry, Neuron Culture blog is at http:// rtesy

scienceblogs.com/neuronculture threatening event [see box above]. brain imaging or other tests might be able to de- Cou

50 Scientific American © 2009 SCIENTIFIC AMERICAN, INC. April 2009 “PTSD is a real thing, without a doubt,” McNally says. “But as a diagnosis, PTSD has become so flabby and overstretched, so much a part of the culture, that we are almost certainly mistaking other problems for PTSD and thus mistreating them.” Ric hard J. McN ally, Harvard University tect physiological signatures of the disorder. give the best treatment, you have to have the Some studies of stress hormones in groups of right diagnosis.” PTSD patients show differences from normal The most effective treatment for patients subjects, but the overlap between the normal whose symptoms arise from trauma is exposure- and the PTSD groups is huge, making individual based cognitive-behavioral therapy (CBT), which Discrepancies profiles useless for diagnostics. Brain imaging concentrates on altering the response to a specific has similar limitations, with the abnormal dy- traumatic memory by repeated, controlled expo- in Diagnoses namics in PTSD heavily overlapping those of de- sure to it. “And it works,” McNally says. “If Estimates of PTSD incidence among pression and anxiety. someone with genuine PTSD goes to the people soldiers are often inflated for several reasons, including the condition’s With memory unreliable and biological mark- who do this really well, they have a good chance vague diagnostic criteria. Assessment ers elusive, diagnosis depends on clinical symp- of getting better.” CBT for depression, in con- survey questions—and answers—

toms. But as a study in 2007 starkly showed, the trast, teaches the patient to recognize dysfunc- are also highly subject to interpreta-

S,” symptom profile for PTSD is as slippery as the tional loops of thought and emotion and develop tion. Stricter analyses of the 1990 OD would-be biomarkers. J. Alexander Bodkin, a new responses to normal, present-day events. “If National Vietnam Veterans Readjust- METH

D ment Survey data, for instance, Y J.Y L. PRICE, N B psychiatrist at Harvard’s McLean Hospital, a depressed person takes on a PTSD interpreta- A

) reduced PTSD incidence to one third A Y,” Y,” T screened 90 clinically depressed patients sepa- tion of their troubles and gets exposure-based UD DA of the original results. graphs

. ( rately for PTSD symptoms and for trauma, then CBT, you’re going to miss the boat,” McNally IBID compared the results. First he and a colleague says. “You’re going to spend your time chasing STMENTST U J

ISITWITH NEW used a standardized screening interview to assess this memory down instead of dealing with the AD V SCIENCE, 1990 National Vietnam RE symptoms. Then two other PTSD diagnosti- way the patient misinterprets present events.” A NSRE

A Veterans Readjustment LLY, IN LLY, NS: A cians, ignorant of the symptom reports, used an- To complicate matters, recent studies show- A Survey (NVVRS) N ETER c V

ETER other standard interview to see which patients ing that traumatic brain injuries from bomb M Survey Population: 1,000 V A .S. Y R. J. M had ever experienced trauma fitting DSM-IV blasts, common among soldiers in Iraq, produce U Suffered PTSD IETN R V at some point after the war (percent) L R,” B FO

A criteria. symptoms almost indistinguishable from PTSD. A N M W O

A Diagnosed with PTSD

TI If PTSD arose from trauma, the patients with One more overlapping symptom set.

A at time of survey (percent) IETN V PTSD symptoms should have histories of trau- “The overlap issue worries me tremendous- LTIES OF OF UA M THEM N S

O ma, and those with trauma should show more ly,” says Gerald M. Rosen, a University of Wash- A R F L RISKSL

A PTSD. It was not so. Although the symptom ington psychiatrist who has worked extensively TRIC C INGS A GIC D 31% 15.4%

O screens rated 70 of the 90 patients positive for with PTSD patients. “We have to ask how we IN L F O PTSD, the trauma screens found only 54 who got here. We have to ask ourselves, ‘What do we 2006 NVVRS

RCES:“ had suffered trauma: the diagnosed PTSD “cas- gain by having this diagnosis?’ ” Data Reanalyses OU es” outnumbered those who had experienced Subtract cases with poorly

ER;“THE PSYCH documented diagnoses ST 18, 2006; “PSYCHI D NSEN;S U R

A traumatic events. Things got worse when Bod- G Disabling Conditions (Dohrenwend et al.) O IS

D kin compared the diagnoses one on one. If PTSD Rosen is thinking of clinicians when he asks

L. 313, AU required trauma, then the 54 trauma-exposed about gain. But what does a veteran gain with a );JEN CHRISTI VO

TICSTRESS patients should account for most of the 70 P TSD - PTSD diagnosis? One would hope, of course, A 18% 9% M

McNally positive patients. But the PTSD-symptomatic that it grants access to effective treatment and AU ( SCIENCE, Subtract cases not suffering

STTR patients were equally distributed among the support. This is not happening. In civilian pop- L.,IN O

A “clinically significant

R P R trauma-positive and the trauma-negative groups. ulations, two thirds of PTSD patients respond impairment” (McNally) FO ET D The PTSD rate had zero relation to the trauma to treatment. But as psychologist Christopher

HarvardNews Office rate. It was, Bodkin observed, “a scientifically Frueh, who researched and treated PTSD for the L CENTERL E HRENWEN A D N DO

O unacceptable situation.” VA from the early 1990s until 2006, notes, “In . B TI

STINI 11% 5.4% A Y U N B J More practically, as McNally points out, “To the two largest VA studies of combat veterans,

www.SciAm.com © 2009 SCIENTIFIC AMERICAN, INC. SCIENTIFIC AMERICAN 51 Distinction neither showed a treatment effect. Vets getting dier gets free lifetime health care. Australian Denied PTSD treatment from the VA are no more likely vets come home to an utterly different support to get better than they would on their own.” system from ours: theirs is a scaffold they can In January the Department of The reason, Frueh says, is the collision of the climb. Ours is a low-hanging “safety net” liable Defense announced that it would PTSD construct’s vagaries with the VA’s disabil- to trap anyone who falls in. not award Purple Hearts to veterans diagnosed with PTSD. The ruling was ity system, in which every benefit seems struc- based partly on a distinction between tured to discourage recovery. Two Ways to Carry a Rifle physical wounds that can be objec- The first benefit is health care. PTSD is by far When a soldier comes home, he must try to rec- tively assessed and psychic suffering the easiest mental health diagnosis to have de- oncile his war experience with the person he was that is more subjective. Divided clared “service-connected,” a designation that beforehand and the society and family he returns public reaction to the decision under- lined the heavy emotional and often means the difference between little or no to. He must engage in what psychologist Rachel cultural significance attached to this care and broad, lasting health coverage. Service Yehuda, who researches PTSD at the Bronx VA diagnosis—and the diagnostic connection also makes a vet eligible for month- Hospital, calls “recontextualization”—the pro- construct’s problems. ly disability payments of up to $3,000. That cess of integrating trauma into normal experi- On one hand, recent neuroscience link may explain why most veterans getting ence. It is what we all do, on various scales, when makes clear that serious mental health disorders reflect brain dysfunction, if PTSD treatment from the VA report worsening we suffer breakups, job losses or the deaths of not actual injury, and it seems only symptoms until they are designated 100 percent loved ones. Initially the event seems an impossi- fair to consider psychic war wounds disabled—at which point their use of VA mental ble aberration. Then slowly we accept the trau- every bit as real as physical ones. At health services drops by 82 percent. It may also ma as part of the complex context that is life. the same time, a lack of sure diagnos- help explain why, although the risk of PTSD Major Matt Stevens recognizes that this ad- tic borders between PTSD and other depressive or anxiety disorders, along from a traumatic event drops as time passes, the justment can take time. Even after two years at with strong evidence that PTSD is number of Vietnam veterans applying for PTSD home, the war still occupies his dreams. Some- overdiagnosed, will make awarding disability almost doubled between 1999 and times, for instance, he dreams that he is doing this medal for the condition an 2004, driving total PTSD disability payments something completely normal—while carrying extremely problematic proposal until to more than $4 billion annually. his combat rifle: “One night I dreamt I was bird- the nature of PTSD gains clarity and science identifies some indisputable Perhaps most disastrously, these payments watching with my wife. When we saw a bird, she biomarkers. —D.D. continue only if you are sick. For unlike a vet would lift her binoculars, and I would lift my ri- who has lost a leg, a vet with PTSD loses disabil- fle and watch the bird through the scope. No ity benefits as soon as he recovers or starts work- thought of shooting it. Just how I looked at the ing. The entire system seems designed to encour- birds.” age chronic disability. “In the several years I It would be easy to read Stevens’s dream as spent in VA PTSD clinics,” Frueh says, “I can’t a symptom of PTSD, expressing fear, hypervig- think of a single PTSD patient who left treat- ilance and avoidance. Yet it can also be seen as ment because he got better. But the problem is demonstrating his success in recontextualizing not the veterans. The problem is that the VA’s his experience: reconciling the man who once disability system, which is 60 years old now, ig- used a gun with the man who no longer does. nores all the intervening research we have on re- Saving PTSD from itself, Spitzer, McNally, silience, on the power of expectancy, and on the Frueh and other critics say, will require a simi- effects of incentives and disincentives. Some- lar shift—seeing most postcombat distress not times I think they should just blow it up and start as a disorder but as part of normal, if painful, over.” But with what? healing. This turnaround will involve, for start- Richard A. Bryant, an Australian PTSD re- ers, revising the rubric for diagnosing PTSD— searcher and clinician, suggests a disability sys- currently under review for the new DSM-V due tem more like that in place Down Under. An to be published in 2012—so it accounts for the Australian soldier injured in combat receives a unreliability of memory and better distinguish- lifelong “noneconomic” disability payment of es depression, anxiety and phobia from true $300 to $1,200 monthly. If the injury keeps him PTSD. Mental health evaluations need similar from working, he also gets an “incapacity” pay- revisions so they can detect genuine cases with- ment, as well as job training and help finding out leading patients to impose trauma narra- work. Finally—a crucial feature—he retains all tives on other mental health problems. Finally, these benefits for two years once he goes back Congress should replace the VA’s disability sys- to work. After that, incapacity payments taper tem with an evidence-based approach that re- Getty Images to zero over five years. But noneconomic pay- moves disincentives to recovery—and even go ng ments—a kind of financial Purple Heart—con- the extra mile and give all combat veterans, in- x Wo x

tinue forever. And like all Australians, the sol- jured or not, lifetime health care. Ale

52 Scientific American © 2009 SCIENTIFIC AMERICAN, INC. April 2009 Recent studies showing that traumatic brain injuries from bomb blasts, common among soldiers in Iraq, produce symptoms almost indistinguishable from PTSD. One more overlapping symptom set.

These changes will be hard to sell in a culture took particular care to tie that resists any suggestion that PTSD is not a symptoms to types of com- ROADSIDE BOMB aftermath in Ramadi, Iraq common, even inevitable, consequence of combat exposure. Among some 12,000 troops who bat. Mistaking its horror for its prevalence, went to Iraq or Afghanistan, 4.3 percent devel- most people assume PTSD is epidemic, ignoring oped diagnosis-level symptoms of PTSD. The all evidence to the contrary. rate ran about 8 percent in those with combat The biggest longitudinal study of soldiers re- exposure and 2 percent in those not exposed. turning from Iraq, led by VA researcher Charles These numbers are about a quarter of the rates Milliken and published in 2007, seemed to con- Milliken found. But they are a close match to firm that we should expect a high incidence of PTSD rates seen in British Iraq War vets and to PTSD. It surveyed combat troops immediately rates McNally calculated for Vietnam veterans. on return from deployment and again about six The contrast to the Milliken study, along with months later and found around 20 percent the consistency with British rates and with Mc- symptomatically “at risk” of PTSD. But of Nally’s NVVRS calculation, should have made those reporting symptoms in the first survey, the Smith study big news. Yet the media, the VA half had improved by the second survey, and and the trauma psychology community almost many who first claimed few or no symptoms completely ignored the study. “The silence,” Mc- later reported serious symptoms. How many of Nally wryly noted, “was deafening.” the early “symptoms” were just normal adjust- This silence may be merely a matter of good ment? How many of the later symptoms were news going unremarked. Yet it supports Mc- the imposition of a trauma narrative onto other Nally’s contention that we have a cultural ob- problems? session with trauma. The selective attention ➥ More To Stevens, for one, is certain these screens are also supports the assertion by military histori- Explore mistaking many going through normal adjust- an and PTSD critic Ben Shephard that Ameri- ment as dangerously at risk of PTSD. Even he, can society itself gained something from the A War of Nerves: Soldiers and Psychiatrists in the Twentieth though functioning fine at work and home and creation of the PTSD diagnosis in the late Century. Ben Shephard. Harvard in society, scored positive in both surveys; he is, 1970s: a vision of war’s costs that, by trans- University Press, 2001. in other words, one of the 20 percent at risk. forming warriors into victims, lets us declare Finally, and weirdly, both screens missed about our recognition of war’s horror and absolves us Progress and Controversy in the 75 percent of those who actually sought coun- for sending them—for we were victimized, too, Study of Posttraumatic Stress Disorder. Richard J. McNally in — seling a finding that raises further doubts fooled into supporting a war we later regretted. Annual Review of Psychology, Vol. 54, about the evaluations’ accuracy. Yet this study We should recognize war’s horror. We should pages 229–252; 2003. received prominent media coverage emphasiz- feel the soldier’s pain. But to impose on a dis- ing that PTSD rates were probably being badly tressed soldier the notion that his memories are Saving PTSD from Itself in DSM-V. undercounted. inescapable, that he lacks the strength to incor- Robert L. Spitzer, Michael B. First and Jerome C. Wakefield inJournal of — A few months later another study the first porate his past into his future, is to highlight Anxiety Disorders, Vol. 21, No. 2, to track large numbers of soldiers through the our moral sensitivity at the soldier’s expense. pages 233–241; February 2007. wars in Iraq and Afghanistan—provided a clear- PTSD exists. Where it exists we must treat it. er and more consistent picture. Led by U.S. Navy But our cultural obsession with PTSD has mag- Posttraumatic Stress Disorder: researcher Tyler Smith and published in the Brit- nified and finally perhaps become the thing it- An Empirical Evaluation of Core Assumptions. Gerald M. Rosen — ish Medical Journal, the study monitored men- self a prolonged failure to contextualize and and Scott O. Lilienfeld in Clinical tal health and combat exposure in 50,000 U.S. accept our own collective aggression. It may be

TERS Psychology Review, Vol. 28, No. 5, U

RE soldiers from 2001 to 2006. The researchers our own postwar neurosis. ■ pages 837–868; June 2008.

The Dawn of Miniature Green Lasers

Semiconductors can generate laser light in all colors except one. But new techniques for growing laser diodes could soon make brilliant full-spectrum displays a reality By Shuji Nakamura and Michael Riordan

n a rainy Saturday morning in January witness a brilliant blue-violet flash emanating 2007, Henry Yang, chancellor of the from a glassy chip of gallium nitride (GaN). OUniversity of California, Santa Barbara, Within days another group of researchers at took an urgent phone call. He excused himself Rohm Company in Kyoto, Japan—a partner in abruptly from a meeting, grabbed his coat and the U.C.S.B. center—duplicated the feat using umbrella, and rushed across the windswept similar materials. Although blue laser diodes are U.C.S.B. campus to the Solid State Lighting and not in themselves very revolutionary [see “Blue- Display Center. The research group there includ- Laser CD Technology,” by Robert L. Gunshor ed one of us (Nakamura), who had just received and Arto V. Nurmikko; Scientific American, the Millennium Technology Prize for creating July 1996], Nichia Chemical Industries (based the first light-emitting diodes (LEDs) that emit in Tokushima, Japan, where Nakamura worked Key Concepts bright blue light. Since that breakthrough over a until 2000), Sony and other companies were still ■ ■ Solid-state lasers can pro- decade earlier, Nakamura had continued his pi- struggling to produce inexpensive GaN laser deduce light in the red and oneering research on solid-state (semiconductor) vices for the Blu-ray disc market. These diodes blue parts of the spectrum lighting, developing green LEDs and the blue la- had previously been fashioned using a method but not the green. ser diodes that are now at the core of modern with stubborn limitations that have kept manu- ■ ■ Recent research suggests Blu-ray disc players. facturing yields down and diode costs high. that this “green gap” As Yang reached the center about 10 minutes The groups from U.C.S.B. and Rohm are de- could be plugged as early later, people were milling about a small test lab. veloping a new way to grow the crystalline lay- as this year. “Shuji had just arrived and was standing there in ers of gallium nitride and related alloys that

■ ■ The advance will allow for his leather jacket asking questions,” he recalled. make up a laser diode. The early successes of the laser-based video displays Nakamura’s colleagues Steven DenBaars and approach not only promise greater yields but that are small enough to James C. Speck were speaking with a few gradu- also buoy hopes of an even bigger payoff: rug- fit in a cell phone. ate students and postdoctoral researchers as ged, compact GaN diodes that emit green laser —The Editors they took turns looking into a microscope. They light—a goal that has long eluded scientists and parted for Yang, who peered into the eyepiece to engineers. The technique should also lead to

54 Scientific American © 2009 SCIENTIFIC AMERICAN, INC. April 2009 high-efficiency green LEDs that emit much more approach, an exceedingly smooth, nanometers- light than existing devices. thin layer of indium gallium nitride (InGaN) is These achievements would fill a gaping void sandwiched between two layers of GaN, form- in the visible spectrum where evolution has ing what is called a heterostructure or quantum trained our eyes to be most sensitive, plugging well [see box on next page]. the “green gap” in the red-green-blue triad need- By applying a suitable voltage, researchers set ed for full-color laser projection and displays. up an electric field perpendicular to these layers They should help speed the introduction of laser that drives electrons and holes—positively projectors for televisions and movie theaters— charged quasiparticles corresponding to the ab- What about which will display much richer colors than other sence of electrons—together within the InGaN Green Laser systems—and of tiny, handheld “pico projec- active layers. Inside this narrow trench, the elec- Pointers? tors” to be used, for example, in cell phones. trons and holes recombine, annihilating one an- And high-power green diodes might even be em- other and generating photons with an energy The green lasers that have long been available employ a complicat- ployed in such diverse applications as DNA se- precisely determined by the properties of the ac- ed two-step process to generate quencing, industrial process control and under- tive semiconductor material. By increasing the light. Semiconductor lasers inside water communications. indium concentration in the alloy, one can lower these devices emit infrared radia- this energy, thereby increasing the wavelength of tion with a wavelength around A New Angle the light and changing its color from violet to 1,060 nanometers. This radiation then pumps a crystal that oscillates The key advance that led to bright blue solid- blue to green. at half this wavelength—about state lighting was the mid-1990s conversion to In LEDs the photons leave the well almost im- 530 nanometers, solidly in the LEDs and laser diodes made of gallium nitride mediately, perhaps rebounding once or twice be- green. The process is costly, ineffi- and its alloys [for a profile of Nakamura, see fore exiting the device or being absorbed in the cient and imprecise—the second “Blue Chip,” by Glenn Zorpette; Scientific other layers. But in laser diodes, which produce crystal can heat up, altering the wavelength of the resultant green American, August 2000]. Before that, most coherent light, the photons stay largely confined light. Laser diodes that generate researchers had focused their efforts on zinc within the trench. Two highly reflective mir- green light directly would avoid

Caspar Benson selenide and related compounds. In the new rors—generally polished crystal surfaces at ei- these problems.

www.SciAm.com © 2009 SCIENTIFIC AMERICAN, INC. SCIENTIFIC AMERICAN 55 The Green ther end of it—recycle the photons back and son’s height— counteract the applied external Gap problem forth inside, further stimulating electron-hole voltage. They pull electrons away from holes— recombination. The laser light generated by this making it harder for them to recombine and yield Scientists have long been able to “stimulated emission” process is a tight pencil light. In effect, the electrons pile up at one side of build semiconductor lasers that beam of exceedingly pure color. the long quantum dance hall and holes at the oth- create light in red parts of the spectrum, and in the past decade To make conventional GaN diodes, workers er, both reluctant to cross over and meet. they have conquered the blue place a thin wafer of sapphire (or, increasingly, Known as the quantum-confined Stark effect, and violet sections as well. Yet as gallium nitride) inside a reaction chamber. There this nagging problem becomes particularly acute they try to push these lasers into hot gases deposit successive layers of gallium, in- as the color of the emitted light shifts from violet the green part of the spectrum, dium and nitrogen atoms on that substrate, with to blue to green. And as the current through the the amount of power produced drops precipitously. the exact proportions of each element varying diode increases, the greater number of charge from layer to layer. The atoms in these layers au- carriers partially blocks the internal electric fields tomatically align with the existing crystalline that keep electrons and holes apart. With these structure, as predetermined by the substrate. fields partially screened out, the electrons and Atom by atom, the layers grow in parallel with holes then recombine at higher energies, shifting what is called the substrate’s c-plane, which is the light toward the blue end of the spectrum.

ower perpendicular to the crystal’s axis of hexagonal These problems are the main reason why green symmetry [see box on opposite page]. laser diodes and high-efficiency green LEDs have Laser P Unfortunately, electrostatic forces and inter- remained but a dream for more than a decade. nal stresses between successive layers of positive- (The familiar green laser pointers used by lectur- ly charged gallium or indium ions and negatively ers have semiconductor lasers that emit infrared charged nitrogen ions create strong electric fields radiation and pump another laser in a complicat-

400 500 600 700 perpendicular to the c-plane. These fields, which ed, inefficient frequency-doubling scheme.) Wavelength (nanometers) can reach up to 100 volts per micron—equivalent The approach pioneered by the U.C.S.B. and to nearly 200 million volts across an average per- Rohm groups attempts to sidestep these prob- [the basics] How Semiconductor Lasers Work Inside a solid-state laser, electrons meet positively charged entities wavelength of this light, scientists must alter the material inside the called holes, annihilating one another and creating light. To adjust the semiconductor. But doing so can lead to other problems.

Positive electrode GaN barrier layer Magnesium- doped GaN Hole

InGaN active layer Silicon-doped GaN Substrate

Negative Electron

electrode );

layer cake INTERNAL AFFAIRS Scientists create a diode laser by depositing layers of semiconduc- Inside these layers, electrons and GaN barrier layer ) tor material on top of an underlying substrate. On the bottom end holes annihilate to produce light (right).

of this semiconductor sandwich, gallium nitride (GaN) is mixed—or The wavelength of this light depends on the graph an ( an — — semiconductorillustrations “doped” with silicon impurities to produce an excess of negative- indium (In) content of the active layer more leads ( ly charged electrons. On the other end, GaN is doped with magne- to longer wavelengths and thus greener light. But the more ameri c

sium to give it an excess of positive charges, or “holes.” A voltage indium in these layers, the more that indium is likely to pool into small etseCk R

across the electrodes sets up an electric field that drives the “islands” during manufacture. The islands can alter the light’s wave- e g

electrons and holes together inside the central active layers. length—an unacceptable flaw in a laser. ientifi c Geor s c

56 Scientific American © 2009 SCIENTIFIC AMERICAN, INC. April 2009 [THE SOLUTION] A New Foundation A substrate is a slice of a crystal, and anything grown on top of it inherits its crystalline structure. The blue diode lasers that power Blu-ray disc players and PlayStation 3 game consoles are usually grown on top of sapphire, which, as substrates go, is relatively cheap and readily available. Yet it is difficult to use these substrates to make green laser diodes. In response, scientists have turned to alternative crystal facets for help.

c-Plane: The Classic cut m-Plane: A costly alternative semiPolar: The compromise Though commonly used for blue lasers, a Two research groups are growing laser diodes A third option is semipolar substrates that are c-plane substrate has drawbacks, such as on a crystal’s m-plane, which cuts across the cut at a 45-degree angle to the crystal axis. inducing electric fields that conspire to keep crystal’s side. Diodes grown on this plane do These substrates also do not produce strong electrons and holes apart. The problem gets not suffer from induced fields, but the sub- fields, and they seem to yield better lasers and worse as the wavelength shifts toward green. strates are more costly than c-plane versions. LEDs than the m-plane substrates do.

lems by starting with a thin wafer of pure, crys- beginning in 2000—including DenBaars and talline GaN that has been sliced along a larger Speck at U.C.S.B. The early devices performed crystal’s m-plane [see box above] and then pol- only modestly, mainly because of the lack of ished. Diodes fabricated on these so-called non- high-quality GaN substrates. In 2006, however, polar substrates do not encounter the problems Mitsubishi Chemical Corporation in Tokyo— ) of conventional polar c-plane devices, because another partner in the U.C.S.B. center—began crystals

( the troublesome fields caused by polarization supplying excellent, low-defect m-plane GaN K C and internal stresses are much lower. substrates to the Rohm and U.C.S.B. research RETSE

E The diodes grown on GaN also produce light groups. Less than a centimeter on a side, the sub- G [The Authors]

EOR more efficiently than ones grown on sapphire be- strates were sliced from small GaN crystals

); G cause they suffer from far fewer crystalline de- about the size of a pencil eraser. Shuji Nakamura is professor in the materials department and

Riordan fects—submicroscopic irregularities and mis- With the new material in hand, Rohm and ( director of the Solid-State Lighting AN

D matches at the interfaces between successive lay- U.C.S.B. fabricated much more efficient LEDs and Energy Center at the Universi-

RIOR ers. Such defects act as centers where electrons in late 2006, and by early 2007 these groups be- ty of California, Santa Barbara. He and holes recombine to produce unwanted heat gan trying to make the more challenging laser was awarded the 2006 Millennium ONNA D instead of light. They can easily propagate up- diodes. On that rainy Saturday morning of Jan- Technology Prize for his work on Y OF ward through the successive diode layers during uary 27, U.C.S.B. graduate student Matthew blue laser diodes and LEDs. RTES

U Michael Riordan teaches the

O the growth process (in what are called threading Schmidt went to the lab to finish the last fabrica- history of physics and technology ); C dislocations) and reach the active layers. The tion step. Then he took the diode over to the at Stanford University and at the presence of these defects played havoc with pro- nearby test lab and hitched it up to a power sup- University of California, Santa Nakamura ( duction yields when Nichia and Sony first tried ply. Suddenly, as he cranked up the current flow- Cruz. He is co-author of Crystal to manufacture blue laser diodes. Because a ing through the diode, a narrow beam of blue- Fire: The Invention of the Transis- tor and the Birth of the Informa- GaN substrate will generate nowhere near as violet light shot out of it. tion Age (W. W. Norton, 1997). many mismatches as sapphire does with the “Wow!” Schmidt thought. “I can finally next-above layer of GaN or one of its alloys, di- graduate!” odes grown on nonpolar GaN substrates can He called his thesis adviser DenBaars, who at therefore produce much more light—and have first thought he was joking but soon alerted the University of California, Santa Barbara Santa California, of University B correspondingly less heat to dispose of. rest of the group and Chancellor Yang. They ar- AM First suggested in the late 1990s, the non rived within minutes to observe the surprising DY L DY

RAN polar technique was attempted by several groups results. This first nonpolar GaN laser diode op-

www.SciAm.com © 2009 SCIENTIFIC AMERICAN, INC. SCIENTIFIC AMERICAN 57 [The Applications] erated at a wavelength of 405 nanometers (nm), as did the first Rohm device a few days later. And H a n d h e l d P r o j e c t o r s the currents flowing through these diodes were The smallest currently available handheld projectors are about the size of a remote con- only two to three times what was then being trol and use LEDs to generate light. By the end of this year the first laser-based models achieved in commercially available devices made should go on sale. Even though they use frequency-doubling technology to create green by Nichia and Sony, indicating that any heating laser light, they will produce high-resolution, richly colored images. Future models that problems were manageable. rely on green laser diodes will allow for brighter and more efficient displays, and they will also shrink the projectors enough to allow them to fit inside your cell phone. Going for Green Here is a look at two laser-based prototypes currently in development and After that breakthrough, the U.C.S.B. group a few LED projecters out now. —The Editors decided to drop most of its work on polar diodes and focus on nonpolar ones. It also began inves- Microvision Show WX  tigating a related strategy based on “semipolar” Inside this laser-projector protype, red, GaN substrates, which are wafers cut at an angle blue and green lasers focus onto a single of about 45 degrees to a crystal’s major axis [see mirror about the size of a pinhead. As light bounces off that reflector, the mirror box on preceding page]. Diodes fabricated on assembly rapidly scans back and forth to project semipolar substrates also have much less intense pixels one by one onto a screen or wall. The lack of internal electric fields than polar diodes do, lenses means the projector never needs to be focused. though not as low as in nonpolar diodes. The Resolution: 848 × 480 pixels (DVD-equivalent) U.C.S.B. researchers hope that one of these Available: Later this year geometries will allow them to create the first green laser diodes and to make high-power Light Blue Optics LEDs at even longer wavelengths. Rohm has The start-up Light Blue Optics is also working on a laser projector. These devices use forged ahead in these areas, too, concentrating liquid crystal on silicon (LCOS) chips that contain thousands of tiny liquid-crystal its efforts on nonpolar substrates. windows. The chip opens and closes these pixels in rapid succession to let light through The new substrates, however, are not suffi- and form an image. The company plans to have a laser-projection system ready for cient on their own to get beyond blue. Green di- delivery to third-party manufacturers by the start of next year. odes require adding more indium to the InGaN Resolution: 854 × 480 pixels Available: 2010 active layer, but the extra indium exacerbates internal stresses and disrupts the crystalline struc- 3M MPro110  ture. It increases the number of crystal defects, When it debuted in 2008, the LED-based MPro110 was the which in turn reduces the light output and gen- first handheld projector to go on sale in the U.S. Although it erates excess heat. While LEDs can still function is a bit larger than the Samsung MBP200 (below), this LCOS despite the added defects, their efficiencies plum- projector can display television-quality video. 3M is licensing an met as the color shifts from blue to green. Laser updated version of the technology that powers the MPro110 for diodes are even more finicky and cannot tolerate use in other applications, such as cell phones. so many defects. The highest wavelength thus Resolution: 640 × 480 pixels (equivalent to standard-definition TV) far achieved in a laser diode is 488 nm, in the Price: $359 blue-green (or cyan) part of the spectrum. Samsung MBP200 Pico Projector Layers of InGaN must also be grown at substantially lower temperatures—about 700 This LED-based projector uses a miniaturized version of the digital light degrees Celsius versus 1,000 degrees C for projection (DLP) chip from Texas Instruments. Light from a white LED first passes through a rapidly changing color wheel. It the GaN layers around it—to prevent the then hits an array of thousands of mirrors. Each mirror is indium atoms from dissociating from the about one-fifth the width of a human hair and switches other atoms. Such dissociation can form areas on and off thousands of times a second. Reflected light of inhomogeneous indium alloys, or “islands,” from this mirror forms the pixels that make up an image. which in turn causes the electron-hole recombi- Resolution: 480 × 320 pixels (approximately equivalent nation energy to vary from point to point. That to a smart phone) variation makes the emission spectrum too Available: Later this year broad to yield the coherent, monochromatic light expected from a laser. Thus, when workers Toshiba LED pico Projector  raise the reactor temperature to grow the next This LED competitor also uses the DLP chip technology. GaN layer atop the delicate InGaN layer just de- Resolution: 480 × 320 pixels posited, they must be especially careful so as not Price: $399 to form too many of these islands. But the pro-

58 Scientific American © 2009 SCIENTIFIC AMERICAN, INC. April 2009 cess gets ever more difficult as the indium con- Suddenly, as block to large-scale manufacture of nonpolar centration increases. and semipolar GaN laser diodes and LEDs— The problems are exacerbated in polar di- Schmidt cranked whether violet, blue, green or yellow—is the odes, in which the strong internal fields have led up the current availability of large enough substrates at accept- manufacturers to create active layers of InGaN able costs. So far Mitsubishi has supplied GaN that are exceedingly thin—less than 4 nm, or flowing through substrates about a square centimeter in surface only about 20 atoms thick. This approach helps the diode, a area that are sliced from small crystals, but the to keep electrons and holes huddled closer to- wafer area needs to increase nearly 20-fold. gether, boosting the chances that they will meet narrow beam To produce laser diodes economically, man- and mate to create light. Because nonpolar and of blue-violet ufacturers must have substrates at least five cen- semipolar diodes have internal electric fields that timeters in diameter costing about $2,000 per are almost negligible, however, their InGaN ac- light shot out wafer, says Robert Walker, a semiconductor in- tive layers can be grown substantially thicker— of it. “Wow!” he dustry expert at Sierra Ventures in Menlo Park, up to 20 nm. The indium islands still form in Calif. To manufacture the simpler (and much these more robust layers, but they are thought to thought. “I can cheaper) LEDs, he adds, substrate costs must occur closer to the interfaces with the surround- finally graduate!” drop by another order of magnitude. And these ing GaN. Confining the islands there should LEDs will still have to compete with advanced boost the chances of getting the narrower light blue and green LEDs, such as those introduced spectrum needed for laser action. And the thick- in late 2007 by CREE Research in Durham, er, more robust active layers help to simplify N.C. (also a partner in the U.C.S.B. center), manufacturing in other ways, allowing the elim- which fabricates its devices on silicon-carbide ination of extra “cladding” layers in the diode substrates.

) stack, which had formerly been added to help Mitsubishi is now streamlining and scaling trap and guide the photons. up its existing fabrication procedure in a move Since the breakthrough demonstration in toward commercializing nonpolar GaN sub- LED Pico Projector

( January 2007, the U.C.S.B. and Rohm groups strates. According to Kenji Fujito, who devel- A B I

H have been steadily pushing back the frontiers of oped the methods used to grow nonpolar GaN

TOS the new technology, publishing new results al- substrates, it is a sluggish and painstaking pro-

Y OF most every month. In April 2007, for example, cess. At present, Mitsubishi can produce just RTES U

O U.C.S.B. reported a nonpolar LED emitting enough nonpolar (or semipolar) GaN substrates

); C blue-violet light at 402 nm that achieved quan- to meet the research needs of Rohm and U.C.S.B. tum efficiencies—the ratio of photons emitted Fujito says it will be at least another year or two MBP200 G (

N to electrons flowing in—above 45 percent. This before they can produce substrate wafers five U figure represented a 100-fold improvement in centimeters in diameter. Walker concurs, pro- SAMS these devices in just a year. Several months later jecting that it should take a few years before non- Y OF the group reported semipolar green LEDs that polar substrates will be economically available, RTES U O operated as high as 519 nm, with efficiencies either from Mitsubishi or other substrate suppli- ); C close to 20 percent. (Unfortunately, these diodes ers, such as Kyma Technologies in Raleigh, N.C.

MPro110 experienced substantial blue shifts, for reasons But U.C.S.B.’s DenBaars expects commercial C. ( that remain obscure.) nonpolar diodes to be manufactured sooner, cit- , IN M

3 More recently, U.C.S.B. fabricated yellow ➥ More To ing the higher yields and thus lower overall costs

Y OF semipolar LEDs operating at 563 nm with effi- Explore that these substrates should allow. RTES

U ciencies above 13 percent. These were the first In the meantime, lab work will continue to O The Blue Laser Diode: The Com- ); C efficient yellow LEDs made with GaN and its plete Story. Second edition. Shuji lead the way. Both the Rohm and U.C.S.B. alloys. Nonpolar laser diodes have also begun Nakamura, Stephen Pearton and groups, as well as several others, have set their Show WX Gerhard Fasol. Springer, 2000.

C. ( to approach the performance of their polar sights on achieving the first successful green laser

, IN counterparts. In May 2008 Rohm reported diodes. And in September 2008 U.C.S.B. report- New GaN Faces Offer Brighter ISION V achieving nonpolar laser diodes that operated Emitters. Robert Metzger in ed observing stimulated emission at cyan (480 RO C at wavelengths as high as 481 nm —approaching Compound Semiconductor, Vol. 12, nm) and green (514 nm) wavelengths from non- MI the record of 488 nm held by polar diodes. No. 7, pages 20–22; August 2006. polar and semipolar GaN diodes that had been Y OF

RTES optically pumped with light from another laser. U

O Non-polar GaN Reaches Tipping

: C The Big Time Getting similar emissions using electric current E

G Point. Steven DenBaars, Shuji But fabricating a device in the laboratory is not to drive the diodes instead should not be too far PA Nakamura and Jim Speck in the same as being able to manufacture it in com- Compound Semiconductor, Vol. 13, off. We would not be surprised to see one or both

OPPOSITE mercial quantities. Probably the biggest road- No. 5, pages 21–23; June 2007. of these groups succeed later this year. ■

Preventing the Next Pandemic An international network for monitoring the flow of viruses from animals to humans might help scientists head off global epidemics By Nathan Wolfe

weat streamed down my back, thorny As the chimps feasted on the monkey’s raw Key Concepts shrubs cut my arms, and we were losing flesh and entrails, I thought about how this them again. The wild chimpanzees my scene contained all the elements of a perfect ■ ■ Most human infectious S colleagues and I had been following for nearly storm for allowing microorganisms to jump diseases originated in animals. five hours had stopped their grunting, hooting from one species to the next, akin to space trav- and screeching. Usually these calls helped us elers leaping at warp speed from one galaxy to ■ ■ Historically, epidemiolo- follow the animals through Uganda’s Kibale another. Any disease-causing agent present in gists have focused on Forest. For three large males to quiet abruptly that monkey now had the ideal conditions un- domestic animals as the surely meant trouble. Suddenly, as we ap- der which to enter a new type of host: the chimps source of these scourges. But wild animals, too, have proached a small clearing, we spotted them were handling and consuming fresh organs; transmitted many diseas- standing below a massive fig tree and looking their hands were covered with blood, saliva and es to us, including HIV. up at a troop of red colobus monkeys eating and feces, all of which can carry pathogens; blood playing in the treetop. and other fluids splattered into their eyes and ■ ■ To address the threat

The monkeys carried on with their morning noses. Any sores or cuts on the hunters’ bodies ) posed by wild animals, researchers are studying meal, oblivious to the three apes below. After could provide a bug with direct entry into the the microbes of these appearing for a moment to confer with one an- bloodstream. Indeed, work conducted by my

other, the chimps split up. While the leader crept group and others has shown that hunting, by photoillustration creatures and the people ( EN toward the fig tree, his compatriots made their animals such as chimpanzees as well as by hu- S

who come into frequent N A TI

contact with them. way up two neighboring trees in silence. Then, mans, does provide a bridge allowing viruses to S RI H

in an instant, the leader rushed up his tree jump from prey to predator. The pandemic form C ■ ■ Such monitoring may EN J enable scientists to spot screaming. Leaves showered down as the mon- of HI V began in this way, by moving from mon- emerging infectious keys frantically tried to evade their attacker. But keys into chimpanzees and, later, from chim- diseases early enough the chimp had calculated his bluster well: al- panzees into humans. GettyImages; to prevent them from though he failed to capture a monkey himself, Today HIV is so pervasive that it is hard to becoming pandemics. one of his partners grabbed a juvenile and made imagine the world without it. But a global pan-

his way down to the forest floor with the young demic was not inevitable. If scientists had been Scientificrd —The Editors o

monkey in tow, ready to share his catch. looking for signs of new kinds of infections in Oxf

60 Scientific American © 2009 SCIENTIFIC AMERICAN, INC. April 2009 DANGER: Wild animals can carry pathogens capable of jumping into humans— the first step toward becoming a major infectious killer—so a new plan for avoiding pandemics begins with them.

www.SciAm.com © 2009 SCIENTIFIC AMERICAN, INC. SCIENTIFIC AMERICAN 61 the the local fauna, just as my friends in New Jersey out the world have done for he millennia: hunts rare here. And so he does what humans through monkey. But those forms ofprotein are animal very well might prefer villagers pork or beef to and system tissues. hunter’s circulatory the to access have now baboon’sblood the in open cuts along the way. agents Any infectious own sweat and drips down his leg, flowinginto travels, the blood from his prey mingles with his to go before he reaches his village. As the hunter ed the foranimal some miles and still has more he as shorts his back a baboon. He 50-pound has transport cotton simple walks barefoot only along a forest path, on carrying wears hunter The day. his about going hunter bushmeat typical consider a are populations vulnerable, African high risk particularly of infection. and we that people these would suspected be at populations, human into entering were HIV were trying to determine whether new strains of er wild animals, as well as keep them as pets. We Afri can of country who Cameroon Central hunt and the butch in villagers rural in viruses of a study 10we ago, when initiated years began Our surveillance vision grew out of research we Stalking Viruses before they start. stop pandemics to needed warning early the provide may ping the bugs’ activity. We believe such eavesdrop for or ofsigns in changes new microorganisms them with contact frequent into come who ple peo the and animals to new plan wild monitor bold a developed recently I and colleagues my strains of influenza.In response tothese threats, the case of and virus Japanese encephalitis some in as to us, then and ones to domestic animals as did HIV, or indirectly, by passing from wild whether they come fromdirectly wild animals, quickly, more pandemic become to diseases new allows travel, air and road by extensively connectedness of human populations, linked so a to few. name Ebola, vast inter today the And and dengue SARS, influenza, including mals, ani in originated present, and past diseases, infectious of human half More than reservoir. is not alone in having emerged from an animal to intervene and mitigate the virus’s spread. HIV that, epidemiologists might well af have been able had it before long flicted it millions ofpeople. With a about head startlike known have could they 1970s, and 1960s the in back Africans 62 If If the hunter had his choice, he and his fellow To understand why we thought these Central

Scientific Americ a n

------tries in Africa and Asia. and Africa in tries coun 11 in projects health public and research active has currently Wolfe Award, Explorer Emerging National Geographic Society’s Director’s H Pioneer of Award and the Institutes National the U infectious diseases from doctorate in immunology and Initiative. casting Fore Viral Global the of director Stanford at gy H in Professor Visiting Wolfe Nathan [Th niversity in 1998. A recipient of of recipient A 1998. in niversity likely emerged. they which from and the animals 10 at lists the right diseases such The table to of those livestock. in addition of creatures, wild crobes mi the monitor to need the scores under fact This animals. wild from to are have believed come of humans diseases of Many infectious the major Wild Animals Diseases from Infectious [C e Au O NTEXT] © 2009 SCIENTIFIC AMERICAN, INC. AMERICAN, © SCIENTIFIC 2009 t ho U is Lorry I. Lokey r niversity and and niversity ] H e earned a e earned uman Biolo uman H arvard ealth ealth - - -

per per we gave them. obtain these samples by using pieces of filterpa to prey. them on We their relied from samples blood we needed activities, hunting and health and peppering them with questions about their tion to drawing samples of their addi blood in for study essential: was cooperation Their data. collecting begin we could trust their gaining after Only game. their seize to going were we that was not easy.project feared Many on this more distantly. than is a deer, which is related to humans much hunter to the microorganisms other and ruses vi its transfer to likely more is quarry primate Cen the that own survival and are that of his family and that his his for food this on perhaps, relies hunter African tral differences, only The party. dinner venison annual their for ration prepa in season, deer during farm do on their tracted gorilla SFV. gorilla tracted rarely pursued by subsistence hunters gorillas butchered and hunted ing hav reported who man 45-year-old a example, telling one particularly In populations. hunter We found had that all variants three entered the bug. ofthe variant distinctive genetically own its harbors species primate these of each and gorillas, and mandrills monkeys, guenon ing is SFV belongs. native to includ most primates, es of virus family it and of same is a the member Lancet, we infirstreported apaper publishedin in 2004 not previously seen in humans. One agent, which and the hunted viruses revealed several animal

- - — Persuading Persuading the villagers to cooperate with us Our analyses of the blood from the hunters hunters the offrom blood the analyses Our

the so-called retroviruses

is known as simian foamy (SFV), virus Chagas’ disease fever Yellow sleeping sickness West African malaria Vivax sleeping sickness African East Dengue fever Plague Influenza A H AIDS D epatitis epatitis B isease

mammals and domestic wild Many African primates ruminants Wild and domestic Asian macaques ruminants Wild and domestic O Rodents Wild birds Apes Chimpanzees Sou — ld World primates to which HIV HIV which to rce April 2009 — — had con had animals ------

courtesy of tom clynes (Wolfe) [Stages to watch] From Animal Microbe to Human Pathogen The process by which a pathogen of animals evolves into one exclusive to humans occurs in five stages. Agents can become stuck in any of these stages. Those in early stages may be very deadly (Ebola, for example), but they claim few lives overall because they cannot spread freely among humans. The better able a virus is to propagate in humans, the more likely it is to become a pandemic.

Disease Examples: Reichenowi malaria Rabies Ebola Dengue HIV

Stage 1: Pathogen is present in animals but has not been detected in humans under natural conditions.

Stage 2: Animal pathogen has been transmitted to humans but not between humans.

Stage 3: Animal pathogen that can be transmitted between humans causes an outbreak of disease but only for a short period before dying out.

Stage 4: Pathogen exists in animals and undergoes a regular cycle of animal-to-human transmission but also sustains long outbreaks arising from human-to-human transmission.

SOURCE: “Origins of Major Human Infectious Diseases,” by Nathan D. Wolfe, Claire Panosian Dunavan and Stage 5: Pathogen has become exclusive to humans. Jared Diamond, in Nature, Vol. 447; May 17, 2007

In those same Central African populations spontaneously. But the fact that SFV and HTLV we also found a variety of retroviruses known TWO-WAY are in the same family as HI V, which did spawn as human T lymphotropic viruses (HTLVs), so STREET a global epidemic, means that epidemiologists named because of their propensity for infecting must keep a close eye on them. immune cells called T lymphocytes. Two of the My colleagues and I have outlined five stages HTLVs, HTLV-1 and HTLV-2, were already in the transformation of a pathogen of animals well known to affect millions of people around into one that specializes on humans. In stage 1, the world and contribute to cancer and neuro- the agent lives only in animals. In stage 2, it can ) logical disease in some infected individuals. But be transmitted to a human only from an animal. HTLV-3 and HTLV-4, which we described in A stage 3 germ is transmitted primarily from an- illustration (

AS 2005 in the Proceedings of the National Acad- imals to humans, but it can also spread among M Pathogens do not jump only

HO emy of Sciences USA, were new to science. Giv- humans for a short time before dying out. Once from animals into humans—they

SSA T en the high degree of genetic similarity between the agent reaches stage 4, it can sustain longer can also travel in the other direc- HTLV-3 and its simian counterpart, STLV-3, it outbreaks among humans. By the time it attains ); MELI tion. Some infectious diseases appears as if this virus was picked up through that people have transmitted, stage 5, it has become an exclusive pathogen of hunting STLV-3-infected monkeys. The origin and continue to transmit, to humans and no longer utilizes an animal host. herder in Italy in herder ( of HTLV-4 remains unclear, but perhaps we animals include: Pathogens in stage 4 or stage 5 have the poten- will find its primate ancestor as we continue to tial to cause massive human die-offs. ■■ Tuberculosis (cattle) explore these viruses in monkeys. We do not yet GettyImages t t know whether SF V or the new H TLVs cause ill- ■■ Yellow fever Forecasting the Next Pandemic

hwos ness in people. Viruses do not necessarily make (South American monkeys) Had we been watching hunters 30 years ago, we their hosts sick, and viruses that do sicken peo- might have been able to catch HIV early, before ■■ Measles (mountain gorillas) ple and even spread from person to person do it reached the pandemic state. But that moment ■■ Wilfried Krecic Wilfried not always cause pandemics; often they retreat Poliomyelitis (chimpanzees) has passed. The question now is, How can we

www.SciAm.com © 2009 SCIENTIFIC AMERICAN, INC. SCIENTIFIC AMERICAN 63 [PREVENTION PROPOSAL] Building a Surveillance Network By monitoring microorganisms in wild animals and the people who are frequently exposed to them, scientists may be able spot an emerging infectious disease before it becomes widespread. To that end, the author recently organized the Global Viral Forecasting Initia- tive (GVFI), a network of 100 scientists and public health officials in six countries (red and orange dots) who are working to track potentially dangerous agents as they move from animals into human populations. The GVFI focuses on tropical regions (green) in particular, because they are home to a wide variety of animal species and because humans there commonly come into contact with them through hunting and other activities. Eventually the GVFI hopes to expand the network to include more countries with high levels of biodi- c o u n t r y : Cameroon versity, some of which are shown here (yellow dots). v i r u s e s p r e v i o u s ly s p a w n e d : HIV s e n t i n e l p o p u l a t i o n u n d e r s t u d y f o r n e w p a t h o g e n s : People who hunt and butcher wild animals

c o u n t r y : Democratic Republic of the Congo v i r u s e s p r e v i o u s ly s p a w n e d : Primary study site (human and animal testing) Tentative site for future study Marburg, monkeypox, Ebola Secondary study site (animal testing only) Tropical region s e n t i n e l p o p u l a t i o n : People who hunt and butcher wild animals

prevent the next big killers? Once my colleagues works to document the full range of viruses, and I had determined that we could study bacteria and parasites that are crossing over remote populations effectively, we knew we from animals into humans. could extend our work more broadly to listen in Though still a fledgling effort, the GVFI now ) on viral “chatter”—the pattern of transfer of has around 100 scientists following sentinel

animal viruses to humans. With global surveil- populations or animals in Cameroon, China, illustration (

lance, we realized, we might be able to sound the Democratic Republic of the Congo, Laos, AS M HO

the alarm about an emerging infectious disease Madagascar and Malaysia—all hotspots for T

before it boils over. emerging infectious diseases. Many of the sen- SSA

TAKING ACTION MELI

Fortunately, through partnership with tinels are hunters, but we are also screening oth- ); If investigators find signs that Google.org and the Skoll Foundation we were er populations at high risk of contracting dis- an emerging pathogen has spread able to launch the Global Viral Forecasting eases from wildlife, such as individuals who beyond humans who have direct

Initiative (GVFI), a program in which ��epidemi- work in Asia’s “wet markets,” where live ani- contact with animals into the );

ologists, public health workers and conserva- mals are sold for food. workers in DRC market mainstream population, they ( will sound an alarm. Protecting tion biologists the world over collaborate to Finding a new microorganism in a hunter is the blood supply will be one identify infectious agents at their point of origin only the first step in tracking an emerging patho- AP Photo important step toward preventing a m and to monitor those organisms as they bubble gen, however. We must then determine whether Cameroon in hunter a pandemic. This measure will up from animals into humans and flow outward it causes disease, whether it is transmissible from require rapid development and Zuyd a n deployment of a diagnostic test from there. Instead of focusing narrowly on just person to person, and whether it has penetrated lf v ha lf nn ( a nn Amm a rl K for the germ. viruses or a particular disease du jour, the GVFI urban centers, where the high density of occu- Sc

64 Scientific American © 2009 SCIENTIFIC AMERICAN, INC. April 2009 THE THREAT ority would be to determine the agent’s mode of FROM PETS transmission, which would inform tactics for blocking its spread. If an agent were sexually transmitted, for example, public health officials could launch awareness campaigns urging con- dom use, among other precautions. Governments can also take measures to keep new viruses from entering the blood banks in the first place. In fact, following our discoveries concerning the relation between exposure to primates and these new viruses, the Canadian Wild animals and farm animals c o u n t r y : China are not the only potential sources v i r u s e s p r e v i o u s ly s p a w n e d : SARS, H5N1 government modified its blood donation poli- s e n t i n e l p o p u l a t i o n : “Wet market” workers cies to exclude donors who have had contact for the next major pandemic. with nonhuman primates. Fido and Fluffy—and other pets, too—could harbor pathogens In addition to our forecasting efforts, the devastating to humans. This new science of pandemic prevention includes possibility arises when pets come programs such as HealthMap and ProMED, into contact with germ-carrying which compile daily reports on outbreaks wild animals. The germs can jump around the world, and cutting-edge cyberwarn- into pets, which can then transmit these agents to their owners. ing systems such as those piloted by Google.org to use patterns in search engine data to success- fully forecast influenza. Likewise, national and international surveillance and response systems of local governments and the World Health Or- ganization will play an important role in stop- ping the next plague. For our part, we would ultimately like to expand our surveillance network to more coun- ➥ More To tries around the world, including such nations as Explore Brazil and Indonesia, which have a tremendous diversity of animal species that could transmit Naturally Acquired Simian Retro- c o u n t r y : Malaysia virus Infections in Central African v i r u s e s p r e v i o u s ly s p a w n e d : Nipah pathogens to humans. Fuller development of the Hunters. Nathan D. Wolfe s e n t i n e l p o p u l a t i o n : Wildlife hunters GVFI will be expensive: building out our net- et al. in Lancet, Vol. 363, No. 9413, work so that we have adequate staff and lab fa- pages 932–937; March 20, 2004. pants could fuel its spread. The appearance in an cilities for testing the sentinel populations every urban center, away from the original source, six months and testing the animals with which Emergence of Unique Primate T-Lymphotropic Viruses among would be a particularly worrisome sign of pan- these people are in contact will cost around $30 Central African Bushmeat Hunt- demic potential. million, and keeping it running will cost another ers. Nathan D. Wolfe et al. in Proceed-

); In the cases of HTLV-3 and HTLV-4, we are $10 million a year. But if it succeeds in averting ings of the National Academy of beginning to study high-risk populations in cit- even a single pandemic within the next 50 years, Sciences USA, Vol. 102, No. 22, ies near hotspots for emerging infectious dis- it will more than pay for itself. Even just mitigat- pages 7994–7999; May 31, 2005.

hunter in Malaysia ease, regularly testing them for these viruses. In- ing such an event would justify the cost.

( Bushmeat Hunting, Deforestation, dividuals with sickle cell disease who receive Humans work to forecast a variety of very and Prediction of Zoonotic Corbis i

h routine blood transfusions for their condition complex natural threats. We rarely question the Disease Emergence. Nathan D. c a

m are one such population that could become in- logic behind trying to predict hurricanes, tsuna- Wolfe et al. in Emerging Infectious No i fected early on. If we find people in these popu- mis, earthquakes and volcanoes. Yet we really Diseases, Vol. 11, pages 1822–1827;

osh December 2005.

uy lations who are infected, we would work to ini- have no reason to believe that predicting pan- ) az dog ); K ); ( tiate worldwide monitoring of blood supplies, demics is inherently harder then predicting tsu- Origins of Major Human Infectious to protect blood recipients. To that end, we are namis. Given the enormous sums of money re- Diseases. Nathan D. Wolfe, Claire Panosian Dunavan and Jared wet market wet working with our long-term collaborator Bill quired to stop pandemics once they have already ( Getty Images Diamond in Nature, Vol. 447, k Switzer and our colleagues at the U.S. Centers been established, it only makes sense to spend a ic w Reuters pages 279–283; May 17, 2007. r

a for Disease Control and Prevention to develop portion of those public health dollars on stop- eung asB new diagnostic tests to check for the presence of ping them in the first place. The ounce of preven-

Ch The Global Viral Forecasting Initiative m

Kin ■ Tho viruses in the blood supply. Another urgent pri- tion principle has never been more apt. Web site: www.gvfi.org

Subscriber alert! Human Mysteries ■ Mathematical Mysticism ■ Resistance of the Real Scientific American has BYBy MICHELLEMichelle PRESSPress been made aware that ■➜ LUCY’S LEGACY: THE QUEST tion the oft-cited view that human evolution some subscribers have FOR HUMAN ORIGINS should have slowed down as culture increas-increas- by Donald C. Johanson and Kate Wong. ingly buffered humans against natural selec-selec- received notifications/ Harmony, 2009 ($25) tion.” Conversational, knowledgeable, flflowing owing subscription offers logically from one topic to the next, the book In 1974 paleontologist Donald is packed with information of the kind that will from companies such C. Johanson found a female be especially intriguing to general readers. as United Publishers skeleton 3.2 million years old that exhibited both ape and ■➜ NAMING INFINITY: A TRUE STORY Network, Global human characteristics. Johan-Johan- OF RELIGIOUS MYSTICISM Publication Services, son and Kate Wong (who is an AND MATHEMATICAL CREATIVITY editor at this magazine) by Loren Graham and Jean-Michel Kantor. Publishers Access recount the stunning discov-discov- Harvard University Press, 2009 Service, Lake Shore ery of Lucy, and then they venture far beyond ($25.95) that to bring readers up-to-date on what has Publishers Service, been unearthed since and the implications Granted, the history of set Publishers Consolidated, of these new fifinds nds for what it means to be theory does not sound like the human. Right up to such current issues as most promising material for a Platinum Publishing speculation about mating between Nean-Nean- good read. Oh, but it is. In the Service, Publishers dertals and Homo sapiens: “Indeed, I believe early 20th century several that Neandertals and moderns were so leading Russian mathemati-mathemati- Service Center and distinct from one another in their physical cians were members of a heret-heret- American Consumer appearance, hunting behavior, language, ical sect called Name Worshipping. In this dress, customs, and so on that they would not practice, repetition of the name of God in-in- Publishing Association. have interbred.” And about whether we are duced a mystical state that, according to the These are not authorized still evolving: “Although the levels of change authors (an American historian of science and are relatively small and do not signal impend-impend- a French mathematician), helped these schol-schol- representatives/agents ing speciation in Homo, they do call into ques-ques- ars to achieve a breakthrough in the develop-develop- of Scientific American. Please forward any EXCERPTExcerpt correspondence you ■➜ SIMULATIONSimulation ANDand ITSIts DISCONTENTSDiscontents may receive from these by Sherry Turkle. MIT Press, 2009 ($22)

companies to: Turkle, founder of the Initiative on Technology and Self at M.I.T., examines the role computer simulation has played in science over the past 25 years. She looks at both what it offers and what it closes off as a younger generation “scrambles to capture their mentors’ tacit knowledge of Christian Dorbandt buildings, bodies, and bombs”: Scientific American “When nuclear testing moved underground, it became easier for weapons designers to dis-distance themselves from the potential consequences of their art. Hidden, the bomb became more 415 Madison Ave. abstract. But even underground testing left craters and seismic convulsions. It scarred the land-land- New York, NY 10017 scape. Now, with explosions taking place on hard drives and in virtual reality chambers, how much harder will it be for weapons scientists to confront the destructive power of their work and its ethical implications? One weapons designer at Livermore laments that he has only once expe-experienced ‘physical verifiverification’ cation’ after a nuclear test. He had ‘paced off the crater’ produced by the blast. It changed him forever. His younger colleagues will not have that.”

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067_Placed.indd 1 2/24/09 2:17:04 PM ask the experts ■ ■ ■ ■ www.SciAm.com/asktheexperts

If galaxies are all moving apart at ever increasing speed, how can they collide? —J. Gow, Fairfax, Va.

Cosmologist Tamara Davis, a research fellow at the University Like revelers on a ship, the galaxies in our group will contin- of Queensland in Australia and an associate of the Dark Cosmolo- ue to collide and interact in myriad interesting ways, but we will gy Center in Denmark, brings together an answer: be forever separated from the revelers on other ships sailing away The dynamics of the universe are governed by competing forc- from us in the vast universe. es whose influence varies with scale, so local forces can override universal forces in discrete regions. On scales larger than galaxy clusters, all galaxies are indeed moving apart at an ever increas- If normal body temperature is ing rate. The mutual gravitational attraction between two galaxies at that distance is too small to have a significant effect, so the about 98 degrees Fahrenheit, galaxies more or less follow the general flow of the expansion. why do we feel hot at that air But it is a different story in a galaxy’s local neighborhood. There temperature? —S. Meyer, Melbourne, Fla. the gravitational attraction can be very significant and the interactions much more exciting. Jeffery W. Walker, a physiology professor at the University of Dark energy, believed to be causing the acceleration of the ex- Arizona, has a cool explanation: pansion of the universe, provides a constant outward force that The human body is like an engine that continuously generates does not dilute as the universe expands. Pitted against this re- large quantities of heat, and its radiator, so to speak, disperses lentless push is the gravitational pull from the rest of the matter heat least effectively in hotter climes. and energy in the universe. Early on, the universe was much Heat is an unavoidable by-product of the work being done by denser than it is today, and the attractive force of gravity was the tissues of the body. Contracting muscles of the heart, dia- winning the battle, on scales both large and small. Clouds phragm and limbs; ion pumps that maintain the elec- of gas condensed to form stars and galaxies, and galax- trical properties of nerves; and biochemical reac- ies drew together to form clusters. If there had been tions that break down food and synthesize new more matter around, the universe might have started to tissues (to name a few) generate body heat contin- recollapse before it ever had the chance to accelerate. uously. With this gurgling volcano of active inter- But matter and energy do dilute as the volume of the nal organs, the body has a critical need to dissi- universe increases, so dark energy slowly came to dom- pate heat to the surroundings. It does so by cir- inate. Since about six billion years ago (about a billion culating blood near the surface of the skin, by years before Earth formed), the expansion has, on exhaling warm, humidified air, and by evap- average, been accelerating. orating sweat. Nevertheless, the cosmic dance continues. Galax- These processes function best when am- ies that had been pulled together before the universe bient temperature is around 70 degrees began accelerating still have the chance to collide. Fahrenheit, where we feel most comfort- Collectively they form overdense patches of the uni- able, and they serve to maintain core body verse in which gravity still reigns. In our neighbor- temperature around 98 degrees F. But when hood the Andromeda galaxy, our largest companion, is actually the surroundings match core body temperature, the dispersal falling toward us, and we will have our first close encounter with mechanisms are not optimal, so we feel hot, especially when hu- it in just a few billion years’ time. midity is high. Humidity has a significant effect because water Our local group comprises Andromeda, the Magellanic on the body absorbs enormous amounts of heat and then dissi- Clouds and about 35 other galaxies, all of which lie in an even pates it by evaporation. Anything that interferes with this vapor- larger cluster called Virgo. Together we will travel through the ization of water (humid air, lack of a breeze, heavy clothing, and expanding universe, and we had better learn to like the compa- so on) makes us feel especially hot and uncomfortable. ■ ny—any galaxies that have not yet won the gravity war have Getty Images missed their chance. The universe is now split into pockets of in- have a question?... Send it to [email protected] or go to

teraction that will drift alone through the expanding cosmos. www.SciAm.com/asktheexperts CalCrary

SciAm6Ad_ol_20090116.indd 1 1/19/09 2:10:00 PM Reducing defects, boosting performance Helping to make better Makers of photovoltaic (PV) cells, the units that make up solar panels, were looking for ways to help them perform better—more efficiently... photovoltaic cells— to extract So, Hamamatsu began developing whole new systems to more precisely more power from the sun... identify problems and assess PV performance. One type of system uses very sensitive CCD Highly-sensitive infrared cameras to capture electro- detectors spot failure points luminescence from PV in this silicon PV module. cells or modules— to generate two-dimensional maps of their performance efficiency. Other Hamamatsu systems identify failure sites by capturing low-level light emissions from PV cells and superimposing those emission images

Hamamatsu is opening the new frontiers of Light

with microscopic images. Which precisely reveals defects, cracks, leaks and more. Still other systems employ high-sensitivity infrared detectors to analyze the temperature profiles of solar cells — to spot wiring shorts and other failure points that are indicated by temperature. The goal: a new genera-

Micro inspection of tion of higher-performance, electro-luminescence revealed this micro- higher-efficiency, longer-life scopic foreign material. solar panels, to better serve the need for green power around the globe. Solar power: it's one more industry in which Hamamatsu is applying its knowledge of light to help make our world a better place to live. http://jp.hamamatsu.com/en/rd/publication/

In the lower image above, a highly sensitive Hamamatsu CCD camera captures Photon is Our Business the electro-luminescence emitted from a polycrystalline photovoltaic module.