CONTENTS Volume 333 Issue 6046page 1095www.sciencemag.orgSCIENCEVOL 33326 AUGUST 20111061COVERFalse-colored backscattered electron image of a small rocky particle, 150 micrometers in size, recovered from the surface of near-Earth asteroid 25143 Itokawa by the Japanese spacecraft Hayabusa.Mineralogy and chemistry of the particle indicate that the asteroid consists of very primitive solar system material and has had a complex formation history. See the series of Reports beginning on page 1113.Image: Japanese Aerospace Exploration AgencyDEPARTMENTS1067This Week in Science1072Editors Choice1074Science Staff1108AAAS News & Notes1167New Products1168Science Careerspage 1084EDITORIAL1071Much More Than a TelescopeMichael S. TurnerNEWS OF THE WEEK1076 A roundup of the weeks top storiesNEWS & ANALYSIS1079 U.S. to Leave Consortium and Go It Alone After 20131080 Cambridge Seeks Global Reach, Says Univeristy Head1081Hayabusa Gets to the Bottom of Deceptive Asteroid Cloaking>> Report p. 11211083 8.7 Million: A New Estimate for All the Complex Species on EarthNEWS FOCUS 1084 Who Were the Denisovans? A Denisovan Legacy in the Immune System?>> Science Express Report by L. Abi-Rached et al.; Science Podcast1088Mending the Youngest Hearts1090 Europes Innovation Engine, Eager to Grow, Faces CriticismLETTERS1092 Endangered Wolves Fall Prey to PoliticsB. J. BergstromPredators Effects on Ecosystem EntropyW. T. FlueckLooking to NSF as an NIH ModelW. A. Yost 1093 TECHNICAL COMMENT ABSTRACTS1093 CORRECTIONS AND CLARIFICATIONSBOOKS ET AL.1094 The Changing BodyR. Floud et al., reviewed by L. Haddad1095Cricket RadioJ. Himmelman, reviewed by M. BerenbaumEDUCATION FORUM1096 Drawing to Learn in ScienceS. Ainsworth et al.>> Science PodcastPERSPECTIVES1098 Bringing Part of an Asteroid Back HomeA. N. Krot>> Reports pp. 1113, 1116, 1119, 1121, 1125, and 11281099Arranging a Cellular CheckerboardW. Choi and M. Peifer>> Report p. 11441100How Great Wings Can Look AlikeS. B. Carroll>> Report p. 11371102Another NOTCH for CancerR. H. Brakenhoff>> Reports pp. 1154 and 11571103A Window on the Sophistication of PlantsR. A. Jorgensen>> Report p. 11411104Architecturally Complex Polymers with Controlled HeterogeneityK. MatyjaszewskiSCIENCE PRIZE ESSAY1106 Astronomical Perspectives for Young ChildrenC. J. dman-Govender and D. KelleghanCONTENTS continued >>Published by AAASwww.sciencemag.orgSCIENCEVOL 33326 AUGUST 20111063CONTENTSpages 1099 & 1144pages 1102, 1154, & 1157page 1131REVIEW1109 Mitochondria and the AutophagyInammationCell Death Axis in Organismal AgingD. R. Green et al.REPORTS1113 Itokawa Dust Particles: A Direct Link Between S-Type Asteroids and Ordinary ChondritesT. Nakamura et al. >> Science Podcast1116 Oxygen Isotopic Compositions of Asteroidal Materials Returned from Itokawa by the Hayabusa MissionH. Yurimoto et al.1119 Neutron Activation Analysis of a Particle Returned from Asteroid ItokawaM. Ebihara et al.1121Incipient Space Weathering Observed on the Surface of Itokawa Dust ParticlesT. Noguchi et al.>> News story p. 10811125Three-Dimensional Structure of Hayabusa Samples: Origin and Evolution of Itokawa RegolithA. Tsuchiyama et al.1128Irradiation History of Itokawa Regolith Material Deduced from Noble Gases in the Hayabusa SamplesK. Nagao et al.Laboratory analysis of samples returned from an asteroid establishes a direct link between asteroids and meteorites and provides clues to the complex history of the asteroid and its surface.>> Perspective p. 10981131 Synthesis and Structure Determination of the Hierarchical Meso-Microporous Zeolite ITQ-43J. Jiang et al.A zeolite with microporous channels (6 to 7 angstrom diameter) and mesoporous channels (~2-nanometer diameter) was made.1134Unraveling the Perplexing Structure of the Zeolite SSZ-57C. Baerlocher et al.X-ray analysis reveals a zeolite structure in which 10-sided channels are periodically disrupted by 12-sided channels.1137 optix Drives the Repeated Convergent Evolution of Buttery Wing Pattern MimicryR. D. Reed et al.Heliconius buttery wing pattern mimicry is driven by cis-regulatory variation of the optix gene.>> Perspective p. 11001141Chaperonins Facilitate KNOTTED1 Cell-to-Cell Trafcking and Stem Cell FunctionX. M. Xu et al.Active transfer of a transcription factor between plant cells is required for stem cell maintenance.>> Perspective p. 11031144 Nectins Establish a Checkerboard-Like Cellular Pattern in the Auditory EpitheliumH. Togashi et al. Interactions between adhesion molecules support the checkerboard-like patterning of cells in the cochlea.>> Perspective p. 10991147Impacts of Fishing LowTrophic Level Species on Marine EcosystemsA. D. M. Smith et al. High harvest levels of lowtrophic level shes may have cascading marine ecosystem effects.1151 Expanding the Genetic Code of Escherichia coli with PhosphoserineH.-S. Park et al.Engineered bacterial translation can be used to direct site-specic insertion of an amino acid into proteins.1154 Exome Sequencing of Head and Neck Squamous Cell Carcinoma Reveals Inactivating Mutations in NOTCH1N. Agrawal et al.1157 The Mutational Landscape of Head and Neck Squamous Cell CarcinomaN. Stransky et al.The mutational prole of head and neck cancer is complex and may pose challenges to the development of targeted therapies.>> Perspective p. 11021161 MED23 Mutation Links Intellectual Disability to Dysregulation of Immediate Early Gene ExpressionS. Hashimoto et al.A single missense mutation is linked to intellectual impairment.CONTENTS continued >>Published by AAASwww.sciencemag.orgSCIENCEVOL 33326 AUGUST 20111065CONTENTSSCIENCEXPRESSwww.sciencexpress.orgPromoting the Peace Process by Changing Beliefs About Group MalleabilityE. Halperin et al.A belief that the beliefs of other groups are changeable rather than xed is conducive to negotiation.10.1126/science.1202925The Shaping of Modern Human Immune Systems by Multiregional Admixture with Archaic HumansL. Abi-Rached et al.Viral defense and embryo implantation mechanisms have been shaped by contributions from Neandertal and Denisovan genes.10.1126/science.1209202>> News story p. 1084MED12, the Mediator Complex Subunit 12 Gene, Is Mutated at High Frequency in Uterine LeiomyomasN. Mkinen et al.Uterine broids frequently harbor mutations in a specic gene that has been implicated in transcriptional regulation.10.1126/science.1208930Transformation of a Star into a Planet in a Millisecond Pulsar BinaryM. Bailes et al.Timing observations of a millisecond pulsar reveal a planet that is far denser than any known planet. 10.1126/science.1208890A Reservoir of Ionized Gas in the Galactic Halo to Sustain Star Formation in the Milky WayN. Lehner and J. C. HowkClouds of ionized gas located inside our galaxy provide a major supply of matter for fueling ongoing star formation.10.1126/science.1209069TECHNICALCOMMENTSComment on Drought-Induced Reduction in Global Terrestrial Net Primary Production from 2000 Through 2009A. Samanta et al.Full text at www.sciencemag.org/cgi/content/full/333/6046/1093-cComment on Drought-Induced Reduction in Global Terrestrial Net Primary Production from 2000 Through 2009B. E. MedlynFull text at www.sciencemag.org/cgi/content/full/333/6046/1093-dResponse to Comments on Drought-Induced Reduction in Global Terrestrial Net Primary Production from 2000 Through 2009M. Zhao and S. W. RunningFull text at www.sciencemag.org/cgi/content/full/333/6046/1093-eSCIENCEONLINESCIENCE(ISSN0036-8075)ispublishedweeklyonFriday,exceptthelast weekinDecember,bytheAmericanAssociationfortheAdvancementof Science, 1200 New York Avenue, NW, Washington, DC 20005. Periodicals Mail postage(publicationNo.484460)paidatWashington,DC,andadditionalmailing ofces.Copyright2011bytheAmericanAssociationfortheAdvancementof Science. The title SCIENCE is a registered trademark of the AAAS. Domestic individual membershipandsubscription(51issues):$149($74allocatedtosubscription). Domestic institutional subscription (51 issues): $990; Foreign postage extra: Mexico, Caribbean(surfacemail)$55;othercountries(airassistdelivery)$85.Firstclass, airmail,student,andemeritusratesonrequest.CanadianrateswithGSTavailable uponrequest,GST#125488122.PublicationsMailAgreementNumber1069624. Printed in the U.S.A. Change of address: Allow 4 weeks, giving old and new addresses and 8-digit account number. Postmaster: Send change of address to AAAS, P.O. Box 96178, Washington, DC 200906178. Single-copy sales: $10.00 current issue, $15.00 back issue prepaid includessurfacepostage;bulkratesonrequest.Authorizationtophotocopy materialforinternalorpersonaluseundercircumstancesnotfallingwithinthefair useprovisionsoftheCopyrightActisgrantedbyAAAStolibrariesandotherusers registered with the Copyright Clearance Center (CCC) Transactional Reporting Service, provided that $25.00 per article is paid directly to CCC, 222 Rosewood Drive, Danvers, MA 01923. The identication code for Science is 0036-8075. Science is indexed in the Readers Guide to Periodical Literature and in several specialized indexes.SCIENCENOWwww.sciencenow.orgHighlights From Our Daily News Coverage Eco-Friendly Chilean Sea Bass May Not Be So GreenA genetic study nds the rst evidence of mislabeling in sh certied as sustainable.http://scim.ag/ecoseabassImmune System Protects Female Bedbugs From Traumatic SexInsects anticipate infections from violent male insemination.http://scim.ag/bedbugbacteriaLager Beers Mystery Yeast Scientists identify a microbe that is key to the brewing process. http://scim.ag/lageryeastSCIENCESIGNALING www.sciencesignaling.orgThe Signal Transduction Knowledge Environment23 August issue: http://scim.ag/ss082311RESEARCH ARTICLE: Tumor Progression Locus 2 Mediates Signal-Induced Increases in Cytoplasmic Calcium and Cell MigrationM. Hatziapostolou et al.The kinase Tpl2 triggers calcium signaling and cell migration downstream of various receptors implicated in cancer and inammation.PERSPECTIVE: TBK1 Mediates Crosstalk Between the Innate Immune Response and AutophagyH. Weidberg and Z. ElazarPhosphorylation of an autophagy adaptor by a kinase involved in innate immune responses limits pathogenic bacterial growth.PODCASTH. D. Mansvelder and A. M. VanHook2 subunitcontaining nicotinic acetylcholine receptors in the prefrontal cortex are sufcient for acetylcholine-mediated enhancement of attentional focus.SCIENCECAREERSwww.sciencecareers.org/career_magazineFree Career Resources for Scientists Experimental Error: This Is Only a TestA. RubinAs we are training to become fully edged scientists, we ourselves are the test subjects.http://scim.ag/EE_TestingCreating Your Own Job: From Engineer to EntrepreneurS. A. HolgateA layoff set engineer Diana Hodgins on a new career path, leading eventually to managing her own company. http://scim.ag/Diana_HodginsIn Person: A Sabbatical in NamibiaL. A. Levin and D. M. CheckleyOn the heels of our feature on doing science in Namibia, two scientists describe their sabbatical experiences there.http://scim.ag/Namibia_SabbaticalSCIENCETRANSLATIONAL MEDICINEwww.sciencetranslationalmedicine.orgIntegrating Medicine and Science24 August issue: http://scim.ag/stm082411COMMENTARY: Herding CATSG. A. PetskoThe National Center for Advancing Translational Sciences seems primed to polarize scientists while possibly failing to drive biomedical research and development forward. RESEARCH ARTICLE: Long-Term Persistence of a Polyclonal T Cell Repertoire After Gene Therapy for X-Linked Severe Combined ImmunodeciencyH. B. Gaspar et al. RESEARCH ARTICLE: Hematopoietic Stem Cell Gene Therapy for Adenosine DeaminaseDecient Severe Combined Immunodeciency Leads to Long-Term Immunological Recovery and Metabolic CorrectionH. B. Gaspar et al.PERSPECTIVE: A Tale of Two SCIDSK. L. Shaw and D. B. KohnGene therapy can restore immune and metabolic function in immunodecient patients.RESEARCH ARTICLE: Potent Kinetic Stabilizers That Prevent Transthyretin-Mediated Cardiomyocyte ProteotoxicityM. M. Alhamadsheh et al.A screen for transthyretin ligands that inhibit protein aggregation identies agents that prevent amyloid toxicity in cardiomyocytes.SCIENCEPODCASTwww.sciencemag.org/multimedia/podcastFree Weekly Show On the 26 August Science Podcast: dust particles from asteroid Itokawa, new insights into the Denisovans, drawing to learn in science, and more.SCIENCEINSIDERnews.sciencemag.org/scienceinsiderScience Policy News and AnalysisPublished by AAAS1067CREDITS (TOP TO BOTTOM): ARNAUD MARTIN; BAERLOCHER ET AL.Continued on page 1069www.sciencemag.orgSCIENCEVOL 33326 AUGUST 2011Mature Mitochondria? Mitochondria are the essential source of meta-bolic energy for the cell. These organelles direct crossroads from which cells can move down a path that leads to cell death or to inammatory damage to an organism. They are thus important factors of certain diseases and, more universally, of the aging process. Green et al. (p. 1109) review recent insights into mitochondrial func-tion, their roles in the control of cell death and in chronic inammation, and the role of autophagy or, more specically, mitophagy in protecting cells from mitochondrial damage.Extraterrestrial Dust Collection The Japanese Hayabusa spacecraft returned to Earth on 13 June 2010 carrying within it a pre-cious but invisible cargo1534 particles of dust from the surface of the asteroid Itokawa, which the spacecraft visited in 2005. These particles, up to 180 micrometers in size, are the rst material ever fetched from an asteroid and returned to Earth for laboratory analysis (see the Perspec-tive by Krot; see the cover). Nakamura et al. (p. 1113) describe the mineralogy of the particles; Yurimoto et al. (p. 1116) report measurements of the oxygen isotopic composition of minerals in 28 dust grains; and Ebihara et al. (p. 1119) discuss trace-element data for one of the largest grains in the collection. These studies conrm that the material is indeed extraterrestrial in origin and is similar to material in stony meteorites of the LL type, thus establishing an unequivocal link between asteroids and meteorites. Previously, meteorites were thought to originate from asteroids, based on spectroscopic studies of aster-oid surfaces. However, these surfaces suffer from the effects of space weathering, which modies their spectral properties compared with those of meteorites. Noguchi et al. (p. 1121) show that 5 of the 10 particles analyzed show evidence of surface alteration related to their exposure to the space environment on the surface of Itokawa and conclude that the process is different from the one operating on the Moons surface. The particles col-lected by Hayabusa sample the asteroids regolith, the layer of unconsolidated material that covers rocky surfaces. Based on the texture and shapes of the particles and on noble gas analyses of three grains, Tsuchiyama et al. (p. 1125) and Nagao et al. (p. 1128) trace the history of Itokawas regolith, the second extraterrestrial regolith to have been sampled after the Moons. Zeolites Up CloseIn the preparation of microporous zeolitic materials for catalysis, the introduction of hier-archical porosity has been of great interest. Because pores have multiple-size scales, it should be possible to enhance catalytic activ-ity by controlling dif fusion characteristics. Jiang et al. (p. 1131) developed a zeolitic topology in which this hierarchical porosity is a natural feature of the material through the use of organic and inorganic structure-directing agents. Zeolites vary widely in the size and arrangement of their pore structures, but their lattice geometries can generally be described by a relatively simple replicated core arrangement. Baerlocher et al. (p. 1134) used sophisticated analysis of x-ray diffraction data to uncover the structure of an unexpectedly complex zeolite variant, in which the unit cell comprises 99 silicon atoms (compared with ~20 or fewer observed in conventional zeolites). Getting There Is Only Half the Fun Although most transcription factors are syn-thesized in the same cell in which they act, in plants some transcription factors get shipped into other cells, where they take action on the genes of the destination cell. The transcrip-tion factors KNOTTED1 (KN1) of maize and the closely similar SHOOTMERISTEMLESS (STM) of Arabidopsis, as well as SHORTROOT (SHR) of Arabidopsis, are a few of these peripatetic regulators. These factors need to travel through the plasmodesmata that connect one cell to another. Xu et al. (p. 1141; see the Perspective by Jorgensen) used a reporter system in Arabidopsis that depends on the transport of the transcription factor to direct trichome development. A spe-cic chaperonin complex was required in the recipient cell for full function of KN1 or STM, which highlights the need for refolding of these transcription factors after transport.Playing CheckersDevelopmental patterning is very important in the arrangements of cells within organs and tis-sues. The organ of Corti in the inner ear contains >FINDINGS Helping Fat Mice Live LongerThey work in micebut will they work in people? Thats one question hanging over a class of compounds intended to boost SIRT1, a protein thought to mimic the effects of calorie restriction. In a host of animals, slashing calories extends life and preserves healthand a study in Scientic Reports published 18 August shows that a particular SIRT1 booster helps obese mice live longer. The drug cut the amount of fat in the animals livers and made them more responsive to insulin. It also prolonged their lives by 44% compared with control micebut the obese animals still died earlier than normal mice. Closely related compounds are currently in clinical trials in people.The new study is at odds with an earlier study by a group at Pzer, which reported that this compound and others like it dont activate the SIRT1 protein, and that they have many unintended targets in the body, suggest-ing theyre unlikely to make good drugs. Disease-Fighting Mosquitoes Proliferate in Field TestA mosquito strain specially created to ght dengue, a viral disease that causes head-aches, rash, and excruciating muscle and joint pains, has shown promise in its rst open eld study in two small towns in northern Australia.The experimental mosquitoesa spe-cies called Aedes aegypti, which is dengues main vectorare infected with a strain of Wolbachia pipientis, an intracellular bacte-rium that makes the insects virtually unable to transmit dengue but also has a way of spreading rapidly through their populations by playing strange tricks with their sex lives (Science, 10 December 2010, p. 1460). Led by Scott ONeill from Monash University in Melbourne, the team released between 10,000 and 20,000 infected mosquitoes NEWS OF THE WEEKweekly in each of the towns for 10 weeks. Six weeks after the nal release, the entire population in both towns had become infected, the team reported 25 August in Nature.The study wasnt designed to have an effect on dengue, which is rare in Aus-tralia. Field tests in Vietnam, Indonesia, Thailand, and Brazil, all endemic coun-tries, are awaiting approval; ONeill says the rst released could happen within a year. http://scim.ag/_DengueIberian Lynx Not Jinxed by GeneticsA study of ancient DNA has given scientists more hope that the worlds most endangered cat species can be sal-vaged. Habitat destruction and the decline of its main prey, the European rabbit, have caused the population of the Iberian lynx (Lynx pardinus) to plummet below 300 individuals in two isolated areas in Spain. Scientists are trying to help with a breeding program, but some believe a lack of genetic diversitywhich leads to inbreeding problems and an inability to adapt to changemay doom the species. But a new study of DNA found in fossil bones shows that the Iberian lynx has had very low genetic diver-sity, and presumably small populations, for at least 50,000 years. For reasons that are unclear, it always got by, the research-ers conclude in their paper in Molecular Ecology. If the lynx is lost, they say, dont blame its genes; blame the lack of political will to save it.Published by AAAS on August 25, 2011www.sciencemag.orgDownloaded from www.sciencemag.orgSCIENCEVOL 33326 AUGUST 2011 1077NEWSCREDITS (TOP TO BOTTOM): BECKY KAGAN/ADVANCED IMAGING AND VISUALIZATION LABORATORY, WOODS HOLE OCEANOGRAPHIC INSTITUTION; POLYTECHNIC UNIVERSITY OF TURIN; DAVID WACEY/UNIVERSITY OF WESTERN AUSTRALIAWitnessing a Watery JunkyardDuring World War II, German U-boats sank dozens of U.S. ships off the coast of North Carolina, creating a watery junkyard known as the Graveyard of the Atlantic. Those ships are now the target of scientists from Woods Hole Oceanographic Institution (WHOI), who are using a remotely operated vehicle outtted with underwater 3D cameras to capture images of sunken ships previously located with side-scan sonar. In mid-August, Evan Kovacs, director of 3D photography for WHOIs Advanced Imag-ing and Visualization Lab, and his team took new 3D and 2D images of the ships (shown here), as part of an ongoing project with the National Oceanic and Atmospheric Admin-istration and the National Park Service to study their deterioration and impact on the environment. Video and imagery have always been key for marine archaeology, Kovacs says, but before 3D, its [been] difcult to pull hard, quantitative data out of it. The 3D data, he says, allow scientists to analyze rates of collapse and corrosion. And, he adds, 3D images are a great outreach tool: Its an insanely immersive environment.THEY SAID ITTo be clear. I believe in evo-lution and trust scientists on global warming. Call me crazy. Tweet by 2012 Republican presidential candidate Jon Huntsman on 18 August after Texas governor and Republican candidate Rick Perry said that evolution is a theory thats out there and questioned whether climate scientists manipulated data for money.FINDINGSNEWSMAKERWashington, D.C.5New U.S. Conict of Interest RulesThe U.S. government this week issued new rules aimed at cracking down on nancial conicts of interest in biomedical research. The update of a 16-year-old regulation will require researchers funded by the Pub-lic Health Service to report more of their income from drug companies and other out-side sources to their institutions. The regula-tions also require that institutions, rather than investigators, determine if any payments con-stitute a conict. http://scim.ag/_CoI Reformer Takes Reins in RomeThe Italian National Research Council (CNR)a 1 billion basic research agency with 100 institutes around the countrymay be headed for some major changes with the appointment on 13 August of Francesco Profumo, the successful, reform-minded rec-tor of the Polytechnic University of Turin, Fossil Cells Are Worlds OldestScientists say they have discovered 3.4-bil-lion-year-old cells, possibly the oldest fossils ever found. Geologists Martin Brasier of the University of Oxford in the United Kingdom and David Wacey of the University of West-ern Australia in Crawley discovered the fossil cells between cemented sand grains from an ancient beach in Western Australia. The fossil cells were hollow, and some were clustered together in groups sur-rounded by what looked like a membrane. The morphology is very cell-like, Brasier says. The cells were also patchily distrib-uted in the sediment, just as modern bacteria tend to congregate near sources of food, the researchers reported online 21 August in Nature Geoscience.Old cells. Ancient life (inset) found in Australia.as CNRs new president. Italian scientists say he is likely to modernize and revitalize the agency, which has been plagued by budget cuts.While at the Polytech-nic University, Profumo, 58, worked hard to build international ties, turn scien-tic research into economic development and innova-tion, and forge tight collaborations with industry. Profumo says hell try some of the same recipes at CNR and will spur Italy to get more research money from the European Union. Italy currently contributes 14% of the E.U.s research funds but receives only 9% of the grants the union distributes.Profumo has proved his exceptional skills in coordinating research, technology, and industry, and he will give CNR a central role in applied research, says Luigi Donato, founder and former head of the CNR Insti-tute of Clinical Physiology in Pisa. The latter aspect is crucial in this moment of nancial crisis. http://scim.ag/_ProfumoThe two scientists say their chemical anal-yses of the minerals near the cells suggest the microorganisms depended on sulfur for fuel. Such a beach might have been lifes rst breeding ground, Brasier says. The work represents some of the best evidence for the nature of Earths earliest life, says Bruce Runnegar, a geologist at the University of California, Los Angeles, who was not involved in the study. http://scim.ag/fossilcellsPublished by AAAS on August 25, 2011www.sciencemag.orgDownloaded from 1078 26 AUGUST 2011VOL 333SCIENCEwww.sciencemag.org CREDITS (TOP TO BOTTOM): (PHOTOILLUSTRATION IMAGES) ISTOCKPHOTO.COM; ARS/USDA; FOTOSEARCH8.7 million +/-1.3 million Number of eukaryote species on Earth, including 6.5 million on land and 2.2 million in the oceans, according to a report by Census of Marine Life scientists in PLoS Biology.239 millionCost of unused H1N1 vaccines in Germany that are expired and being destroyed. Three-quarters of 34 million doses ordered went unused due to distribution problems and confusion over how many doses conferred protection.Random SampleA(nother) Modest ProposalLions roaming the streets of Athens, gorillas swinging from trafc lights in Spainsure, it might be dangerous, but think of the ecotourism dollars! That revenue could provide a badly needed boost to troubled nations econo-mies, says the (so-called) Coalition of Financially Challenged Countries With Lots of Trees (CoFCCLoT). In their Modest Proposal, published in Biotropica on 16 August, CoFCCLoT also suggests that wealthy Western nations reforest their land, which would help slow climate change and provide new habitat for displaced and endangered species such as bears and wolves. Such a proposal may sound unreasonable, but it is the kind of environmentally conscious action that the West expects of countries that harbor tropical forest, says conservation scien-tists Erik Meijaard and Douglas Sheil, who created the ctitious coalition. Conservationists in wealthy countries shouldnt complain about tropical deforestation, but then drink a cup of Brazilian coffee every morning and buy cheap palm oil, the authors say. Meijaard and Sheil hope to use satire to highlight such double standards. What were trying to show is the viewpoints that people are having are very often black and white. If you want to make political progress its a natural give and take, Meijaard says. They modeled their paper on Jonathan Swifts A Modest Proposal, which suggested an ironic solution to poverty and population growth in 18th century Ireland: Eat the children. Humor can reveal us as holding dual standardsas most of us do, Sheil says. Once you can laugh at your own viewpoint its easier to step outside [it] and see how narrow-minded youve been. >>FINDINGS Helping Fat Mice Live LongerThey work in micebut will they work in people? Thats one question hanging over a class of compounds intended to boost SIRT1, a protein thought to mimic the effects of calorie restriction. In a host of animals, slashing calories extends life and preserves healthand a study in Scientic Reports published 18 August shows that a particular SIRT1 booster helps obese mice live longer. The drug cut the amount of fat in the animals livers and made them more responsive to insulin. It also prolonged their lives by 44% compared with control micebut the obese animals still died earlier than normal mice. Closely related compounds are currently in clinical trials in people.The new study is at odds with an earlier study by a group at Pzer, which reported that this compound and others like it dont activate the SIRT1 protein, and that they have many unintended targets in the body, suggest-ing theyre unlikely to make good drugs. Disease-Fighting Mosquitoes Proliferate in Field TestA mosquito strain specially created to ght dengue, a viral disease that causes head-aches, rash, and excruciating muscle and joint pains, has shown promise in its rst open eld study in two small towns in northern Australia.The experimental mosquitoesa spe-cies called Aedes aegypti, which is dengues main vectorare infected with a strain of Wolbachia pipientis, an intracellular bacte-rium that makes the insects virtually unable to transmit dengue but also has a way of spreading rapidly through their populations by playing strange tricks with their sex lives (Science, 10 December 2010, p. 1460). Led by Scott ONeill from Monash University in Melbourne, the team released between 10,000 and 20,000 infected mosquitoes NEWS OF THE WEEKweekly in each of the towns for 10 weeks. Six weeks after the nal release, the entire population in both towns had become infected, the team reported 25 August in Nature.The study wasnt designed to have an effect on dengue, which is rare in Aus-tralia. Field tests in Vietnam, Indonesia, Thailand, and Brazil, all endemic coun-tries, are awaiting approval; ONeill says the rst released could happen within a year. http://scim.ag/_DengueIberian Lynx Not Jinxed by GeneticsA study of ancient DNA has given scientists more hope that the worlds most endangered cat species can be sal-vaged. Habitat destruction and the decline of its main prey, the European rabbit, have caused the population of the Iberian lynx (Lynx pardinus) to plummet below 300 individuals in two isolated areas in Spain. Scientists are trying to help with a breeding program, but some believe a lack of genetic diversitywhich leads to inbreeding problems and an inability to adapt to changemay doom the species. But a new study of DNA found in fossil bones shows that the Iberian lynx has had very low genetic diver-sity, and presumably small populations, for at least 50,000 years. For reasons that are unclear, it always got by, the research-ers conclude in their paper in Molecular Ecology. If the lynx is lost, they say, dont blame its genes; blame the lack of political will to save it.Published by AAAS on August 25, 2011www.sciencemag.orgDownloaded from NEWS & ANALYSISwww.sciencemag.orgSCIENCEVOL 33326 AUGUST 20111079NEWS & ANALYSISCREDITS (TOP TO BOTTOM): NEWSCOM; IODP/JAMSTECPleading poverty, the U.S. National Science Foundation (NSF) is ending a decade-long era of international collaboration in ocean drilling, leaving Japan and Europe to fend for themselves.Last week, NSF ofcials quietly posted a notice to the community that the United States would be pulling out of the Integrated OceanDrillingProgram(IODP)whenthe program expires in September 2013. Instead ofrenewingtheIODPrelationship,which involves three drill ships and 26 countries, the United States hopes to reduce costs by going it alone and attracting enough foreign contributions to return its own drill ship to full-time operation. Given the likely budget outlook, says Timothy Killeen, NSF assis-tant director for geosciences, this is the best way to support U.S. investigators.The proposed realignment harkens back to an earlier era of scientic ocean drilling. Between 1985 and 2003, the United States led the Ocean Drilling Program that oper-ated the JOIDES Resolution, also known as the JR (Science, 24 October 2008, p. 512). Othercountriescontributed40%ofthe funding in return for the opportunity to par-ticipate. Since 2003, IODP, co-led by Japan and the United States, has used a refurbished JOIDES Resolution along with the newer, larger,andfarmorecapableChikyubuilt and operated by Japan (Science, 22 Febru-ary 2008, p. 1037). On occasion a European consortium has provided special platforms, such as one leased for drilling in ice-choked Arctic waters.TheChikyuallowsscientiststodrill deeper into the sea oors most challeng-ingtargets,suchasthefaultthatgener-ates great earthquakes off of Japan. But it is much more expensive to operate than the JR. Indeed, all manner of higher costsfor fuel, drilling pipe, and unexpected repairshave been a perennial problem for the drill-ingplatforms. Asaconsequence,Chikyu has spent only 3 to 4 months a year doing scientic drilling, with some of the balance of its time hired out to industry for oil and gas exploration.A budget squeeze has also forced NSF to trim 2 months off the JRs scientic sched-ule in 2012, to only 6 months of operation. A 28 June update from NSFs Division of OceanSciencesDirectorDavidConover notes that operating costs for the JR have also skyrocketed, and that NSF is still pay-ingforcostoverrunsfromtheJRrefur-bishment, completed in early 2009. Some $25 million in one-time funding for IODP from the 2009 stimulus package is almost exhausted,andNSFsoverallbudgetthis year is 1% lower than in 2010, when it spent $63 million on IODP.In their letter, NSFs Killeen and Conover announceanewoperatingmodelthat streamlinesoperatingcostsandgenerates new external sources of revenue to support the JR. While short on details, the proposed realignment would have NSF operate the JR independently of any other lead agency, but the agency would solicit direct contributions from other countries. All told, we believe this will get the JR close to if not at full-duty operation, Killeen says.U.S.scientistswhohavebuilttheir careers on rock and mud retrieved by ocean drillingsayNSFsdecisiontogoitalone makes sense given its gloomy nancial out-look. I view the proposal as an encourag-ing sign, says geochemist Steven DHondt oftheUniversityofRhodeIsland,Narra-gansett. What were hearing is that NSF is going to protect the capability we provide to the international community. To Theodore Moore Jr., a professor emeritus at the Uni-versity of Michigan, Ann Arbor, the options were either dissolve the partnership and go our separate ways or kill everything. Theres lots of good science that remains to be done that is within the JRs capabilities.Japanese ofcials say that they arent sur-prised by NSFs decision to pull out but that the timing is unfortunate. I expected some-thinglikethiswasgoingtohappen,says Asahiko Taira, an executive director of the Japan Agency for Marine-Earth Science and Technology. Both sides have long been frus-trated with a rigid structure set up 15 years ago when the research environment was quite different, he says. Since then, budgets have shrunk. There is also growing public scrutiny of scientic efforts and increasing expecta-tions that research be more relevant to social needs.Itdidnthelp, Tairasays,thatNSF ocean drilling program ofcials had a dif-cult time communicating with the career civil servants at Japans Ministry of Educa-tion (MEXT).Still, the decision comes just weeks after theconsortiumunveiledanew10-year planforscientificexplorationthatwould havereliedupondrillingplatformsfrom the United States, Japan, and Europe. The NSF announcement was completely at odds with the discussions among the participat-ing countries, says Shingo Shibata, director of deep-sea research for MEXT. Taira says Japan will continue ocean drilling and will look to the international community not so much for funding but for scientic proposals and scientic participation. He would still like to see an overarching science advisory structure to maintain an international vision for ocean drilling and to avoid duplication.Although Shibata says that we understand NSFs decision given its severe nancial situa-tion, Taira worries that the U.S. is becoming more inward-looking because of budget con-straints. Such an attitude, he says, would be a blow to global scientic cooperation.RICHARD A. KERR AND DENNIS NORMILEU.S. to Leave Consortium And Go It Alone After 2013SCI ENTI FI COCEANDRI LLI NGSailing away. The U.S. JOIDES Resolution (top) and Japans Chikyu are parting company.Published by AAAS on August 25, 2011www.sciencemag.orgDownloaded from 26 AUGUST 2011VOL 333SCIENCEwww.sciencemag.org1080NEWS&ANALYSISCREDIT: UNIVERSITY OF CAMBRIDGEAfter3yearsinchargeoftheMedical ResearchCouncil,theprimarygovern-mentfunderofbiomedicalresearchinthe United Kingdom, Leszek Borysiewicz, who is universally known as Borys, switched backtotheacademylastOctober.He joined the University of Cambridge as vice-chancellor, the ancient universitys top admin-istrative position. Just after he got there, the ConservativeLiberalDemocratcoalition government announced unexpectedly that a cap on annual student tuition fees would rise from3000to9000(about$15,000)per annum. At the same time, most public support for university teaching will be withdrawn in England (other parts of the United Kingdom haveautonomyinthissphereandwillnot follow suit). The change has rocked the U.K. university system and even prompted student riots, but is now being swiftly implementedalongside a freeze in research funding.An immunologist who made his scien-tic reputation developing a vaccine for cer-vical cancer, Borysiewicz early in his career had a brief spell lecturing at CambridgeoftenratedasEuropesleadingresearch universitybutwaseducatedattheUni-versity of Wales in Cardiff and earned his administrativestripesasdeputyrectorof Imperial College London. With his impos-ing presence, amiable manner, and Polish-tinged Welsh accentboth his parents were refugees from Poland, and he spoke no Eng-lish until the age of 5Borysiewicz stands outsharplyfromtheOxbridge-educated men who still dominate the British estab-lishment. As his rst academic year in the position drew to a close, the vice-chancellor sat down with Science in his ofce in the Old Schools building for a frank discussion of the future of Cambridge and other U.K. uni-versities. This interview has been edited for brevity and clarity; an extended version can be found online at http://scim.ag/Borys. COLIN MACILWAINColin Macilwain is a writer in Edinburgh, U.K.Q: Radical changes in funding for univer-sity teaching are being implemented in the United Kingdom, and it has been argued thattheuniversitiesresponsehasbeen supine. Why have they been unable to rally support behind public funding of univer-sity teaching?L.B.: The whole sector is 137 independent institutions, and they each have to look at their own positions. Cambridge came to a unanimous view; it didnt hit the headlines, but it was a rm statement of the universi-tys position. In essence, it said that we do not agree with reduction of state support for teaching, we will continue to take in under-graduate students with the same approach to selection as before, and that we believe in the autonomy of institutions and not setting external quotas [on student numbers]. Those were very rm statements that represent the position of the university.Q: If Britains universities are as good as they say they are, and fundamental to U.K. business and society, why is the country, as some would argue, going to hell?L.B.: I could suggest three reasons: Universi-ties work in the medium- and long-term, they dont do quick xes. Secondly, top universi-ties focus on major problems that are difcult to solve; again, these are long-term problems with no quick xes. And thirdly, while uni-versities are repositories of knowledge, and it is important that these repositories are turned to the public good, we know that this transla-tion takes time. The Medical Research Coun-cils report on biomedical science, Medical Research: Whatsit Worth?,estimatedthe translation time at 17 years.Q:IsnttheGermanuniversitysystem, with its emphasis on breadthrather than excellence at the very topand vocational education, proving to be more strategically effective?L.B.: In certain sectors, Germany is in the lead. In others, particularly life sciences and biomedicine, it is not. That may depend on particular skills in the university system. Q:Howareyoucuttingyourclothin response to the research funding outlook?L.B.: If we just look at the revenue funding from the research councils, they are looking to make some reductions. Well be trying to attract as much of the pot as we can from them, and we will continue to diversify our research base. We believe that strategy will work appro-priately for Cambridge. But the capital budget is a very real problem. Were going to see a reduction in capital budget coming through SIF[theHigherEducationFundingCoun-cil for Englands Strategic Investment Fund] from 33 million to 11 million per annum. There are also cutbacks in equipment budgets. For Cambridge, maintaining the best pos-sibleinfrastructureisabsolutelyvital,so that our academics can compete and interact with industry, which is at the cutting edge. If we fall below that, it is going to be a core weakness.Isuspectwhatthegovernment may be thinking is that a couple of years isnt goingtomakemuchdifferencebutany sustained reduction in capital investment in universities can do damage in the long term, particularly to the most internationally com-petitive parts of our university system. Q: What are your research priorities?L.B.: Cambridge is going to maintain a very broad research direction, for two reasons. Weattractacademicsbyprovidingthem with time and space and opportunity to fol-low their own instincts; and I also believe thatmajorparadigmshiftsinthinking,in thehumanitiesorinsciences,canactu-ally occur. But this is going to be difcult, because funders have more and more dif-culty sustaining the investigator-led pro-grams, which support this kind of science. Theyareinsteadmovingtowardsgrand challenges, and Cambridge is going to have to respond to that. This year, weve identied strategic priorities to help us compete for large-scale funding in areas such as energy, cancer,infectiousdisease,neuroscience, and linguistics. In these areas, were going Cambridge Seeks Global Reach, Says University HeadNEWSMAKERI NTERVI EW: LESZEKBORYSI EWI CZBack to school. Borysiewicz has returned to uni-versity administration at a challenging time for the United Kingdoms higher education sector.Published by AAAS on August 25, 2011www.sciencemag.orgDownloaded from www.sciencemag.orgSCIENCEVOL 33326 AUGUST 20111081NEWS&ANALYSISCREDITS (TOP TO BOTTOM): T. NOGUCHI ET AL., SCIENCE 333, 6046 (26 AUGUST 2011); COURTESY OF JAXA Astronomers had a problem. They knew that meteorites start out as parts of bigger rocks in space, mostly asteroids. But when they com-paredthespectralcolorsofasteroidswith those of the most common kind of meteorite that falls to Earth, they couldnt nd a match. NowJapaneseresearchershavefoundthe answer in the rst bits of asteroid returned to Earth by a spacecraft. Dissecting the samples, they have nailed the source of Earths most common meteorites and gotten to the root of astronomers color problem. The blast of the solar wind and perhaps other space weath-ering processes, it turns out, alteredthespectralcolorof themostcommontypeof asteroidsintheinneraster-oid beltthe S typesand masked their true nature.Mostplanetaryscien-tists,afterclose-upbutstill nothands-oninspectionof asteroids,hadconcluded that exposure to the rigors of spacemustalterthesurface ofS-typeasteroidsbutthe hard proof still wasnt there. Then, in June 2010, Japans Hayabusa space-craft returned a sample of the S-type asteroid Itokawa. In March at the Lunar and Plane-tary Science Conference (Science, 15 April, p. 302), Japanese researchers presented their elemental, isotopic, and mineralogical anal-ysesof50Itokawaparticlessmallerthan 100micrometers.Theyreportthoseand additional analyses in detail in this issue of Science (pp. 1113-1130).ThematchbetweenItokawaandthe mostcommontypeofmeteoriteonEarth, the ordinary chondrites, is right on, just as astronomerspredicted. Thatresultbrings an irrefutable closure to the long-standing S asteroid conundrum, says asteroid spe-cialistClarkChapmanoftheSouthwest Research Institute in Boulder, Colorado.Remotesensing,however,couldnt revealwhatcreatedthedeceptivealtera-tion. For that, Hayabusa analysts used scan-ningtransmissionelectronmicroscopy (STEM) to examine vanishingly thin slices of 10 Itokawa rock particles that averaged 52micrometersindiameter.Theywere lookingfornanoblobsthatareopaque and about the same size as the wavelength of light so they could scatter light and make Itokawa look redder, at least to the supersen-sitive eye of a spectrometer. That sort of red-dening is what misled the astronomers.Ontherimsoffiveoftheparticles, TakaakiNoguchiofIbarakiUniversityin Japan and 17 colleagues found two thin lay-ers. The outer, surface layer was only 5 to 15nanometersthickandcontained1-to 2-nanometer-wide blobs of iron sulde. To judge by the STEM images, the outer layer and its iron-sulde nanoblobs formed when micrometeorite impacts, solar wind, or both vaporizednearbymineralsandthevapor condensedontothe rock particle.I mme d i a t e l y beneaththeouter layerofiron-rich Itokawaparticles wasanotherlayer, 20 to 50 nano meters thick,containing only metallic iron nanoblobs. These blobs must have been formed by solar wind when charged particles such as protons penetrated Itokawa rock particles. Unless the outer lay-ersiron-sulfidenanoblobshaveanunex-pectedlylargeeffectonlight,thesemore abundant metallic iron nanoblobs created by solar wind may be the major cause of the spectralmodificationofItokawa,writes Noguchi in an e-mail. So S-type asteroids seem to have gotten a sunburn from sitting too long in the wind of deep space. Their skin was so reddened that for decades the parents of terrestrial meteorites went unrecognized.RICHARD A. KERRHayabusa Gets to the Bottom of Deceptive Asteroid CloakingPLANETARYSCI ENCEto make sure we have the interdisciplinarity to make us competitive. Q: TheEuropeanResearchCouncilhasa good reputation, but the quality of other European Commission research programs has been criticized. Is it improving?L.B.:ThereareissuesthatIwouldhave with some of the directions Europe is tak-ing: for example, how on Earth the priori-ties for the European Institute of Technology are being set without seemingly any consul-tationwiththeacademiccommunity(see p. 1090). But engagement with Europe, both with the commission and through bipartite arrangements with universities in Europe, is a very important way forward. Were among the lead universities in Europe, and I think we should take on that leadership role and extend it into Europe to work hand-in-glove with partners in Germany and France and other European countries. Q: Whats your strategy for Asia? Will you open campuses there?L.B.: Weve tied our research strategy and our international strategy together. We do not see that that strategy is going to involve awholesaleexpansionofundergraduate education, nor do we see extra undergrad-uate campuses as being necessary. But our efforts in research are going to be far more inter national; they are going to be focused on direct interactions with the Far East, just as much as with North America and Europe. Q:Willyoulookatremoteresearch campuses?L.B.: Yes, we willwhen we have a critical massofinvestigator-ledresearchthathas reachedapointwhereinstitutional-level support is appropriate. We are now identi-fying areas where we should move towards institution-levelinteraction.Ivebeento China twice and Singapore twice this year, once to India in spring and Im going back again in September, to look at where such opportunitiesexist.Ibelievetopinterna-tional universities will gradually be working together. They can make a dent into these global problems, but it will be done on the basis of international cooperation. Were not going to nd solutions to global warming instantaneously.Q: Havent previous attempts to build inter-national partnerships between universities tended to zzle?L.B.: Historically what you say may be cor-rect; what Im looking to do is to buck that trend. Thin-skinned. A rock particle (top) from asteroid Itokawa (bottom) has layers (I and II) whose nano-blobs (light smudges) redden the asteroid.Published by AAAS on August 25, 2011www.sciencemag.orgDownloaded from www.sciencemag.orgSCIENCEVOL 33326 AUGUST 20111081NEWS&ANALYSISCREDITS (TOP TO BOTTOM): T. NOGUCHI ET AL., SCIENCE 333, 6046 (26 AUGUST 2011); COURTESY OF JAXA Astronomers had a problem. They knew that meteorites start out as parts of bigger rocks in space, mostly asteroids. But when they com-paredthespectralcolorsofasteroidswith those of the most common kind of meteorite that falls to Earth, they couldnt nd a match. NowJapaneseresearchershavefoundthe answer in the rst bits of asteroid returned to Earth by a spacecraft. Dissecting the samples, they have nailed the source of Earths most common meteorites and gotten to the root of astronomers color problem. The blast of the solar wind and perhaps other space weath-ering processes, it turns out, alteredthespectralcolorof themostcommontypeof asteroidsintheinneraster-oid beltthe S typesand masked their true nature.Mostplanetaryscien-tists,afterclose-upbutstill nothands-oninspectionof asteroids,hadconcluded that exposure to the rigors of spacemustalterthesurface ofS-typeasteroidsbutthe hard proof still wasnt there. Then, in June 2010, Japans Hayabusa space-craft returned a sample of the S-type asteroid Itokawa. In March at the Lunar and Plane-tary Science Conference (Science, 15 April, p. 302), Japanese researchers presented their elemental, isotopic, and mineralogical anal-ysesof50Itokawaparticlessmallerthan 100micrometers.Theyreportthoseand additional analyses in detail in this issue of Science (pp. 1113-1130).ThematchbetweenItokawaandthe mostcommontypeofmeteoriteonEarth, the ordinary chondrites, is right on, just as astronomerspredicted. Thatresultbrings an irrefutable closure to the long-standing S asteroid conundrum, says asteroid spe-cialistClarkChapmanoftheSouthwest Research Institute in Boulder, Colorado.Remotesensing,however,couldnt revealwhatcreatedthedeceptivealtera-tion. For that, Hayabusa analysts used scan-ningtransmissionelectronmicroscopy (STEM) to examine vanishingly thin slices of 10 Itokawa rock particles that averaged 52micrometersindiameter.Theywere lookingfornanoblobsthatareopaque and about the same size as the wavelength of light so they could scatter light and make Itokawa look redder, at least to the supersen-sitive eye of a spectrometer. That sort of red-dening is what misled the astronomers.Ontherimsoffiveoftheparticles, TakaakiNoguchiofIbarakiUniversityin Japan and 17 colleagues found two thin lay-ers. The outer, surface layer was only 5 to 15nanometersthickandcontained1-to 2-nanometer-wide blobs of iron sulde. To judge by the STEM images, the outer layer and its iron-sulde nanoblobs formed when micrometeorite impacts, solar wind, or both vaporizednearbymineralsandthevapor condensedontothe rock particle.I mme d i a t e l y beneaththeouter layerofiron-rich Itokawaparticles wasanotherlayer, 20 to 50 nano meters thick,containing only metallic iron nanoblobs. These blobs must have been formed by solar wind when charged particles such as protons penetrated Itokawa rock particles. Unless the outer lay-ersiron-sulfidenanoblobshaveanunex-pectedlylargeeffectonlight,thesemore abundant metallic iron nanoblobs created by solar wind may be the major cause of the spectralmodificationofItokawa,writes Noguchi in an e-mail. So S-type asteroids seem to have gotten a sunburn from sitting too long in the wind of deep space. Their skin was so reddened that for decades the parents of terrestrial meteorites went unrecognized.RICHARD A. KERRHayabusa Gets to the Bottom of Deceptive Asteroid CloakingPLANETARYSCI ENCEto make sure we have the interdisciplinarity to make us competitive. Q: TheEuropeanResearchCouncilhasa good reputation, but the quality of other European Commission research programs has been criticized. Is it improving?L.B.:ThereareissuesthatIwouldhave with some of the directions Europe is tak-ing: for example, how on Earth the priori-ties for the European Institute of Technology are being set without seemingly any consul-tationwiththeacademiccommunity(see p. 1090). But engagement with Europe, both with the commission and through bipartite arrangements with universities in Europe, is a very important way forward. Were among the lead universities in Europe, and I think we should take on that leadership role and extend it into Europe to work hand-in-glove with partners in Germany and France and other European countries. Q: Whats your strategy for Asia? Will you open campuses there?L.B.: Weve tied our research strategy and our international strategy together. We do not see that that strategy is going to involve awholesaleexpansionofundergraduate education, nor do we see extra undergrad-uate campuses as being necessary. But our efforts in research are going to be far more inter national; they are going to be focused on direct interactions with the Far East, just as much as with North America and Europe. Q:Willyoulookatremoteresearch campuses?L.B.: Yes, we willwhen we have a critical massofinvestigator-ledresearchthathas reachedapointwhereinstitutional-level support is appropriate. We are now identi-fying areas where we should move towards institution-levelinteraction.Ivebeento China twice and Singapore twice this year, once to India in spring and Im going back again in September, to look at where such opportunitiesexist.Ibelievetopinterna-tional universities will gradually be working together. They can make a dent into these global problems, but it will be done on the basis of international cooperation. Were not going to nd solutions to global warming instantaneously.Q: Havent previous attempts to build inter-national partnerships between universities tended to zzle?L.B.: Historically what you say may be cor-rect; what Im looking to do is to buck that trend. Thin-skinned. A rock particle (top) from asteroid Itokawa (bottom) has layers (I and II) whose nano-blobs (light smudges) redden the asteroid.Published by AAAS on August 25, 2011www.sciencemag.orgDownloaded from www.sciencemag.orgSCIENCEVOL 33326 AUGUST 20111083NEWS&ANALYSISCREDIT: ADAPTED FROM CAMILO MORA With apologies to Jonathan Swifts famous ea-ridden 1733 poem, biologists typically donotbelievelifeonEarthproceedsad innitum. The planet must hold a limited, notinfinite,numberofplants,animals, fungi, and other complex species. But as sci-entists have tried to pin down that number for close to 2 centuries, their estimates have ranged wildly from fewer than a million to about 100 million. Now, a novel type of anal-ysis, which takes advantage of an apparently natural mathematical pattern in the biodiver-sity produced by evolution, has settled on a tally of about 8.7 million eukaryotic species, give or take a million. Many researchers nd the case for this latest estimate, outlined online 23 August in PLoS Biology, convincing, though not the nalword.Itsdenitelyanimaginative new method, says Robert May of the Uni-versity of Oxford in the United Kingdom, who wrote a commentary accompanying the study and has previously put forth his own predictions regarding the extent of the plan-ets biodiversity. But all methods are neces-sarily approximate.Biologist Edward O. Wilson of Harvard Universitysuggeststhatthestudymight undershootthemark,however,although he admires the attempt to provide an inno-vative way of calculating the planets total biodiversity. We should keep doing it, but we should be always suspicious, he says. Undiscovered species tend to be undiscov-eredforareason,Wilsonnotestheyre rare, isolated, and, consequently, probably a lot more diverse than many suspect. Explor-ing this unknown diversity will be one of the greatest areas of biology awaiting us this century, Wilson adds, especially because scientists are in a race to discover species before they go extinct.One of the rst to pursue scientic esti-mates of species numbers was Oxford ento-mologist John Obadiah Westwood in 1833. He surveyed the extrapolations of many of his early colleagues, based on current taxo-nomic collections, reporting an estimate that about half a million insect species possibly lived on Earth. In 1982, Terry Erwin, a taxonomist at the Smithsonian National Museum of Natural History, took a new, experimental tack and got a much bigger number: He and his col-leagues gassed 19 trees in a jungle in Pan-ama,collectingabout1000uniquebeetle species.Usingasetofassumptionsstill hotly debated today, Erwin calculated that tropical beetles and their arthropod relatives alone constituted 30 million species. Erwin launched a boom of research into biodiversity,buthisanalysisandsimilar ones that followed suffered from the same aw, says marine biologist Boris Worm of DalhousieUniversityinHalifax,Canada: Theycouldntbetested. Theresnoway unless you go out and count all the beetles, Worm says. Whiletryingtotallythenumberof organisms in the sea as part of the Census of Marine Life, Worm and his colleagues stum-bled on a taxonomic pattern that seemed to resolve this dilemma. With each step down inLinnaeussfamousclassificationsys-tem, the number of classes, orders, and so on tended to creep up in a predictable man-ner, his team realized. The kingdom Anima-lia, for instance, hosts 32 recorded phyla, 90 classes, 493 orders, 5404 families, and 94,240 genera. Extending that growth curve out,Wormandhiscolleaguespredicted there should exist some 7,770,000 animal specieseventhoughtaxonomistshave identied only about 950,000 so far. Plants, fungi,andothereukaryotestotalabout 1 million other species, they also predict.The researchers validated their taxonomic approach by comparing estimates made this waywithrealspeciescountsfromwell-known evolutionary branches, such as mam-mals and birds. Our predictions were very, very close to the true numbers, says study co-author Camilo Mora, a marine ecologist at the University of Hawaii, Manoa. If their 8.7 million species estimate is valid, Mora and his colleagues note, taxonomists have yet to catalog nearly 90% of land- and ocean-dwellingeukaryotes.(Theteamstrayed away from crunching a total for bacteria and archaea because scientists still puzzle over how to categorize species for the microbes.) Mora and Worms study highlights that scientistsaregettingclosertopinpoint-ingEarthsvastbiodiversity,saysNigel Stork, a biologist at Grifth University in Queensland, Australia.Lastyear,heand colleaguesusedacombinationofbeetle counts made in New Guinea and complex mathematicalmodelingtoestimatethat there are some 3.7 million arthropod spe-cies on Earth. Despite the radically differ-ent method, much more akin to Erwins early work, Storks estimate falls in line with what Mora and Worm found: We are beginning to home in, Stork says. Many still argue that a tally of 8.7 mil-lion species sells our planet short. Taxono-mists have only brushed the surface of the diversity of many microscopic organisms suchasyeasts,cautionsStevenStephen-son, an ecologist who specializes in fungi at the University of Arkansas, Fayetteville. He suspects that the PLoS Biology study under-estimatesthediversityoftheseandother eukaryotic microbes.And the analysis may have a more funda-mental aw, some suggest. The relationship between levels in Linnaeuss classication system is a statistical pattern, not one based on sound scientic principles, says Lucas Joppa, a conservation ecologist at Microsoft Research in the United Kingdom. Theres noinherentecologicalrationaleforwhy kingdom should be to phylum as phylum is to class, Joppa says.Erwin agrees and says that hes inclined not to set a limit on species numbers at all. The more he digs into the Amazon, the more itlooksliketheinsectspeciesthere,like Swifts eas, dont have a nite end. Bio-diversity is innite, he says. And there is no way to estimate the innite.DANIEL STRAIN8.7 Million: A New Estimate for All The Complex Species on EarthBI ODI VERSI TY3290493540494,240953,43410,000,0001,000,000100,00010,0001,00010010ADDING UP ANIMALSNumber of described groups1. Phylum2. Class3. Order4. Family5. Genus6. SpeciesPhylumClassOrderPredictedDescribed/CatalogedFamilyGenusSpeciesKINGDOM ANIMALIA1 2 3 4 5 6Predictive pyramid. Given the number of animal phyla,orders,families,andgenera,researchers predict that the kingdom has 7,770,000 species.Published by AAAS on August 25, 2011www.sciencemag.orgDownloaded from 26 AUGUST 2011VOL 333SCIENCEwww.sciencemag.org1084CREDITS (TOP TO BOTTOM): ANN GIBBONS; BENCE VIOLA/MPI EVA; ANN GIBBONS; BENCE VIOLA/MPI EVA DENISOVACAVE,SIBERIABenceViola rst saw the ancient molar last summer, just after a piece of it was dug out of layers full of brown dirt, gray rock, animal bones, stone tools, and goat feces. He considered the tooth fragments too big and weirdly shaped to be human. I thought it must belong to a cave bear, he says.Several fossils were found that summer in this remote cave in the Altai Mountains. Some, including a toe bone, looked human andweretobesentforDNAanalysisto paleogeneticistSvantePboattheMax PlanckInstituteforEvolutionary Anthro-pology in Leipzig, Germany. Viola, a post-doc at Max Planck, almost didnt include the molar. But he and Pbo decided to play it safe and test all the new fossils. The layer that held the molar in Denisova Cave was also the resting place of a girls nger bone, whichwassowellpreservedthatPbos lab was able to sequence its nuclear genome and identify it as belonging to a previously unknown type of archaic human. The team calledthemtheDenisovans.Forthefirst time, researchers had a genome in search of a fossil record, so every possible new bone was signicant.BackinLeipzig,graduatestudent Susanna Sawyer was charged with extract-ing DNA from the animal bones. In June, she stopped Pbo in the hall. I think I found another Denisovan, she said. Preliminary analysis suggested that the molars DNA was similar to that of the cave girls. Pbo shook Sawyers handthis was only the third fossil ever found of a Denisovan, the others being the bit of nger bone and another molar, also from Denisova cave.Who Were the Denisovans? At an unusual meeting at a Siberian cave, researchers nd that these mysterious archaic humans lived in the same place as both modern humans and Neandertalsthough not necessarily at the same timeand their range probably stretched into east Asia Cave treasure. Researchers have found the tooth of a Denisovan, plus a sophisticated stone bracelet and tools, in Denisova Cave.NEWSFOCUSPublished by AAAS on August 25, 2011www.sciencemag.orgDownloaded from www.sciencemag.orgSCIENCEVOL 33326 AUGUST 20111085NEWSFOCUSBiyaChulyshmanKatunCharyshKoksaBashkausChuyaAnuiPeschanayaObDenisovaUst-KarakolKara-BomKaramaOkladnikovChagyrskayaStrashnaya0 60 kmCave siteOpen air siteBiyskGorno-AltayskNovosibirskK A Z A K H S TA NMO NG O L I AC H I NAAltai MountainsWhats more, preliminary analysis of the mitochondrial DNA from the toe bone sug-geststhatitbelongednottoaDenisovan but to a Neandertal. That means both types of archaic humans lived in the same cave. And the large, three-room cave also holds sophisticated stone tools and bone artifacts that appear to have been crafted by our own species,Homosapiens.Theoneplace wherewearesureallthreehumanforms have lived at one time or another is here in Denisova Cave, Pbo said.Today the cave is off the beaten path, in southernSiberia,350kilometersnorthof theRussianborderwithbothKazakhstan andMongolia,andclosertoBeijingthan Moscow.NowtheDenisovandiscoveries have shifted the spot-lightfromancient humansinAfrica, the Middle East, and Europe to those in this remotecornerofAsia. As Russian Academy of Sci-ences (RAS) archaeologist Anatoly Dereviankoputsit:Theworldis looking eastward.To that end, Derevianko and his RussiancolleaguesinvitedPbo and a select group of human origins researchers from different disciplines and countries to a remarkable sym-posiumatanarchaeologicalcamp nearDenisovaCaveinJuly. Their goalwastotrytosolvethemys-tery of the cave girls identity, to nd more of her people, and to explore howthediscoveryischallenging modelsofmodernhumanorigins. In lively discussions sometimes cat-alyzedbyvodkatoasts,theycom-paredwhatarchaeology,genetics, and fossils reveal about the world the Denisovans inhabited 30,000 to 50,000 years ago. Genomic data have already shown that our ancestors mingled with archaic humans, who may have given us valuable immune cell types (see sidebar, p. 1086). But its not clear when and where this happened.Invisible humanThe gathering gave Derevianko, director of the Institute of Archaeology and Ethnogra-phy at the RAS in Novosibirsk, a chance to showcasesomeoftheregionsimpressive archaeologicalsites. Driving off dirt roads in troop movers and along ruttedroadsininde-structibleUAZvans, the Russians took their visitors to a dozen digs. Some were caves at the edge of alpine forests of silver birch and Siberian larch; others were open-air sites in grassy mead-owsofbeebalm,wild mint, and edelweiss.Thetrailofancient humansstartswithH. erectus, which left prim-itivepebbletoolsin the Altai almost 800,000 years ago. After a hiatus whentheclimatewas frigid,thedescendants ofH.erectusreturned by300,000yearsago,leavingmoretools behind. Some kind of human has lived here ever since.Starting80,000to70,000yearsago, archaic humans began to use more modern methods to make tools at sites called Kara BomandUst-Karakol,where10%ofthe tools were blades or burins (a tool used to chisel wood); the Russians see this as the rst stirrings of modern human behavior here. From50,000to30,000yearsago, thearchaicpeoplehuntedbear,lynx,and wildboarinthe Altai Mountains, where they set up seasonal camps insummer,saidRAS archaeologistMikhail Shunkov as he led the tours. They retreated to limestone caves such as Denisova in winter. With a natural opening for a chimney, the cave was quite a cozy place, Shunkov said, point-ing to an opening in the ceiling at Denisova. With a clear view of the Anui Riverand any humans or animals passing belowDenisova must have been choice housing, said Pbo, noting how sunlight streaming through the opening overhead lit the cave like a chapel. It is kind of cool to imagine that the person whose genome was sequenced had seen these walls, he said.At about this time, at least two different types or local cultures of artifacts appear, one at Kara Bom and one at Ust-Karakol. The Russians consider both to be sophisticatedCREDITS (TOP TO BOTTOM): MAP ADAPTED FROM A. DEREVIANKO AND M. SHUNKOV, PALEONTOLOGICAL J. 43, 8 (2009); BENCE VIOLA/MPI EVA (2)Onlinesciencemag.orgPodcast interview with author Ann Gibbons.Meeting of the minds. Archaeologist Anatoly Derevianko (top) and paleo-geneticist Svante Pbo worked together to discover the Denisovans.Room with a view. Denisova Cave was such prime real estate, it attracted three kinds of humans.a.f Sci-gist AAnatolyPublished by AAAS on August 25, 2011www.sciencemag.orgDownloaded from 26 AUGUST 2011VOL 333SCIENCEwww.sciencemag.org1086NEWSFOCUSCREDIT: ABI-RACHED ET AL., SCIENCE (ADVANCED ONLINE EDITION) culturestraditionallyassociatedwithonly H.sapiens.Similarlyadvancedartifacts appear at the same time in Denisova, with stonebladeletsusedonspears;pendants made of teeth of fox, bison, and deer; and even a bracelet made of a mineral found hun-dreds of kilometers away. Until recently, the archaeologistshadnodoubtsthatpeople associated with this industry were anatomi-callymodern,Dereviankosays.Butnow, thanks to the genomic results, its possible that some were Denisovans, Shunkov says.To identify the toolmakers, researchers need fossils, but they are few and far between. As a result, it remains unknown what the Denisovan looked like or how he behaved, saysbiologicalanthropologistMaria MednikovaoftheRASinMoscow.So Violas talk at the meeting, describing the single new tooth, drew intense interest. Like therstmolarfound,itisverylargeand lacks specialized features found in Neander-tals. Nor does the tooth resemble a modern human molar, as it has many unusual cusps, Viola says. The nger bone fragment that rst yielded Denisovan DNA was so small that it yielded little information other than it was a childs because the growth plate was not fused.In addition to the few Denisovan fossils, Neandertals also left fossils and characteris-tic Mousterian stone points and scrapers in Denisova and other caves. At the meeting, Russian researchers described new nds of Neandertaltoolsandfossilsincavesjust 100 and 150 kilometers away from Denisova Cave, dated to 45,000 years ago. Mednikova adds that the toe bone from Denisova looks most like a Neandertal toe from Iraq, tting well with the preliminary DNA nding. And yetDereviankothinksNeandertalsdidnt stay long here, because their bones and arti-factsdisappearby40,000yearsago.He views them as brief visitors, probably com-ing from the west in Kazakhstan. Neighbors, or successors? ItisnowclearthatNeandertals,Deniso-vans,andmodernhumansonceoccupied the Altaibutweretheyallthereatthe same time? This is hard to answer because there are questions about the dating of cru-cial layer 11 in Denisova Cave. This meter-thicklayerheldtheDenisovanngerand molars,theNeandertaltoe,andthemod-ernhumanartifacts,althoughsomewere found in different galleries of the cave. The bones and teeth are too fragmentary to be dateddirectly.Butradiocarbondatingof sevenanimalboneswithcutmarksfrom layer 11 provides dates of 50,000 years or older in both galleries. Yet the layers young-estsedimentsdatetoaslateas16,000to 30,000 years ago, as reported in December in Nature. Thus layer 11 has artifacts from at least two different periods. And, in the south gallery near the spot where the nger bone was found, an obvious wedge of disturbed sediment suggests some mixing.For now, Derevianko and colleagues pro-posesequentialoccupations: TheDeniso-vanswereinthecaveabout50,000years ago,Neandertalscameinbrieflyabout A Denisovan Legacy in the Immune System? Everybody knows about the dangers of inbreeding (see Hapsburg dynasty, collapse of). In fact the reproductive strategies of many animals are based on avoiding it, as when female chimpanzees move out of their birth groups to mate. Last year, researchers showed that human ancestors took that strategy to its limits by breeding with the now-extinct Neandertals and Denisovans (Science, 28 January, p. 392). Now a study published online in Science this week (http://scim.ag/Abi-Rached) suggests that such mating was benecial, boosting the immune systems of early Europeans and Asians and leaving a valuable legacy in the genes of many people alive today. This is the rst sug-gestion that something that came from archaic hominins into modern humans conferred an advan-tage, says paleogeneticist Svante Pbo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.Genomic data from fossils thus far suggest that living people carry only small amounts of archaic DNA. Only 2% to 7% of the DNA of todays Europeans and Asians apparently came from the ancient Denisovans and Neandertals (seemaintext).Thenewpaperexam-ines Europeans and Asians and nds that archaic people contributed more than half of the alleles that code for proteins made by the human leukocyte antigen system (HLA),whichhelpstheimmunesystem recognizepathogens.Archaicalleles have signicantly shaped modern human immunesystems,wrotePeterParham and Laurent Abi-Rached of Stanford Uni-versity in Palo Alto, California. Immunogeneticist Parham has spent 16yearspuzzlingovertheevolutionof one rare HLA allele, called HLA-B*73. This variant is quite different from others but is similar to alleles in the same position in the genomes of chimps and gorillas. So it seems to be ancient, perhaps arising long before our ancestors split from gorillas about 16 million years ago. Yet today, B*73 is concentrated in western Asia, where modern humans have lived for less than 90,000 years, and it is absent from African tribes who usually carry the most ancient gene lineages.While studying this allele, Parhams team got a big break last year when Pbos team pub-lished the complete genome of the Denisovan cave girl. She didnt carry B*73and it hasnt been found in Siberiabut she carried two other linked HLA-C variants, which occur on the same stretch of chromosome 6. If living people have any of these variants, they almost always carry at least two of the three variantsas did the cave girl. So even though she lacked B*73, the researchers pro-pose that all three variants were inherited, often in pairs, from archaic humans in Asia. The Deniso-vans are the prime suspects, given their presumed distribution in Asia. The team also examined other HLA alleles in three Neandertals and one Denisovan and found several other ancient variants that today show up in living Asians or Europeans. Parham thinks these variants were benecial and so, once acquired from archaic people, spread rapidly in small but expanding modern populations. The fact [that these genes] may have been parachuted into modern humans is an attractive interpretation, says immunologist John Trowsdale of the Univer-sity of Cambridge in the United Kingdom. However, others are not quite convinced that the alleles came from archaic humans. Parhams team hasnt completely ruled out other explanations for the gene distributions, such as certain types of selection, says geneticist David Reich of Harvard University. Regardless, he says, I am happy to see people using archaic genomes for different kinds of analyses.A.G.Ancient roots. The allele HLA-B*73, today mostly seen in west Asia, may come from Denisovans.Published by AAAS on August 25, 2011www.sciencemag.orgDownloaded from www.sciencemag.orgSCIENCEVOL 33326 AUGUST 20111087NEWSFOCUSCREDITS (TOP TO BOTTOM): ANN GIBBONS; MARIA DOBROVOLSKAYA; ANN GIBBONS45,000 years ago, and modern humans fol-lowed.Buttheresearchersagreethatthe microstratigraphyofthecaveneedsmore analysis. They are redating layer 11 with radio-carbon on more cut-marked animal bones.Overall, Derevianko and his colleagues see a gradual, local evolution of H. erectus into H. sapiens in the Altai, with a brief intru-sion of Neandertals and Denisovans. This ts a minority view of human origins, called multiregionalism,whichpositsthatthe descendantsofH.erectusevolvedinto Neandertalsandmodernhumansand, apparently,Denisovansindifferent regions. Then humans coming out of Africa mingled with the other groups and H. sapi-ensemerged worldwide. As Russian and Chinese archaeologists raised their glasses to toast regional conti-nuity,however,severalgeneticistsshifted uncomfortablyorevenquietlydemurred: Thattheoryisincontrasttothelong-prevailingviewthatH.sapienswasborn in Africa and swept the globe, wiping out localarchaicpeoples. Andinlightofthe genomicdata,mostgeneticistsnowhold amiddle-of-the-roadviewthatmodern humans arose in and spread out of Africa, then interbred with local archaic peoples to a limited degree (Science, 28 January, p. 392). If you write that I drank a toast to [regional] continuity, Ill kill you, one geneticist told a reporter. Butthegeneticistsdoagreewiththe Russians that modern humans mingled with both Neandertals and Denisovans. Pbos teamfoundin2010thatlivingEurope-ans and Asians have inherited about 2.5% oftheirDNAfromNeandertals(Science, 7 May 2010, pp. 680 and 710) and thatlivingMelanesianscarryan additional 5% of Denisovan DNA. If modern humans interbred with Neandertals, researchers speculated that fossils of each group, about the sameageandfoundclosetoeach other in Israeli caves, represented the groups who mixed sometime before 90,000yearsago.Thosemodern people carrying a small amount of NeandertalDNAthensplitintoat least two groupsone that headed into Europe to replace the Neander-tals there, and a second group that headedintoAsiatomixwiththe Denisovans, says population geneti-cist David Reich of Harvard Medical School in Boston. At the meeting, the DNA research-ersofferedsomenewinsightsinto this story. They found that the three Denisovans, all from one cave, had more vari-ation in their mtDNA than did seven Neandertals from western Europe toSiberia,Sawyerreported. This and another report at the meetingthatAustralianAborigines,like Melanesians,haveinherited5% of their DNA from Denisovanssuggests that the Denisovan home range once stretched far beyond the Altai, into eastern Asia. This tells usthattheDenisovanshadlarge populationsizes,despitetheir punyfossilrecord,Pbosays.It also shows that Denisovans and the ancestors of Melanesians must have interbred before 40,000 to 60,000 yearsago,when Aboriginesfirst settled Australia.As for the timing of the Nean-dertal-humanmixing,thenewest analyses tend to push that younger. PopulationgeneticistMontgom-erySlatkinoftheUniversityof California,Berkeley,saidthat hismodelrunsgavehimawide range of preliminary results, from 65,000 years to 45,000 years ago, but hes still working the numbers. Reich reported that his independent analysesalsosuggestayounger date. If the mixing happened more recentlythan90,000yearsago,it rules out the Israeli fossils as repre-sentatives of the groups who mixed. Others, such as Derevianko and paleoanthropologist John Hawks of the University of Wisconsin, Mad-ison, interpret the genetic data dif-ferently. They think that even small amounts of interbreeding conrm the regional conti-nuity model, and that there was more mixing in the past, but its traces were erased by later waves of immigrants who swamped out the archaic genes. To help decide among these models, sev-eralgroupsaresearchingforDenisovans beyond Denisova, as far east as China, where Pbo is now analyzing fossil DNA. As Pbo climbed down a ladder into a oodlit pit at Denisova and bent his lanky frame low to get a good look at layer 11, a colleague shouted: Grab a trowel, Svante. Pbo didnt. But liketheothers,heisconvincedthatall types of datagenetic, archaeological, and fossilwill have to be integrated in order to tell the story of the Denisovans and so of our own species. Were beginning to clarify history in eastern Eurasia, Pbo said, and Im sure that in the next few years, there will be more discoveries.ANN GIBBONSOn tour. Archaeologist Mikhail Shunkov showcased the many archaeological sites of the Altai Mountains.Teamwork. Anthropologist Maria Mednikova (top) analyzed fossils,andgeneticistsSusannaSawyerandDavidReich studied the DNA of the ancient Denisovans.Published by AAAS on August 25, 2011www.sciencemag.orgDownloaded from 26 AUGUST 2011VOL 333SCIENCEwww.sciencemag.org1086NEWSFOCUSCREDIT: ABI-RACHED ET AL., SCIENCE (ADVANCED ONLINE EDITION) culturestraditionallyassociatedwithonly H.sapiens.Similarlyadvancedartifacts appear at the same time in Denisova, with stonebladeletsusedonspears;pendants made of teeth of fox, bison, and deer; and even a bracelet made of a mineral found hun-dreds of kilometers away. Until recently, the archaeologistshadnodoubtsthatpeople associated with this industry were anatomi-callymodern,Dereviankosays.Butnow, thanks to the genomic results, its possible that some were Denisovans, Shunkov says.To identify the toolmakers, researchers need fossils, but they are few and far between. As a result, it remains unknown what the Denisovan looked like or how he behaved, saysbiologicalanthropologistMaria MednikovaoftheRASinMoscow.So Violas talk at the meeting, describing the single new tooth, drew intense interest. Like therstmolarfound,itisverylargeand lacks specialized features found in Neander-tals. Nor does the tooth resemble a modern human molar, as it has many unusual cusps, Viola says. The nger bone fragment that rst yielded Denisovan DNA was so small that it yielded little information other than it was a childs because the growth plate was not fused.In addition to the few Denisovan fossils, Neandertals also left fossils and characteris-tic Mousterian stone points and scrapers in Denisova and other caves. At the meeting, Russian researchers described new nds of Neandertaltoolsandfossilsincavesjust 100 and 150 kilometers away from Denisova Cave, dated to 45,000 years ago. Mednikova adds that the toe bone from Denisova looks most like a Neandertal toe from Iraq, tting well with the preliminary DNA nding. And yetDereviankothinksNeandertalsdidnt stay long here, because their bones and arti-factsdisappearby40,000yearsago.He views them as brief visitors, probably com-ing from the west in Kazakhstan. Neighbors, or successors? ItisnowclearthatNeandertals,Deniso-vans,andmodernhumansonceoccupied the Altaibutweretheyallthereatthe same time? This is hard to answer because there are questions about the dating of cru-cial layer 11 in Denisova Cave. This meter-thicklayerheldtheDenisovanngerand molars,theNeandertaltoe,andthemod-ernhumanartifacts,althoughsomewere found in different galleries of the cave. The bones and teeth are too fragmentary to be dateddirectly.Butradiocarbondatingof sevenanimalboneswithcutmarksfrom layer 11 provides dates of 50,000 years or older in both galleries. Yet the layers young-estsedimentsdatetoaslateas16,000to 30,000 years ago, as reported in December in Nature. Thus layer 11 has artifacts from at least two different periods. And, in the south gallery near the spot where the nger bone was found, an obvious wedge of disturbed sediment suggests some mixing.For now, Derevianko and colleagues pro-posesequentialoccupations: TheDeniso-vanswereinthecaveabout50,000years ago,Neandertalscameinbrieflyabout A Denisovan Legacy in the Immune System? Everybody knows about the dangers of inbreeding (see Hapsburg dynasty, collapse of). In fact the reproductive strategies of many animals are based on avoiding it, as when female chimpanzees move out of their birth groups to mate. Last year, researchers showed that human ancestors took that strategy to its limits by breeding with the now-extinct Neandertals and Denisovans (Science, 28 January, p. 392). Now a study published online in Science this week (http://scim.ag/Abi-Rached) suggests that such mating was benecial, boosting the immune systems of early Europeans and Asians and leaving a valuable legacy in the genes of many people alive today. This is the rst sug-gestion that something that came from archaic hominins into modern humans conferred an advan-tage, says paleogeneticist Svante Pbo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.Genomic data from fossils thus far suggest that living people carry only small amounts of archaic DNA. Only 2% to 7% of the DNA of todays Europeans and Asians apparently came from the ancient Denisovans and Neandertals (seemaintext).Thenewpaperexam-ines Europeans and Asians and nds that archaic people contributed more than half of the alleles that code for proteins made by the human leukocyte antigen system (HLA),whichhelpstheimmunesystem recognizepathogens.Archaicalleles have signicantly shaped modern human immunesystems,wrotePeterParham and Laurent Abi-Rached of Stanford Uni-versity in Palo Alto, California. Immunogeneticist Parham has spent 16yearspuzzlingovertheevolutionof one rare HLA allele, called HLA-B*73. This variant is quite different from others but is similar to alleles in the same position in the genomes of chimps and gorillas. So it seems to be ancient, perhaps arising long before our ancestors split from gorillas about 16 million years ago. Yet today, B*73 is concentrated in western Asia, where modern humans have lived for less than 90,000 years, and it is absent from African tribes who usually carry the most ancient gene lineages.While studying this allele, Parhams team got a big break last year when Pbos team pub-lished the complete genome of the Denisovan cave girl. She didnt carry B*73and it hasnt been found in Siberiabut she carried two other linked HLA-C variants, which occur on the same stretch of chromosome 6. If living people have any of these variants, they almost always carry at least two of the three variantsas did the cave girl. So even though she lacked B*73, the researchers pro-pose that all three variants were inherited, often in pairs, from archaic humans in Asia. The Deniso-vans are the prime suspects, given their presumed distribution in Asia. The team also examined other HLA alleles in three Neandertals and one Denisovan and found several other ancient variants that today show up in living Asians or Europeans. Parham thinks these variants were benecial and so, once acquired from archaic people, spread rapidly in small but expanding modern populations. The fact [that these genes] may have been parachuted into modern humans is an attractive interpretation, says immunologist John Trowsdale of the Univer-sity of Cambridge in the United Kingdom. However, others are not quite convinced that the alleles came from archaic humans. Parhams team hasnt completely ruled out other explanations for the gene distributions, such as certain types of selection, says geneticist David Reich of Harvard University. Regardless, he says, I am happy to see people using archaic genomes for different kinds of analyses.A.G.Ancient roots. The allele HLA-B*73, today mostly seen in west Asia, may come from Denisovans.Published by AAAS on August 25, 2011www.sciencemag.orgDownloaded from 26 AUGUST 2011VOL 333SCIENCEwww.sciencemag.org1088NEWSFOCUSThe notion that tissue engineers can provide a stock of lab-grown body parts to replace faultytissuesisstill,forthemostpart,a dream. Ready-made hearts, livers, or kid-neys that could ease the shortage of donor organs will not be available in the clinic any-time soon. But recent progress suggests the dream is not completely beyond reach. Lab-grown bladders are functioning in dozens of patients in the United States, and doctors inEuropehaveimplantedlab-growntra-cheas into several patients. In Japan, several dozen children and young adults born with severe heart defects are living with tissue-engineered cardiac blood vessels. The rst received implants 10 years ago. They go to school,holdfull-timejobs,playsportsinshort,saysChristopherBreuer,oneof the implants developers, they live active, healthy lives. This month, after an arduous approval process, surgeons are testing the blood vessels in the rst U.S. patients. TheU.S.trialmarksanimportant signpostforthewholeeld,saysJoseph Vacanti,atransplantsurgeonandtissue engineer at Massachusetts General Hospital in Boston. The implants, which are used to connect a major cardiac vein and the artery that carries blood to the lungs, are made of a synthetic scaffold seeded with cells from the patients own bone marrow. In the body, the graft develops into a living blood vessel that grows with the patient. Theengineeredvesselsweredevel-oped by a group at Yale University led by Breuer, a pediatric surgeon, and Toshiharu Shinoka, a cardiosurgeon. Although getting approval for the trial from the U.S. Food and Drug Administration (FDA) took more than 4 years and generated more than 3000 pages of documents, the process paid off, Breuer says: Recent animal studies, arising in part from questions the FDA asked, have turned some of Breuer and Shinokas assumptions upside down, leading to a better understand-ing of how the graft works and ideas for how to improve it.Thenewexperimentssuggestthat inflammation,longseenasanenemyof transplantsandartificialimplantsalike, seems to play a key role in the transforma-tion of the cell-lled scaffold into a healthy blood vessel. And stem cells, which have been seen as the stars of tissue engineering, play a less signicant role than expected. The results are prompting tissue engineers to rethink the role of inammation and stem cells,saysAnitaDriessen-Mol,atissue engineer at Eindhoven University of Tech-nology in the Netherlands. Its very inspir-ing work, she says.Replumbing the heartThe lab-made blood vessels are meant for children whose severely malformed hearts areunabletosupplytheirbodieswith enoughoxygen. Atbirththechildrenare known as blue babies for the skin tint that results. Unlike children with a normal heart, whichhastwoblood-pumpingchambers, or ventricles, these children have only one working ventricle. Without a repair, Breuer says, 70% of children with such defects will die before their rst birthday. Inthelate1960s,thesurgeonFrancis Fontan and his colleagues developed a tech-nique to make such hearts more efcient. Theyrearrangedtheorgansplumbingto concentratepumpinginthesinglefunc-tioning ventricle. Over the years, surgeons haveimprovedtheprocedurebyaddinga length of blood vessel to better connect the heartsinferiorvenacava,whichcollects blood from veins in the lower body, to the pulmonary artery, which leads to the lungs, bypassing the heart (see diagram). In a few cases, surgeons can build this diversionary vesselfromthepatientsowntissue.But often there isnt enough tissue available, and surgeonsusetubesofsyntheticmaterials such as Gore-Tex. Suchartif icialbloodvesselshave significantdrawbacks,Breuersays.The grafts can become calcied, trigger blood clots,and,ifcellsbuildupontheinside, can develop stenosis, a dangerous narrow-ing of the vessel. And because the synthetic graft doesnt grow with the child, surgeons CREDITS: (TOP) ADAPTED FROM J. D. ROH ET AL., PNAS 107, 10 (9 MARCH 2010) NATIONAL ACADEMY OF SCIENCES; (BOTTOM) B. STRAUCH/SCIENCEMending the Youngest HeartsResearchers have begun implanting tissue-engineered blood vessels into toddlers with heart defects, and new studies of the grafts in animals show they work in unexpected waysTI SSUEENGI NEERI NGLifesaving implant. A graft bypasses the heart, redirecting low-oxygen blood from the inferiorvena cava directly to the pulmonary artery.Biodegradable scaffold. Bone marrow cells seeded on a synthetic frame attract immune cells; these signalnearby vessels to grow into and over the graft.Published by AAAS on August 25, 2011www.sciencemag.orgDownloaded from www.sciencemag.orgSCIENCEVOL 33326 AUGUST 20111089NEWSFOCUSmusteitherdelaysurgeryuntiltheheart has grown larger or implant a graft that is initi