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FOOD TECHNOLOGY EXPLORATION Preserving Wines Motion Microscopes’ Precision Tools Findas Clımate Changes Powerful New Vıew Sunken Treasures ScientificAmerican.com JANUARY 2015TEBHPTlhuafaohennretearttsntther “Superhabitable” worlds may be common in our galaxy, making ideal homes for extraterrestrial life © 2014 Scientific American
ON THE COVER January 2015, Volume 312, Number 1 Alien life could exist not only on Earth-like planets but also on worlds quite different from our own. The misty world here is an Earth-mass moon of a gas-giant planet, which lurks in the background, accompanied by a smaller, lifeless moon. Light, heat and tidal forces from the giant planet could all sculpt the cloudy moon into a place even more hospitable for life than Earth. Illustration by Ron Miller. 52COURTESY OF CSABA PINTÉR, 2014 OLYMPUS BIOSCAPES DIGITAL IMAGING COMPETITION FEATURE S FOOD (spore-forming bodies of the moss Tortula ruralis) ASTRONOMY 60 Will We Still Enjoy Pinot Noir? 32 Better Than Earth Winegrowers are trying to preserve the taste of your favorite reds and whites as climate change Planets and moons that differ from Earth may make ideal alters the flavor compounds in grapes. homes for life beyond the solar system. By René Heller By Kimberly A. Nicholas MEDICINE E X P L O R AT I O N 40 A Weakness in Bacteria’s Fortress 68 In Search of Sunken Treasure Evolutionary biologists are pursuing an innovative Scientists are using exotic technologies to discover strategy to fight infection: attack the cooperative side and excavate underwater shipwrecks with of microbes. By Carl Zimmer the precision of an archaeological dig. By Philip J. Hilts TECHNOLOGY NEUROSCIENCE 46 A World of Movement 76 Why We Have Free Will A new tool makes astonishing movies of otherwise imperceptible motions. By Frédo Durand, William T. Yes, neurons fire in your head before you become aware Freeman and Michael Rubinstein that you have made a decision. But this discovery does not mean that you are a “biochemical puppet.” BIOLOGY By Eddy Nahmias 52 Living Large Microscopes find beauty in the most unexpected places. By Kate Wong January 2015, ScientificAmerican.com 1 © 2014 Scientific American
DEPARTMENT S 4 From the Editor 6 Letters 10 Science Agenda Time to test science-driven methods to cool our climate—before global warming forces ill-considered action. By the Editors10 12 Forum How the digital economy could lead to secular stagnation. By Carl Benedikt Frey 13 Advances nasa’s quest to bag an asteroid. The elusive sterile neutrino. Oppressive parenting. Where Ebola suits are made. 28 The Science of Health Do rare disorders lurk in your DNA? By Dina Fine Maron 31 TechnoFiles Can personal fitness monitors whip us—and health research—into shape? By David Pogue 82 Recommended Astronomical images through the ages. The origin of numbers. Brains in formaldehyde. Living with OCD. B y Clara Moskowitz13 83 Skeptic What the living dead can teach us about ancient prejudices. By Michael Shermer 84 Anti Gravity The bigger they are, the longer they burn. By Steve Mirsky 85 50, 100 & 150 Years Ago 86 Graphic Science Twitter, mainstream media and academic blogs focus on surprisingly different science topics. By Mark Fischetti SPECIAL REPORT S1 Haemophilia Therapy for this bleeding disorder requires frequent injec- tions and costs a lot. Now various other treatments are82 being developed, and gene therapy could offer a cure. This report, from Nature, highlights the latest research.Scientific American (ISSN 0036-8733), Volume 312, Number 1, January 2015, published monthly by Scientific American, a division of Nature America, Inc., 75 Varick Street, 9th Floor, New York, N.Y. 10013-1917. Periodicals postage paidat New York, N.Y., and at additional mailing offices. Canada Post International Publications Mail (Canadian Distribution) Sales Agreement No. 40012504. Canadian BN No. 127387652RT; TVQ1218059275 TQ0001. Publication MailAgreement #40012504. Return undeliverable mail to Scientific American, P.O. Box 819, Stn Main, Markham, ON L3P 8A2. Individual Subscription rates: 1 year $39.97 (USD), Canada $49.97 (USD), International $61 (USD).Institutional Subscription rates: Schools and Public Libraries: 1 year $72 (USD), Canada $77 (USD), International $84 (USD). Businesses and Colleges/Universities: 1 year $330 (USD), Canada $335 (USD), International $342 (USD).Postmaster: Send address changes to Scientific American, Box 3187, Harlan, Iowa 51537. Reprints available: write Reprint Department, Scientific American, 75 Varick Street, 9th Floor, New York, N.Y. 10013-1917;fax: 646-563-7138; [email protected] Subscription inquiries: U.S. and Canada (800) 333-1199; other (515) 248-7684. Send e-mail to [email protected] Printed in U.S.A.Copyright © 2014 by Scientific American, a division of Nature America, Inc. All rights reserved.2 Scientific American, January 2015 © 2014 Scientific American
From the Editor Mariette DiChristina is editor in chief of Scientific American. Many Worldss I type this essay on a flight from Dubai to Paris, I can see the Follow her on Twitter @mdichristina hazy curve of our blue planet at the horizon. I’ve just finished the kickoff meeting of the World Economic Forum’s Global Agenda Councils, where I served as vice chair of the Meta-Council on Emerg-A ing Technologies. I am now headed to the launch of the UNESCOWorld Library of Science, a set of free science resources for educators and studentscreated by a partnership of UNESCO and Nature Education, with funding supportfrom Roche. (Scientific American is part of Nature Publishing Group.) Althoughthey are using different approaches to tackle separate goals, both initiatives share abroader mission: to help improve the state of the world. I find myself reflecting: Earth is not without its problems, but it’s still themost habitable spot in the cosmos. Or is it? That is the intriguing possibility posed by this issue’s cover story, “BetterThan Earth,” by René Heller. “Over the past two decades astronomers havefound more than 1,800 exoplanets [beyond our solar system], and statistics sug-gest that our galaxy harbors at least 100 billion more,” Heller writes. Some of them may be “superhabitable” worlds—with stable biospheres thatmay be optimal targets in our search for extraterrestrial life in other corners ofthe galaxy. They may even surpass the ability to nurture life that we see on Earth,with its vast deserts, frigid polar regions and nutrient-poor open oceans. In ourplanet’s past, it was warmer, wetter and more oxygen-rich than today, and thefuture will be less life-friendly. Heller’s feature story looks at how astronomersare searching for such worlds and what they may be like. Turn to page 32. Back on Earth, you can expect to see our Meta-Council on Emerging Tech-nologies 2015 list in late January, during the World Economic Forum’s meetingin Davos. And you don’t have to wait at all to dip into the rich knowledge resources in the UNESCO Library of Science: just point your browser to www.unesco.org/wls. A world of possibility awaits. BOARD OF ADVISERS Kaigham J. Gabriel Lawrence M. Krauss Robert E. Palazzo Michael Shermer Corporate Vice President, Director, Origins Initiative, Dean, University of Alabama at Publisher, Skeptic magazineLeslie C. Aiello Motorola Mobility, and Deputy, ATAP Arizona State University Birmingham College of Arts and Sciences President, Wenner-Gren Foundation Michael Snyder for Anthropological Research Harold “Skip” Garner Morten L. Kringelbach Carolyn Porco Professor of Genetics, Stanford Director, Medical Informatics and Director, Hedonia: TrygFonden Leader, Cassini Imaging Science University School of MedicineRoger Bingham Systems Division, and Professor, Virginia Research Group, University of Oxford Team, and Director, CICLOPS, Co-Founder and Director, Bioinformatics Institute, Virginia Tech and University of Aarhus Space Science Institute Michael E. Webber The Science Network Co-director, Clean Energy Incubator, Michael S. Gazzaniga Steven Kyle Vilayanur S. Ramachandran and Associate Professor,G. Steven Burrill Director, Sage Center for the Study of Mind, Professor of Applied Economics and Director, Center for Brain and Cognition, Department of Mechanical Engineering, CEO, Burrill Equities, LLC, University of California, Santa Barbara Management, Cornell University University of California, San Diego University of Texas at Austin and Burrill Media, LLC David J. Gross Robert S. Langer Lisa Randall Steven WeinbergArthur Caplan Professor of Physics and Permanent David H. Koch Institute Professor, Professor of Physics, Harvard University Director, Theory Research Group, Director, Division of Medical Ethics, Member, Kavli Institute for Theoretical Department of Chemical Department of Physics, Department of Population Health, Physics,University of California, Santa Engineering, M.I.T. Martin Rees University of Texas at Austin NYU Langone Medical Center Barbara (Nobel Prize in Physics, 2004) Astronomer Royal and Professor (Nobel Prize in Physics, 1979) Lawrence Lessig of Cosmology and Astrophysics,Vinton Cerf Lene Vestergaard Hau Professor, Harvard Law School Institute of Astronomy, University George M. Whitesides Chief Internet Evangelist, Google Mallinckrodt Professor of of Cambridge Professor of Chemistry and Physics and of Applied Physics, John P. Moore Chemical Biology, Harvard UniversityGeorge M. Church Harvard University Professor of Microbiology and John Reganold Director, Center for Computational Immunology, Weill Medical Regents Professor of Soil Science Nathan Wolfe Genetics, Harvard Medical School Danny Hillis College of Cornell University and Agroecology, Washington Director, Global Viral Forecasting Initiative Co-chairman, Applied Minds, LLC State UniversityRita Colwell M. Granger Morgan R. James Woolsey Distinguished University Professor, Daniel M. Kammen Professor and Head of Jeffrey D. Sachs Chairman, Foundation for the Defense University of Maryland College Park Class of 1935 Distinguished Professor Engineering and Public Policy, Director, The Earth Institute, of Democracies, and Venture Partner, and Johns Hopkins Bloomberg School of Energy, Energy and Resources Group, Carnegie Mellon University Columbia University Lux Capital Management of Public Health and Director, Renewable and Appropriate Energy Laboratory, University Miguel Nicolelis Eugenie C. Scott Anton ZeilingerRichard Dawkins of California, Berkeley Co-director, Center for Chair, Advisory Council, Professor of Quantum Optics, Founder and Board Chairman, Neuroengineering, Duke University National Center for Science Education Quantum Nanophysics, Quantum Richard Dawkins Foundation Vinod Khosla Information, University of ViennaDrew Endy Partner, Khosla Ventures Martin A. Nowak Terry Sejnowski Professor of Bioengineering, Director, Program for Evolutionary Professor and Laboratory Head Jonathan Zittrain Stanford University Christof Koch Dynamics, and Professor of Biology and of Computational Neurobiology Laboratory, Professor of Law and of ComputerEdward W. Felten CSO, Allen Institute for Brain Science of Mathematics, Harvard University Salk Institute for Biological Studies Science, Harvard University Director, Center for Information Technology Policy, Princeton University4 Scientific American, January 2015 Illustration by Ron Miller (cover image), Illustration by Nick Higgins (DiChristina) © 2014 Scientific American
[email protected] “If any life-form were uniquely human trait. Without motiva- special, it would be tion, our capacity for symbolic reasoning bacteria, which will would be of little use, and curiosity could be here long after the have provided it. human experiment is a distant memory.” Leon M. Rosenson via e-mail jeff schweitzer spicewood, tex. TATTERSALL REPLIES: Human “curiosi-September 2014 continue to evolve today. But Hawks does ty,” in the sense in which we understand not discuss the possible consequences of it today, is clearly enabled by our symbol-QUESTIONS OF LOGIC some of the evolutionary pressures that ic capacity to imagine that the worldThroughout the special issue on evolu- have been altered in the past century by could potentially be different from the onetion, a question based on a false premise medicine and public health. Could modern we immediately experience.is asked: What makes human special? As medical intervention inadvertently resulta minor branch on a vast evolutionary in the survival and spread of genetic muta- CONTRADICTORY VIEWS?bush, modern humans have been roam- tions that would otherwise have been elim- I am confused by the apparent contradic-ing the earth for no more than a few hun- inated or in the loss of protective genes? tion between statements in two articles.dreds of thousands of years—too littletime to demonstrate if the evolution of Martin J. Greenwood In his article, Tattersall writes that “alarge brains is a successful strategy for Stirling, Western Australia population needs to be small if it is to in-long-term survival of the species. If any corporate any substantial innovation, ge-life-form were special, it would be bacte- HAWKS REPLIES: A bit of thinking about netic or cultural. Large, dense populationsria, which will be here long after the hu- genetic drift and mutation shows that we simply have too much genetic inertia to beman experiment is a distant memory. need not worry about future generations nudged consistently in any direction.” But being “genetically weaker” because of in his article, Hawks asserts that “the huge Jeff Schweitzer medical technology and other modern ad- and rapidly increasing population size of Spicewood, Tex. vances. If selection is relaxed on a deleteri- our ancestors gave them many more rolls ous mutation, its frequency can change of the dice. As human populations have I find myself likening the attempt to only because of random genetic drift. Un- spread into new parts of the world andpinpoint where humanity began to pre- der drift alone, most rare mutations will grown larger, they have rapidly adapted toschoolers theorizing about candy they’ve become extinct over many generations. A their new homes precisely because thosefound scattered about a picnic area. A few may increase in frequency, but the populations were so big.”Hershey bar in the grass suggests choco- speed of genetic drift in a large populationlate grows there, whereas a Butterfinger is very slow. In our large populations, it Mel Tremperby the table surely fell out of a pocket. would take many thousands of genera- Berwyn Heights, Md. tions for any of today’s rare mutations to Inventing scenarios to try and fit ob- become common. THE EDITORS REPLY: Although Tatter-servations are where theories come from. sall’s and Hawks’s statements might ap-Still, beware that in our eagerness to ex- I look with wonder and joy on people pear contradictory, they actually refer toplain, we risk elevating accidents of the today living happy lives by managing different evolutionary scenarios.discovery process to primary evidence. once fatal genetic disorders. If we can ad- vance medical technology and public Tattersall’s article focuses on evolution David K. Elliott health in ways that release people from in small populations of early human an- Oxford, Mass. such lethal disorders for the next few cestors that were isolated from one anoth- thousand generations, I think we have er and lived in different environments.MODERN EVOLUTION little to fear from genetic drift. Under such conditions, random geneticAs John Hawks states in “Still Evolving (Af- and cultural changes (both beneficial andter All These Years),” human populations CURIOUS CREATURE neutral) could have accumulated rapidly, In “If I Had a Hammer,” Ian Tattersall thereby leading such populations to dif- cites our capacity for symbolic reasoning ferentiate and, ultimately, speciate. as one of the traits unique to humans that led to the rise of our species’ dominant In contrast, Hawks’s article focuses position on the earth. I believe that our specifically on adaptive genetic changes highly developed curiosity is another key, within large populations of Homo sapi- ens. Large populations have more mat- ings and hence more chances for beneficial genetic changes to arise, thus facilitating adaptation to the novel environments our species encountered as it spread out from Africa across the world.6 Scientific American, January 2015 © 2014 Scientific American
LettersSEX AND THE EXPERIMENT ESTABLISHED 1845 LETTERS TO THE EDITORIn criticizing the National Institutes of EDITOR IN CHIEF AND SENIOR VICE PRESIDENT Scientific AmericanHealth’s new policy requiring the scien-tists it funds to use equal numbers of male Mariette DiChristina 75 Varick Street, 9th Floorand female animal subjects in their re- New York, NY 10013-1917search [“Vive la Différence,” Forum], R. EXECUTIVE EDITOR DESIGN DIRECTOR or [email protected] Fields claims that doing so wouldcreate problems because it would increase Fred Guterl Michael Mrak Letters may be edited for length and clarity. >[email protected] phase, one might have a “two-by-two CONTRIBUTING EDITORS For single copies of back issues: 800-333-1199.design” (experimental group versus con- Permissionstrol group and male versus female). Davide Castelvecchi, Katherine Harmon Courage, For permission to copy or reuse material: Anna Kuchment, Maryn McKenna, George Musser, Permissions Department, David Lopez-Lee Scientific American, 75 Varick Street, Professor Emeritus Christie Nicholson, John Rennie, Sarah Simpson 9th Floor, New York, NY 10013-1917; University of Southern California [email protected]; CONTRIBUTING WRITER www.ScientificAmerican.com/permissions. Please allow three to six weeks for processing. Ferris Jabr Advertising ART DIRECTOR Jason Mischka www.ScientificAmerican.com has ART DIRECTOR, INFORMATION GRAPHICS Jen Christiansen electronic contact information for sales ART DIRECTOR, ONLINE Ryan Reid representatives of Scientific American in PHOTOGRAPHY EDITOR Monica Bradley all regions of the U.S. and in other countries. PHOTO RESEARCHER Liz Tormes ASSOCIATE ART DIRECTOR, IPAD Jason Arias Scientific American is a trademark of ASSISTANT ART DIRECTOR, IPAD Bernard Lee Scientific American, Inc., used with permission. MANAGING PRODUCTION EDITOR Richard Hunt SENIOR PRODUCTION EDITOR Michelle Wright INFORMATION GRAPHICS CONSULTANT Bryan Christie ART CONTRIBUTORS Edward Bell, Lawrence R. Gendron, Nick Higgins COPY DIRECTOR Maria-Christina Keller SENIOR COPY EDITORS Michael Battaglia, Daniel C. Schlenoff COPY EDITOR Aaron Shattuck SENIOR EDITORIAL PRODUCT MANAGER Angela Cesaro PRODUCT MANAGER Kerrissa Lynch WEB PRODUCTION ASSOCIATE Nick Bisceglia EDITORIAL ADMINISTRATOR Avonelle Wing SENIOR SECRETARY Maya Harty SENIOR PRODUCTION MANAGER Christina Hippeli ADVERTISING PRODUCTION MANAGER Carl Cherebin PREPRESS AND QUALITY MANAGER Silvia De Santis CUSTOM PUBLISHING MANAGER Madelyn Keyes-Milch PRODUCTION COORDINATOR Lisa HeadleyFIELDS REPLIES: The essence of experi- PRESIDENTmental research is careful discrimination.Comparing similar groups enables more Steven Inchcoombediscerning distinctions. There is no magicstatistical method that can overcome the EXECUTIVE VICE PRESIDENT SALES DEVELOPMENT MANAGERrealities that variances add: increasingthe number of categories from two to four Michael Florek David Tirpackmakes it more difficult to draw conclu-sions without increasing the sample size. VICE PRESIDENT AND PROMOTION MANAGER ASSOCIATE PUBLISHER, MARKETING The scientific method uses deductive Diane Schubereasoning to reject a specific hypothesis. AND BUSINESS DEVELOPMENTUnlike Whissell’s assertion, it does not per- PROMOTION ART DIRECTORmit any generalization. Further, only a Michael Vosssmall fraction of NIH grant applications Maria Cruz-Lordare funded. The mandate imposes a specific DIRECTOR, INTEGRATED MEDIA SALEShypothesis to test in every grant and cir- MARKETING RESEARCH DIRECTORcumvents the normal peer review that con- Stan Schmidtsiders whether testing a hypothesis in each Rick Simonecase is, for instance, prudent or practical. ASSOCIATE VICE PRESIDENT, BUSINESS DEVELOPMENT ONLINE MARKETING PRODUCT MANAGER Diane McGarvey Zoya Lysak VICE PRESIDENT, GLOBAL MEDIA ALLIANCES CORPORATE PR MANAGER Jeremy A. Abbate Rachel Scheer VICE PRESIDENT, CONSUMER MARKETING SENIOR INTEGRATED SALES MANAGER Christian Dorbandt Jay Berfas DIRECTOR, INTERNATIONAL SALES REPRESENTATIVE DIGITAL DEVELOPMENT Chantel Arroyo Richard Zinken SENIOR ADMINISTRATOR, ASSOCIATE CONSUMER EXECUTIVE SERVICES MARKETING DIRECTOR May Jung Catherine Bussey CUSTOM PUBLISHING EDITOR E-COMMERCE MARKETING MANAGER Lisa Pallatroni Evelyn Veras RIGHTS AND PERMISSIONS MANAGER MARKETING AND CUSTOMER SERVICE COORDINATOR Karin M. Tucker Christine Kaelin8 Scientific American, January 2015 © 2014 Scientific American
Science Agenda by the EditorsOpinion and analysis from Scientific American’s Board of EditorsA Hacker’s Guide governments of Germany and India, eventually stopped pursu- ing the idea after an international treaty against ocean dump-to Planet Cooling ing added cautions about such experiments.“Geoengineering” our climate We need to get over the environmentalist skittishness thatsounds like an idea from the mind thwarts these small tests of climate manipulation. Civilizationof Dr. Strangelove, but tests of the may depend on such geoengineering methods as the planetmethods may save us from disaster keeps warming. We need tests to get them right—and stop peo- ple from doing them wrong.In 2009 biological oceanographer Victor Smetacek tried to sinkour global warming problem in the sea. The researcher, his sci- Humanity is on pace to raise the planet’s thermostat by fourentific team and the crew of the ship RV Polarstern sailed to the degrees Celsius by 2100, according to the IntergovernmentalSouthern Ocean and poured a solution of iron into a small eddy. Panel on Climate Change. Its latest report states that technolo-Iron, a nutrient, triggered a phytoplankton bloom, and the tiny gy to pull CO2 from the air will be needed to avoid that rise.photosynthesizers sucked carbon dioxide from the sky as theygrew. When the plankton died, they drifted like snow to the bot- There are at least two families of geoengineering ideas: thosetom of the ocean, entombing CO2 in their tiny corpses. that get rid of CO2, the primary greenhouse gas, and those that seek to block sunlight, which buys time. Scientists and engi- Although the technique, if used widely, could bury a billion neers have proposed various approaches besides iron fertiliza-metric tons of this greenhouse gas every year, the experiment tion, such as hazing the skies with sulfates to mimic the coolingdrew the ire of environmentalists. Such iron fertilization was effects of a volcanic eruption or even launching a fleet of mir-condemned by organizations such as the World Wide Fund for rors to deflect sunlight away from the planet. The problem withNature and the ETC Group, some other scientists, and Germa- any of these approaches is that scientists do not know muchny’s environment minister, who worried about unforeseen and about potential side effects. Could plants genetically eng ineeredtoxic side effects, such as plankton growth harming the food for supercharged photosynthesis kick off another Ice Age bychain. Smetacek, who had received prior approval from the drawing down too much CO2? Would artificial volcanoes shut off crucial Asian monsoon rains by altering cloud and wind pat- terns? Would any of these world-changing ideas work in the first place, and are some too crazy to pursue? The only way to find out for sure is to do what Smetacek did: test them, in a contained, rigorous, transparent manner. Not only did the oceanographer obtain government permission, he published the findings and data in a scientific journal so all could see. Yet even small tests like this are taboo. When U.K. res earchers announced plans to spray a few tubs of water into the sky in 2011, more than 70 organizations from around the world signed a protest petition. The scientists backed off. These attitudes need to change, and scientific funding agencies need to support such research. The small but discernible effects of a restricted test should do no long-lasting damage. Smetacek’s plankton bloom faded quickly. The eruption of Mount Pinatubo in 1991— a large-scale geoengineering “experiment”—did not have lasting climate effects. Geoengineering experiments do carry risks: setting off arti- ficial volcanoes all over the globe, for instance, might destroy the ozone layer. That is another reason why geoengineering conc epts need testing: so people know what not to do. After all, Smetacek and his crew are not the only people to try out iron fertilization. In 2012 independent entrepreneur Russ George dumped iron overboard with the idea of restoring salmon fisheries and selling carbon credits. That is the kind of rogue geoengineering that we cannot afford. SCIENTIFIC AMERICAN ONLINE Comment on this article at ScientificAmerican.com/jan201510 Scientific American, January 2015 Illustration by Morgan Schweitzer © 2014 Scientific American
Forum by Carl Benedikt Frey Carl Benedikt Frey is a research fellow of the Oxford Martin School at the University of Oxford and a member of the deCommentary on science in the news from the experts partment of economic history at Lund University in Sweden. He is also a specialist adviser to the Digital Skills Committee at the House of Lords of the U.K. Parliament.The End of Economic Growth?How the digital economy could lead to secular stagnationLast September e-commerce giant Amazon acquired Twitch, a wrote that “when a revolutionary new industry . . . reaches matu-live-streaming video company, for $970 million. Not long ago rity and ceases to grow, as all industries finally must, the wholea new billion-dollar company would have been a boon to job economy must experience a profound stagnation. . . . And whencreation. Yet Twitch employs just 170 workers. giant new industries have spent their force, it may take a long time before something else of equal magnitude emerges.” With- The story of Twitch illustrates an important lesson about the out new job-creating industries to take the place of those thatdigital economy: at the same time it has generated enormous came before, the economy might stagnate.wealth for shareholders and entrepreneurs, it has resulted in fewnew jobs. In fact, the digitization of the economy may have far- The problem is that most industries formed since 2000—elec-reaching implications for the future of growth and employment. tronic auctions, Internet news publishers, social-networking sites, and video- and audio-streaming services, all of which appeared in In a series of recent articles on the state of the digital economy, official industry classifications for the first time in 2010—employformer U.S. treasury secretary Lawrence Summers revived the far fewer people than earlier computer-based industries. Where-notion of secular stagnation, an idea first presented by economist as in 2013 IBM and Dell employed 431,212 and 108,800 workers,Alvin Hansen during the Great Depression. Hansen’s theory sug- respectively, Facebook employed only 8,348 as of last September.gested that as population growth slows and the rate of capital-absorbing innovation (that is, investment opportunities created The reason these businesses spin off so few jobs is that theyby the arrival of new technologies) tapers off, investment will fall, require so little capital to get started. According to a recent surveyleading to slower economic growth and fewer new jobs. of 96 mobile app developers, for example, the average cost to develop an app was $6,453. Instant-messaging software firm During the growth miracle of the postwar period, Hansen’s WhatsApp started with a relatively meager $250,000; it emp loyedtheory proved spectacularly wrong. Technological advances dur- just 55 workers at the time Facebook announced it was buying theing the 1930s and the increase in capital investment associated company for $19 billion. All of which explains why new technolo-with World War II did enough to stave off stagnation. After that, gies throughout the 2000s have brought forth so few new jobs.the baby boomer generation entered the workforce, pushing the According to my own research with Thor Berger of Lund Universi-economy ahead. Then, in the 1980s and 1990s, investment in com- ty in Sweden, in 2010 only about 0.5 percent of the U.S. workforceputer and information-processing equipment surged, facilitating was employed in industries that did not exist a decade earlier.a wide range of entirely new computer-related occupations. Summers is likely to be proved right as digital technologies But after 2000, when the first wave of IT investment peaked, lead to insufficient investment and growing inequality reducesthe demand for new work in the U.S. declined. Hansen famously spending. Yet there is much that governments can do to prevent stagnation. They can redistribute income to those with a higher propensity to spend. They can also support investment into indus- tries that might foster more new jobs than digital technologies— jobs for solar photovoltaic installers, wind energy engineers, bio- fuels production managers and transportation planners. Finally, while digital technologies may create fewer jobs than previous innovations, they also substantially reduce the amount of money it takes to start a new digital business—and that will make it possible for more people to become entrepreneurs. In deed, self-employment might become the new normal. The chal- lenge for economic policy is to create an environment that re wards and encourages more entrepreneurial risk taking. A basic guaranteed income, for instance, would help by capping the downside to entrepreneurial failure while boosting spending and combating inequality. SCIENTIFIC AMERICAN ONLINE Comment on this article at ScientificAmerican.com/jan201512 Scientific American, January 2015 Illustration by Nick Ogonosky © 2014 Scientific American
ADVANCES Dispatches from the frontiers of science, technology and medicine Asteroids could be stepping-stones for human expansion into the solar system. A E R O S PA C E Dancing with the Asteroids NASA’s proposed human mission to a space rock has a bumpy road aheadCOURTESY OF NASA AND JPL/CALTECH The Obama administration wants to yet to be built, but the parties involved rendezvous procedures and establish pro- send humans to Mars in the 2030s. Of hope to have the rock relocated to the tocols for sample collection and extrave- course, such a mission requires a lot of moon’s vicinity as soon as 2021. nasa calls hicular movements. And it would do all advance engineering, and as a first step, this concept the Asteroid Redirect Mis- of this while keeping astronauts relatively nasa plans to send astronauts to a small sion (ARM) and is marshaling resources safe, staying sufficiently close to home so asteroid that would be brought into a sta- across the entire agency to support it. that if something went wrong, the crew ble orbit around the moon. To achieve could potentially make an emergency that mechanical feat, a solar-powered Michele Gates, the agency’s program return to Earth. robotic probe is being designed to cap- director for ARM, says that its advanced ture a space rock and slowly push it into propulsion technology and crew activities ARM’s critics are loud and legion, how- place. A target asteroid has yet to be an would give nasa the capability and expe- ever. In June the prestigious National Re nounced, and the robotic space tug has rience needed to someday reach Mars. search Council issued a report stating that The trip would demonstrate spacecraft the mission could divert U.S. res ources FURTHER READINGS AND CITATIONS S cientificAmerican.com/jan2015/advances January 2015, ScientificAmerican.com 13 © 2014 Scientific American
ADVANC E S and attention from more worthy space look for more asteroids before it leaps exploration, highlighting parts of ARM as into ARM. A robust asteroid survey, he dead ends on the path to Mars. The harsh- says, would discover suitable targets for a est criticisms have come from asteroid sci- crewed mission that would not require an entists. Mark Sykes, director of the Plane- expensive orbital relocation. “By the time tary Science Institute in Tucson, Ariz., we would tow a tiny rock into lunar orbit, ridiculed ARM last September while testi- we could be discovering more attractive, fying to a congressional committee, saying larger objects passing through the Earth- that the agency’s tentative cost estimate of moon system that are easy to reach,” less than $1.25 billion for the concept’s Binzel notes. robotic component strained credulity. nasa plans to conduct a formal review “It doesn’t advance anything,” Sykes of the ARM concept in February, and the says, “and everything that could benefit Obama administration’s next budget pro- from it could be benefited far more by posal is expected to request more funding other, cheaper, more efficient means.” for ARM. But the redirect’s fate may have already been sealed by 2014’s midterm The mission’s detractors miss the elections, in which Republicans, who are point that it represents the nation’s best largely opposed to the mission, took full opportunity in the foreseeable future to control of Congress. With this latest blow maintain its momentum in human space- to nasa’s post–Space Shuttle plans for flight, says Louis Friedman, a space policy human spaceflight, the agency’s astro- expert who helped to conceive ARM. nauts may end up boldly going nowhere for many years to come—reg ardless of To this point, planetary scientist Rich- the approach. —Lee Billings ard Binzel of the Massachusetts Institute of Technology argues that nasa needs to TECHNOLOGY Oscillating weight The Pulse of Pacemakers Rectifier and spring An automatic wrist- watch mechanism Generator harnesses heartbeats Electronic pacemakers time the heartbeats of more ing parts, enclosed the winding mechanism in a three- than three million people in the U.S. For these pa centimeter-wide case and sutured it to a live pig’s tients, surgery is a regular occurrence. A pacemak heart.The prototype produced 50 microwatts of er’s batteries must be swapped out every five to power; pacemakers need about 10. eight years, and the electric leads that connect the device to the heart can wear out, too. The device currently has a“messy setup,”says Adrian Zurbuchen, who presented details about it at In an effort to eliminate the batteries and leads the European Society of Cardiology Congress late last altogether, biomedical engineers at the University of summer. Wires connect the watch parts to a box con Bern in Switzerland have built a heartbeat-powered taining electronics and a pacemaker. The goal is to pacemaker, assembled from self-winding clockwork have everything in one device. It will not be ready for technology that is more than two centuries old. prime time soon, predicts Spencer Rosero, who is director of the pacemaker clinic at the University of Automatic wristwatches, invented in 1777, con Rochester Medical Center and was not involved in the tain a weighted rotor that turns when a wearer’s project. He says if tests are successful, medicine will wrist moves. The rotor winds up a spring, and when most likely first see a pacemaker with both a battery the fully coiled spring unwinds, it turns the watch’s and energy-harvesting components. —Prachi Patel gears. In modern versions, the gears drive a tiny current-producing generator. Like the jostling of a wrist, a beating heart can also wind a spring, the Swiss team found.The researchers stripped an automatic wristwatch of its time-indicat14 Scientific American, January 2015 Graphic by Brown Bird Design © 2014 Scientific American
BIOLOGYBacteria?They LoveAll ManureCow dung encouragesantibiotic resistance,even if it comes fromdrug-free cowsWhen antibiotics first became avail- The cow-pieable, farmers used them indiscriminately— results suggestdribbling streptomycin into chicken feed to there are moreboost growth and doling out low doses to factors promotingfatten pigs. Now scientists know that the resistance besidesoveruse of antibiotics in livestock can foster antibiotic use.drug-resistant bacteria that are dangerousto human health. Amid debates over what manure from pigs treated with antibioticskinds of restrictions should be put in place, contains resistant bacteria, including Esche-figuring out how antibiotic-resistant bacte- richia coli, but the cow-pie results suggestria evolve and make their way to humans there are more factors promoting resis-remains an area of intense interest. tance besides antibiotic use. Something about manure itself may encourage natu- Jo Handelsman is tracing one such rally resistant bacteria to proliferate.pathway that, as she puts it, travels from“barn to table.” Handelsman, a microbiolo- The findings should not, however, givegist who is now associate director for sci- the perception that resistance is every-ence at the White House Office of Science where, notes Lance Price, a microbiologistand Technology Policy, looked into dairy at George Washington University (whocows, which are often treated with antibiot- was not involved in the study). Widespreadics and produce manure that farmers use resistance is not inevitable, he says. “Weon their crops. In addition to nutrients, that can control this. There’s very clear evidencefragrant fertilizer may harbor antibiotic- that when we turn off the antibiotic spigot,resistant bacteria—a problem because the we bring down drug-resistant bacteria.”microbes can come into contact with plantsthat are subsequently shipped to supermar- Next on the farm-to-table agenda,kets and sometimes eaten raw. Handelsman will test whether radishes grown in soil treated with cow manure are To tease out how those antibiotic-resis- capable of taking up resistant genes fromtant bacteria come to exist, Handelsman bacteria via their vascular system. “Theyand her colleagues at Yale University added have veins just like us,” she says. “We don’tmanure from a nearby Connecticut farm to have any evidence yet that they’re takingraised beds of soil in 2013. In this case, the up the bacteria, but it’s a really interestingmanure specifically came from cows that possibility.” —Peter Andrey Smithwere not treated with antibiotics. Theresearchers unexpectedly found that soilbacteria carrying antibiotic-resistant genesbecame more abundant when they weregrown with the manure than when theywere grown with synthetic nitrogen-basedfertilizer—even though the cows weredrug-free. The team published its work inOctober in the Proceedings of the NationalAcademy of Sciences USA. Previous research has found thatIllustrations by Thomas Fuchs January 2015, ScientificAmerican.com 15 © 2014 Scientific American
ADVANC E S Light-sensitive tubes amplify anti neutrino signals at Daya Bay in China. PHYSICS Theoretical Particles, Still Theoretical No signs of the rumored “sterile” neutrino Neutrinos come in three types, or flavors: electron, muon and tau. But physicists sus pect that others may be out there and that they will be weird—almost never interacting with other particles. These “sterile” neutrinos may resolve some of physics’ biggest mysteries. For example, they could contribute to the befuddling dark matter that ap parently pervades the universe and exerts a gravitational pull on regular matter. Despite decades of looking, however, sterile neutrinos remain elusive, and the latest attempt to catch them in action recently turned up empty, too. Physicists running the international Daya Bay Reactor Neutrino Experiment in China, which studies neutrino behavior, found no evidence for sterile neutrinos after a seven-month-long hunt. This particular search took place underground: Daya Bay’s neutrino detectors are buried at various depths below a group of nuclear power reactors in the province of Guangdong. That is because the fission reactions that take place at the plant naturally produce lots of the antimatter counterparts of electron-flavored neutrinos. Neutrinos, strangely enough, can switch flavors in a process called oscillation, so as these antimatter particles go flying, some of them change into muon or tau antineutrinos, COURTESY OF ROY KALTSCHMIDT Lawrence Berkeley National Laboratory hitting the detectors along the way. Scientists know roughly how many of the electron antineutrinos should change into the other flavors, and they use this calculation to figure out if any electron antineutrinos are missing at the deepest detectors. Missing particles would mean the originals probably turned into sterile neutrinos. The absence of missing neutrinos at Daya Bay “leaves no room open in this particular territory for having a sterile neutrino,” says Brookhaven National Labora tory physicist Milind Diwan, a member of the experiment’s team. The results, pub lished in October in Physical Review Letters, rule out the particles only in a certain range of masses and characteristics, however, so the ultimate truth about sterile neutrinos is still out there. Physicists at the site will continue looking for the particles within a broader range of characteristics. After all, the first 30 years’ worth of searches for the Higgs boson turned up nothing. —Clara Moskowitz16 Scientific American, January 2015 COMMENT AT S cientificAmerican.com/jan2015 © 2014 Scientific American
C O N S E R VAT I O N Monikers Matter An animal’s name could determine its fate If all goes according to plan, cement and concrete maker Lafarge will continue turning a limestone hill in Malaysia into a quarry. It would be business as usual for Lafarge, but bad news for Charopa lafargei, a recently discovered snail that lives only on that hill. The gastropod’s name is no coincidence. For the first time, taxonomists have named a species after the entity that could cause the creature’s extinction. Whether this guilt trip will work remains to be seen (Lafarge has said it will avoid WHAT’S IN certain areas of the A NAME? hill), but there isSOURCE: “WHAT’S IN A NAME? DO SPECIES’ NAMES IMPACT STUDENT SUPPORT FOR CONSERVATION?” BY PAUL T. KARAFFA, Survey respondents something to be M. M. DRAHEIM AND E.C.M. PARSONS, IN HUMAN DIMENSIONS OF WILDLIFE: AN INTERNATIONAL JOURNAL, VOL. 17, NO. 4; 2012 deemed an animal said for choosing with a positive the name of a name (green) more species carefully. conservation-worthy Research has shown than its negatively that an animal’s named self (red). common name can affect whether RATING people want to ( percent)* protect it. In a 2012 study, George Patriot falcon 68 Mason University Killer falcon 53 American eagle 77 researchers found Sheep-eating eagle 46 that species with patriotic or cute Great American wolf 66 names are more Eastern coywolf 48 likely to inspire American otter† 68 public support for Hairy-nosed otter† 41 their conservation. The team that Furry-nosed otter† 63 described the snail Sharp-clawed otter† 34 hopes that the same *P ercent of study participants who wanted to principle will help conserve the animal. All names are fictional. persuade Lafarge to †F rom an unpublished follow-up study by protect C. lafargei. Caitlyn Scott and Chris Parsons of George —David Shiffman Mason University. January 2015, ScientificAmerican.com 17 © 2014 Scientific American
ADVANC E SPSYCHOLOGY to become soned manner in comparison to the kids “less friendly without controlling parents. And when theyParental [when] I did did speak up, they often failed to expressControls not see things themselves in warm and productive ways. her way.”Pushy parents could The research- The researchers suspect that manipula-harm kids’ social skills ers followed up tive parents undermine their child’s ability with the subjects at to learn how to argue his or her own view-As countless unmade beds and ages 18 and 21, asking point in other relationships. Although par-unfinished homework assignments attest, the young adults to bring along ents do need to set boundaries, domineer-kids need rules. Yet how parents make a close friend and, later, a romantic partner ing tactics imply that any disagreement willdemands can powerfully influence a child’s if they had one. These pairs were asked to damage the bond itself. Separate findingssocial skills, psychologists at the University answer hypothetical questions that were suggest that parents who explain the rea-of Virginia recently found after the conclu- purposefully written to provoke a difference sons behind their rules and turn disagree-sion of a study investigating the notorious of opinion. “We wanted to see whether ments into conversations leave youngsterstransition from adolescence to adulthood. they could navigate a disagreement in a better prepared for future disputes. healthy way,” says study leader Barbara Initially 184 13-year-olds filled out mul- Oudekerk, now at the U.S. Department of The consequences of tense or domi-tiple surveys, including one to assess how Justice’s bureau of statistics. neering relationships appear to compoundoften their parents employed psychologi- In the October issue of Child Develop- with time. This study also found that socialcally controlling tactics, such as inducing ment, Oudekerk and her colleagues report difficulties at 18 predicted even poorerguilt or threatening to withdraw affection. that the 13-year-olds who had highly con- communication abilities at age 21. Psychol-The kids rated, for example, how typical trolling parents floundered in friendly dis- ogist Shmuel Shulman of Bar-Ilan Universi-it would be for Dad to suggest that “if I agreements at age 18. They had difficulty ty in Israel, who did not participate in thereally cared for him, I would not do things asserting their opinions in a confident, rea- work, thinks these conclusions convincinglythat caused him to worry” or for Mom reveal how relationship patterns “carry for- ward” into new friendships. —Daisy Yuhas18 Scientific American, January 2015 COMMENT AT S cientificAmerican.com/jan2015 © 2014 Scientific American
H E A LT H EBOLA SUITS WHERE Approximately THEY 12,500 Ebola virus ARE capsules can fit MADE side by side through a hole the size of a pinprick in a piece of clothing, and because exposure to just a few of the capsules can cause infection, protective barriers are a must for those who come into contact with patients. Lakeland Industries, a global manufacturer of protective clothing based in Ronkonkoma, N.Y., is one of a few companies that sews the plastic ChemMAX and MicroMAX suits that health care workers wear as shields. As a result of the recent Ebola outbreak, Lakeland estimates that it received orders for about one million suits between late Sep- tember and early November— a number that does not include requests for hoods, foot coverings and gloves. To accommodate the demand, its primary factory in Shandong Province, China (above), has hired more employees andJOHANNES EISELE Getty Images invested in new machinery. By January the company expects its typical monthly production will have doubled. —Julia Calderone January 2015, ScientificAmerican.com 19 © 2014 Scientific American
Brown bears hibernate for as long as eight months. PHYSIOLOGY grizzly bears gain 100 pounds or more each ALAMY autumn and somehow avoid diabetes. A Health Advice recent study found that the grizzlies’ fat cells from a Grizzly become more sensitive to insulin as they prepare for the winter, allowing the bears to What humans can learn keep processing and storing sugar. Scientists from animals that sleep at biotechnology company Amgen are now for months on end testing whether tweaking the same protein that controls sensitivity in diabetic humans Hibernation is a complex solution to a could have similar results. simple problem. In winter, food is scarce. To survive this seasonal famine, animals, THREAT: Osteoporosis such as the arctic ground squirrel and black INSIGHT: If a human were to lie still for long bear, induce a sedentary state under which periods without food, his or her bones physiological shifts keep them alive despite would slowly degrade. A black bear, howev the lack of food, water and movement. er, emerges from its den after winter just as Researchers and doctors alike are interested strong as ever because its bone is recycled at in how these hibernation tricks could help 25 percent of normal levels during hiberna humans with their own health. tion. Researchers at Colorado State Universi —Amy Nordrum ty are now trying to identify the hormones that control this extreme limit on bone turn THREAT: Stroke over. They aim to create a drug for people at INSIGHT: B lood flow in the brain of a hiber risk for osteoporosis that similarly protects nating arctic ground squirrel drops to a tenth bone density. of normal. Typically such oxygen deprivation would cause a stroke. But these squirrels can THREAT: Heart Disease survive all winter because their metabolism INSIGHT: During cardiac surgery, a patient lowers to 2 percent of its summer rate—re becomes oxygen-deprived when the heart quiring much less oxygen to maintain. If stops beating. To cope, the body switches paramedics could similarly lower the metab from aerobic to anaerobic metabolism. olism of a human patient immediately after Unfortunately, the change creates lactic a stroke—perhaps by cooling the body— acid, which can kill cells if it builds up. Dam they might prevent permanent brain dam age of this kind does not occur in hibernat age, says Brian Barnes, a biologist at the ing arctic ground squirrels, likely because University of Alaska Fairbanks. they break down more fats than sugars even after the heart has slowed to just one beat THREAT: Diabetes per minute. Collaborating researchers at INSIGHT: People who gain a lot of weight Duke University and the University of Alaska often stop responding to insulin. The hor Fairbanks are now working to identify how mone regulates the amount of glucose that this species prioritizes fat as fuel in low-oxy cells take up from the blood; too much sugar gen conditions. Finding a way to coax cardi in the blood results in type 2 diabetes. Yet ac surgery patients to do the same may reduce injury to organs during procedures. 20 Scientific American, January 2015 COMMENT AT ScientificAmerican.com/jan2015 © 2014 Scientific American
ADVANC E SIN THE NEWS SCOTLAND SWEDEN Police officers began enforcing a new blood alcohol limit Örnsköldsvik is set toQuick Hits for drivers in December. The legal maximum dropped become the world’s first from 0.8 to 0.5 milligram per milliliter—essentially remotely controlled airport.U.S. a zero-tolerance policy that rules out even a single glass Air-traffic controllers areT wo leading groups of of wine for those planning to get behind the wheel. testing a system of camerasphysicians now recommend and sensors that replaceshormonal implants and humans and issues comintrauterine devices (IUDs) mands across multipleas first-line birth control airports at once.for teen girls. These long-acting methods have a ITALY INDIAhigher success rate than T he military will start growing marijuana this year in an The government introduceddaily birth-control pills. effort to make prices competitive with imported supplies. its first national mental The country legalized marijuana for medicinal use in 2013. health policy as part of a plan VATICAN CITY to increase access to re The Sistine Chapel installed 7,000 LEDs to sources for psychological illuminate the ceilings where Michelangelo’s well-being. With a suicide masterpieces are painted. Sunlight and rate that is double the global halogen bulbs were fading the frescoes. average, India currently has only about 3,500 For more details, visit www.ScientificAmerican.com/jan2015/advances psychiatrists for its 1.2 billion citizens. January 2015, ScientificAmerican.com 21 © 2014 Scientific American
The Science of Health The Best Gene Screen ings that required further testing or decisions about treatment. SOURCE: “ACMG RECOMMENDATIONS FOR REPORTING OF INCIDENTAL FINDINGS IN CLINICAL EXOME AND GENOME SEQUENCING,” BY ROBERT C. GREEN ET AL., IN GENETICS IN MEDICINE, VOL. 15, NO. 7; JULY 2013 Separately, Christine Eng, medical director of the DNA Diag Information about most rare genetic mutations is so uncertain as to be meaningless. As a result, geneticists nostic Laboratory at the Baylor College of Medicine, says her recommend testing only for genes that clearly increase team has conducted more than 2,000 whole exome tests since the risk of developing certain conditions. A list of these October 2011 with about 95 incidental findings. “That’s an inci ailments and their associated genes appears below. dence of about 5 percent,” she notes. Most of the findings did not require immediate action. Usually they prompt more frequent CANCERS AND PRECANCEROUS CONDITIONS screening tests, often for breast cancer or colorectal cancer. ■■ Familial adenomatous polyposis—APC ■■ Familial medullary thyroid cancer—RET BALANCING ACT ■■ Hereditary breast and ovarian cancer—BRCA1, BRCA2 In the hope of minimizing the number of people forced to cope ■■ Li-Fraumeni syndrome—TP53 with incidental findings, the American College of Medical Genet ■■ Lynch syndrome—MLH1, MSH2, MSH6, PMS2 ics and Genomics (ACMG) in 2013 proposed regularly returning ■■ Multiple endocrine neoplasia type 1—MEN1 results on 56 genes from comprehensive genetic tests. The pro ■■ Multiple endocrine neoplasia type 2—RET fessional group felt that there was enough—though by no means ■■ MYH-associated polyposis and related conditions—MUTYH conclusive—information about these specific mutations to merit ■■ Peutz-Jeghers syndrome—STK11 letting patients know if they had tested positive for them. In other ■■ PTEN hamartoma tumor syndrome—PTEN words, the mutations “met a standard of relatively high likeli ■■ Retinoblastoma—RB1 hood of being disease-causing.” The list included genetic vari ■■ Von Hippel–Lindau syndrome—VHL ants that have been strongly linked to retinoblastoma (cancer of ■■ WT1-related Wilms tumor—WT1 the eye), hereditary breast cancer and long QT syndrome. The ACMG believed that its guidance would give physicians a short HEART AND VASCULAR DISORDERS cut so they would not need to haphazardly guess which muta ■■ A rrhythmogenic right ventricular cardiomyopathy—PKP2, tions had a strong enough link to a given malady to tell patients about the results. DSP, DSC2, TMEM43, DSG2 ■■ C ertain other cardiomyopathies—MYBPC3, MYH7, TNNT2, Such advice is particularly important given how often chil dren undergo genetic tests nowadays. “About 80 percent of our TNNI3, TPM1, MYL3, ACTC1, PRKAG2, GLA, MYL2, LMNA cases are pediatric-aged, so the incidental findings are being ■■ C atecholaminergic polymorphic ventricular found in the children, and many of the conditions are adult- onset conditions,” Eng says. Families given such information tachycardia—RYR2 about their children then may have to wait decades before they ■■ Ehlers-Danlos syndrome (vascular type)—COL3A1 can do anything about it or decide when, if ever, to start consid ■■ L ong QT syndromes and Brugada syndrome—KCNQ1, ering treatment for a disorder that may not ever develop. KCNH2, SCN5A Yet a year after issuing its guidance, the ACMG produced an ■■ M arfan syndrome and related conditions—FBN1, TGFBR1, addendum: patients should have the opportunity to opt out of having information about even that short list of analyzed TGFBR2, SMAD3, ACTA2, MYLK, MYH11 genes. “When families are given a choice, a very large percent age of them want this information, but there are some individ NONCANCEROUS GROWTHS uals who feel they do not want this information, so I think this ■■ Hereditary paraganglioma-pheochromocytoma syndrome— option is a good one,” says Eng, who was not on that decision- making board. SDHD, SDHAF2, SDHC, SDHB ■■ Neurofibromatosis type 2—NF2 For her part, Murphy is still grappling with how to respond ■■ Tuberous sclerosis complex—TSC1, TSC2 to her incidental finding. She is not yet 30, and she finds it hard to imagine being young and carefree and on beta blockers. OTHER “Generally, I’m a very healthy person. I was doing just fine until ■■ Familial hypercholesterolemia—LDLR, APOB, PCSK9 now, so why does it matter that I found this out?” she asks. “I’ve ■■ Malignant hyperthermia susceptibility—RYR1, CACNA1S been giving it a lot of thought, and if I hadn’t gotten [the test] done, I might never have known about this. Now I’m wonderingshare with patients and for how best to help them deal with the if I really want a lifestyle change. It’s a lot to think about.” Yetinevitable incidental findings. the hope is that Murphy’s experience, and those of other pa tients, will help geneticists decide which tests to include in fu Before making any definitive recommendations, however, ture gene scans and better prepare patients and health carethey need to know how often genetic results produce such find workers for dealing with any unwelcome surprises. ings. To that end, Evans is heading up the NCGENES clinicaltrial, part of a larger effort by three organizations, including SCIENTIFIC AMERICAN ONLINEthe University of North Carolina School of Medicine. Of the Comment on this article at ScientificAmerican.com/jan2015roughly 300 patients who have received genetic informationsince Evans started ordering whole exome tests a couple ofyears ago, he says, six of them (or 2 percent) had incidental find30 Scientific American, January 2015 © 2014 Scientific American
TechnoFiles by David PogueDavid Pogue is the anchor columnist for Yahoo Techand host of several NOVA miniseries on PBS.You: By the NumbersCan personal fitness monitors whip us—and health research—into shape?You may have heard of the Fitbit or the UP band: $50-ish ference, it’s communities of people, some of whom are raisingto $100-ish wristbands that measure your steps throughout the self-monitoring to the level of obsession.day, like a high-tech pedometer, and display your progress as agraph on your smartphone. Millions of people making a greater effort to get healthy and fit—who could argue with that? But this product category has exploded well beyond thosecommon names. There’s the Nike+ FuelBand, Garmin Vivofit, There are a couple of obvious problems with the mad rushthe Basis Peak, the Magellan Echo, the Misfit Shine, and on and to quantify ourselves, though—and to sell us gadgets for it.on. Health tracking is also built into the Apple Watch and theSamsung Gear watches. Wearable fitness monitoring has become First, we’re almost certainly ascribing more precision to thesea $1.15-billion industry. devices than they deserve. If you wear three brands of fitness band, you’ll rack up three different step counts by the end of All these gadgets count steps. Most also measure sleep, re each day. And don’t get sleep scientists started on the accuracy ofvealing fascinating details about the one third of your life that those sleep graphs; according to researchers, it’s brain waves,you spend unconscious. The fancier models can also tabulate not wrist movement, that indicate what stage of sleep you’re in.other metrics, including heart rate, blood oxygen level, skin tem-perature, perspiration, body weight and body mass. But you know what? It doesn’t matter. These devices are suc- ceeding not because of their scientific qualities but because of That’s the great appeal. These gadgets allow us, mere un their motivational ones. We all know we should move more andtrained mortals, to gauge what only doctors used to measure. We sleep better—but with slow decline, most of us don’t bother.gain knowledge about the workings of our own bodies—by moni-toring measurements continuously, not once a year at a physical. What the fitness bands do is to keep these issues front-of-mind. There it is, every time you turn on your phone: the latest stats on Meet the quantified-self movement. It’s a Web site, it’s a con- your progress. Most also show the results of friends who wear the same brand; it’s fitness through humiliation. In other words, the accuracy really makes little difference; the point is to keep us aware, to gamify our efforts. In that way, these bands really work. You wind up parking farther away, get- ting off the bus a stop earlier, going for a walk down the block to bring your 9,374 daily step count up to your 10,000-step goal. The other concern is less easily dismissed: the data. Terabytes of personal health data, amassed daily in stunning quantities. It’s the world’s biggest health study—and nobody’s running it. Researchers would love to get their hands on that informa- tion. So would advertisers. Insurance companies would have a field day; they could offer active members lower rates than sed- entary sloths. (Our rates are already higher if we’re smokers or drivers with bad records.) Who owns the data? Will the makers of the fitness bands sell personal information? Will it be anonymous and aggregated or associated with us by name? What if we want to contribute our data—to a doctor? To a research study? It’s the Wild West at the moment. We’re collecting mountains of personal health data and just shoving them into underground caverns. The real promise of the quantified-self movement may not be fulfilled until we determine how to find the gold in those data—and who gets to do the looking. SCIENTIFIC AMERICAN ONLINE Health-monitoring socks and more: ScientificAmerican.com/jan2015/pogueIllustration by Rebekka Dunlap January 2015, ScientificAmerican.com 31 © 2014 Scientific American
E A R T HB E T T E R T H A NASTRONOMY Planets quite different from our own may be the best homes for life in the universe By René Heller32 Scientific American, January 2015 Illustration by Ron Miller © 2014 Scientific American
LARGE, ROCKY “superhabitable” world orbiting a star smaller than our sun might be both familiar and alien. The landscape would be flattened by higher surface gravity, and plants there could be tinted darker than Earth’s greenery to better absorb the faint starlight.© 2014 Scientific American
René Heller is a postdoctoral fellow at the Origins Institute at McMaster University in Ontario and a member of the Canadian Astrobiology Training Program. His research focuses on the formation, orbital evolution, detection and habitability of extrasolar moons. He is informally known as the best German rice pudding cook in the world.Do we inhabit the best of all possible worlds? date, middle-aged star that has shone steadi- German mathematician Gottfried Leibniz ly for billions of years, giving life plenty of thought so, writing in 1710 that our planet, time to arise and evolve. It has oceans of warts and all, must be the most optimal life-giving water, largely because it orbits one imaginable. Leibniz’s idea was roundly within the sun’s “habitable zone,” a slen- scorned as unscientific wishful thinking, most notably by French author Voltaire in hismagnum opus, Candide. Yet Leibniz might find sympathy der region where our star’s light is neitherfrom at least one group of scientists—the astronomers who too intense nor too weak. Inward of thehave for decades treated Earth as a golden standard as they zone, a planet’s water would boil into steam; outward of the area, it would freeze intosearch for worlds beyond our own solar system. ice. Earth also has a life-friendly size: big enough to hold on to a substantial atmo- sphere with its gravitational field but smallBecause earthlings still know of just one living world—our enough to ensure gravity does not pull a smothering, opaqueown—it makes some sense to use Earth as a template in the search shroud of gas over the planet. Earth’s size and its rocky compo-for life elsewhere, such as in the most Earth-like regions of Mars sition also give rise to other boosters of habitability, such as cli-or Jupiter’s watery moon Europa. Now, however, discoveries of mate-regulating plate tectonics and a magnetic field that pro-potentially habitable planets orbiting stars other than our sun— tects the biosphere from harmful cosmic radiation.exoplanets, that is—are challenging that geocentric approach. Yet the more closely we scientists study our own planet’sOver the past two decades astronomers have found more habitability, the less ideal our world appears to be. These daysthan 1,800 exoplanets, and statistics suggest that our galaxy habitability varies widely across Earth, so that large portions ofharbors at least 100 billion more. Of the worlds found to date, its surface are relatively devoid of life—think of arid deserts,few closely resemble Earth. Instead they exhibit a truly enor- the nutrient-poor open ocean and frigid polar regions. Earth’smous diversity, varying immensely in their orbits, sizes and habitability also varies over time. Consider, for instance, thatcompositions and circling a wide variety of stars, including during much of the Carboniferous period, from roughly 350ones significantly smaller and fainter than our sun. Diverse fea- million to 300 million years ago, the planet’s atmosphere wastures of these exoplanets suggest to me and to others that Earth warmer, wetter and far more oxygen-rich than it is now. Crusta-may not be anywhere close to the pinnacle of habitability. In ceans, fish and reef-building corals flourished in the seas, greatfact, some exoplanets, quite different from our own, could have forests blanketed the continents, and insects and other terres-much higher chances of forming and maintaining stable bio- trial creatures grew to gigantic sizes. The Carboniferous Earthspheres. These “superhabitable worlds” may be the optimal tar- may have supported significantly more biomass than our pres-gets in the search for extraterrestrial, extrasolar life. ent-day planet, meaning that Earth today could be considered less habitable than it was at times in its ancient past.AN IMPERFECT PLANET Further, we know that Earth will become far less life-friend-Of course, our planet does possess a number of properties that, ly in the future. About five billion years from now, our sun willat first glance, seem ideal for life. Earth revolves around a se have largely exhausted its hydrogen fuel and begun fusing IN BRIEFAstronomers are searching for twins the edge of our technical capabilities. be the most common type of planet. ing gas-giant planets, may also be su-of Earth orbiting other sunlike stars. perhabitable—more conducive to life Larger “super-Earths” orbiting small- New thinking suggests that these sys- than our own familiar planet.Detecting Earth-like twins remains at er stars are easier to detect and may tems, along with massive moons orbit-34 Scientific American, January 2015 © 2014 Scientific American
more energetic helium in its core, causing it to swell to become Superhabitable planets, on the other hand, may already exista “red giant” star that will scorch Earth to a cinder. Long before within our catalogue of confirmed and candidate exoplanets.that, however, life on Earth should already have come to an The first exoplanets found in the mid-1990s were all gas giantsend. As the sun burns through its hydrogen, the temperature at similar in mass to Jupiter and orbiting far too close to their starsits core will gradually rise, causing our star’s total luminosity to to harbor any life. Yet as planet-hunting techniques have imslowly increase, brightening by about 10 percent every billion proved over time, astronomers have begun finding progressive-years. Such change means that the sun’s habitable zone is not ly smaller planets in wider, more clement orbits. Most of thestatic but dynamic, so that over time, as it sweeps farther out planets discovered over the past few years are so-called super-from our brightening star, it will eventually leave Earth behind. Earths, planets larger than Earth by up to 10 Earth masses, withTo make matters worse, recent calculations suggest that Earth radii between that of Earth and Neptune. These planets haveis not in the middle of the habitable zone but rather on the proved to be extremely common around other stars, yet we havezone’s inner cusp, already teetering close to the edge of over- nothing like them orbiting the sun, making our own solar sys-heating [see box on page 38]. tem appear to be a somewhat atypical outlier.Consequently, within about half a billion years our sun will Many of the bigger, more massive super-Earths have radiibe bright enough to give Earth a feverish climate that will threat- suggestive of thick, puffy atmospheres, making them more like-en the survival of complex multicellular life. By some 1.75 billion ly to be “mini Neptunes” than super-sized versions of Earth. Butyears from now, the steadily brightening star will make our some of the smaller ones, worlds perhaps up to twice the size ofworld hot enough for the oceans to evapo-rate, exterminating any simple life lingering Earth is past its prime,on the surface. In fact, Earth is well past itshabitable prime, and the biosphere is fast-approaching its denouement. All things con- and the biosphere issidered, it seems reasonable to say our plan-et is at present only marginally habitable. SEEKING A SUPERHABITABLE WORLD nearing its end. All thingsIn 2012 I first began thinking about what considered, our planet isworlds more suitable to life might look likewhile I was researching the possible habit-ability of massive moons orbiting gas-giant only marginally habitable.planets. In our solar system, the biggestmoon is Jupiter’s Ganymede, which has amass only 2.5 percent that of Earth—toosmall to easily hang on to an Earth-likeatmosphere. But I realized that there are plausible ways for Earth, probably do have Earth-like compositions of iron andmoons approaching the mass of Earth to form in other plane- rock and could have abundant liquid water on their surfaces iftary systems, potentially around giant planets within their stars’ they orbit within their stars’ habitable zones. A number of thehabitable zones, where such moons could have atmospheres potentially rocky super-Earths, we now know, orbit stars calledsimilar to our own planet. M dwarfs and K dwarfs, which are smaller, dimmer and muchSuch massive “exomoons” could be superhabitable because longer-lived than our sun. In part because of the extended livesthey offer a rich diversity of energy sources to a potential bio- of their diminutive stars, these super-sized Earths are currentlysphere. Unlike life on Earth, which is powered primarily by the the most compelling candidates for superhabitable worlds, as Isun’s light, the biosphere of a superhabitable exomoon might have shown in recent modeling work with my collaborator Johnalso draw energy from the reflected light and emitted heat of its Armstrong, a physicist at Weber State University.nearby giant planet or even from the giant planet’s gravitation-al field. As a moon orbits around a giant planet, tidal forces can THE BENEFITS OF LONGEVITYcause its crust to flex back and forth, creating friction that We began our work with the understanding that a truly long-heats the moon from within. This phenomenon of tidal heating lived host star is the most fundamental ingredient for super-is probably what creates the subsurface oceans thought to exist habitability; after all, a planetary biosphere is unlikely to sur-on Jupiter’s Europa and Saturn’s moon Enceladus. That said, vive its sun’s demise. Our sun is 4.6 billion years old, approx-this energetic diversity would be a double-edged sword for a imately halfway through its estimated 10-billion-year lifetime.massive exomoon because slight imbalances among the over- If it were slightly smaller, however, it would be a much longer-lapping energy sources could easily tip a world into an unin- lived K dwarf star. K dwarfs have less total nuclear fuel to burnhabitable state. than more massive stars, but they use their fuel more efficient-No exomoons, habitable or otherwise, have yet been detect- ly, increasing their longevity. The middle-aged K dwarfs weed with certainty, although some may sooner or later be revealed observe today are billions of years older than the sun and willby archival data from observatories such as nasa’s Kepler space still be shining billions of years after our star has expired. Anytelescope. For the time being, the existence and possible habit- potential biospheres on their planets would have much moreability of these objects remain quite speculative. time in which to evolve and diversify. January 2015, ScientificAmerican.com 35 © 2014 Scientific American
EARTH VS. SUPER-EARTHS Super-Earths’ Big Benefits for Life Astronomers searching for life around other stars increasingly focus on super-Earths: planets larger than our own, by up to 10 Earth masses yet smaller than gas giants and thus potentially rocky. Super-Earths of about two Earth masses are particularly promising targets because they possess certain properties (below) that could render them “superhabitable”—friendlier to life than our own planet is.Life on EarthOur planet has much to recommend it. Orbiting inthe “just right” region of a quiet, middle-aged star,Earth boasts a global ocean that, though deep,is shallow enough to allow for dry land for lifeto inhabit. It is big enough to have a sizableatmosphere but small enough to avoid accumulating life-smothering layers of gas. Mostlymade of rock, Earth also harbors sufficient internalheat to maintain climate-stabilizing plate tectonics and a planet-protecting magnetic field.Life on a Superhabitable World Illustration by Ron Miller (planets) and Jen Christiansen (inset)A rocky, superhabitable super-Earth some two timesmore massive than Earth would have a highersurface gravity, which could lead to a thickeratmosphere, more erosive weather and flattertopography. The result could be an “archipelagoworld” of shallow seas dotted with island chainsrather than a more familiar world of deep oceansand large continents. Such geography could benefitlife, given that Earth’s scattered archipelagoes areamong the most biologically dense and diverse spotson the planet. Even so, the crux of a super-Earth’ssuperhabitability lies far below these surface details,in the planet’s interior (opposite page).36 Scientific American, January 2015 © 2014 Scientific American
Cosmic rays Core spinMagnetic directionfieldA Core That Won’t QuitA rocky super-Earth of about two Earth masses should retainsignificantly more heat within its interior from its initialformation as well as the decay of radioactive isotopes. Thisheat reservoir could create a spinning, molten core similarto Earth’s but much longer-lasting, which would induce apowerful magnetic field around the planet to protect theatmosphere and surface from destructive cosmic rays.Continual Carbon CyclingThe greater convective heat (orange arrows) within a super-Earth could help it to sustain volcanism and plate tectonicsfor longer than they will persist on Earth. These processes arevital for regulating a planet’s carbon cycling and thus itsclimate. Volcanoes vent heat-trapping carbon dioxide intothe atmosphere, which rainfall slowly washes back into rock.Plate tectonics transports those rocks into the planet’sinterior, where the carbon dioxide cooks off, eventuallyreturning to the air via volcanism. Theoretical modelssuggest super-Earths as small as three to five Earth massesmay be too bulky for plate tectonics, making worlds of abouttwo Earth masses better candidates for superhabitability.Steady SunshineRegardless of any planet’s properties, its habitability dependsmost on the star it orbits. Stars smaller than the sun burntheir nuclear fuel more efficiently and can exist for eonslonger, giving their planets far more time to develop robustbiospheres. Tiny, dim stars called K dwarfs can shine for manytens of billions of years, in contrast to our sun’s estimated10 billion years, striking a balance between providing sufficient starlight and having extended longevity. A small super-Earth orbiting in the habitable zone of a K dwarf may residein the sweet spot of superhabitability. January 2015, ScientificAmerican.com 37© 2014 Scientific American
Ha LIFE’S MOMENT IN THE SUN A K dwarf’s light would appear somewhat ruddier than the sun’s, as it would be shifted more toward the infrared, but its As Stars Age, They spectral range could nonetheless support photosynthesis on a Turn Up the Heat planet’s surface. M dwarf stars are smaller and more parsimoni- on Habitable Planets ous still and can steadily shine for hundreds of billions of years, but they shine so dimly that their habitable zones are very close-On human timescales, a star’s habitable zone appears to be in, potentially subjecting planets there to powerful stellar flaresstatic. But because stars brighten as they age, over eons the and other dangerous effects. Being longer-lived than our sun yetzone sweeps outward, eventually leaving living worlds behind. not treacherously dim, K dwarfs appear to reside in the sweetEarth is poised near the inner edge of the sun’s habitable spot of stellar superhabitability.zone and will become too hot to harbor liquid water in some1.75 billion years. Smaller stars shine dimmer and longer than Today some of these long-living stars may harbor potentiallythe sun, scarcely budging their habitable zones over tens of rocky super-Earths that are already several billion years olderbillions of years, potentially extending their planets’ lives. than our own solar system. Life could have had its genesis in these planetary systems long before our sun was born, flourish- bitable zone ing and evolving for billions of years before even the first bio- 3.5 billion years ago molecule emerged from the primordial soup on the young Earth. I am particularly fascinated by the possibility that a bio- Sun Living Earth sphere on these ancient worlds might be able to modify its glob- 1 astronomical unit al environment to further enhance habitability, as life on Earth has done. One prominent example is the Great Oxygenation (150 million kilometers) Event of about 2.4 billion years ago, when substantial amounts of oxygen first began to accumulate in Earth’s atmosphere. The Today oxygen probably came from oceanic algae and eventually led to the evolution of more energy-intensive metabolisms, allowing1.75 billion years from now creatures to have bigger, more durable and active bodies. This advancement was a crucial step toward life’s gradual emergence Dead Earth from Earth’s oceans to colonize the continents. If alien bio- spheres exhibit similar trends toward environmental enhance- ment, we might expect planets around long-lived stars to become somewhat more habitable as they age. To be superhabitable, exoplanets around small, long-lived stars would need to be more massive than Earth. That extra bulk would forestall two disasters most likely to befall rocky planets as they age. If our own Earth were located in the habit- able zone of a small K dwarf, the planet’s interior would have grown cold long before the star expired, inhibiting habitability. For example, a planet’s internal heat drives volcanic eruptions and plate tectonics, processes that replenish and recycle atmo- spheric levels of the greenhouse gas carbon dioxide. Without those processes, a planet’s atmospheric CO2 would steadily decrease as rainfall washed the gas out of the air and into rocks. Ultimately the CO2-dependent global greenhouse effect would grind to a halt, increasing the likelihood that an Earth-like plan- et would enter an uninhabitable “snowball” state in which all of its surface water freezes. Beyond the potential breakdown of a planet-warming green- house effect, the cooling interior of an aging rocky world could also cause the collapse of any protective planetary magnetic field. Earth is shielded by a magnetic field generated by a spin- ning, convecting core of molten iron, which acts like a dynamo. The core remains liquefied because of leftover heat from the planet’s formation, as well as from the decay of radioactive iso- topes. Once a rocky planet’s internal heat reservoir became exhausted, its core would solidify, the dynamo would cease, and the magnetic shield would fall, allowing cosmic radiation and stellar flares to erode the upper atmosphere and impinge on the surface. Consequently, old Earth-like planets would be expected to lose substantial portions of their atmospheres to space, and higher levels of damaging radiation could harm surface life.38 Scientific American, January 2015 Illustration by Jen Christiansen © 2014 Scientific American
Rocky super-Earths as much as twice our planet’s size statistics from exoplanet surveys suggest that super-Earthsshould age more gracefully than Earth, retaining their inner around small stars are substantially more abundant throughoutheat for much longer because of their significantly greater our galaxy than Earth-sun analogues. Astronomers seem tobulks. But planets larger than about three to five Earth masses have many more tantalizing places to hunt for life than previ-may actually be too bulky for plate tectonics because the pres- ously believed.sures and viscosities in their mantles become so high that they One of Kepler’s prize finds, the planet Kepler-186f, comes toinhibit the required outward flow of heat. A rocky planet only mind. Announced in April 2014, this world is 11 percent largertwo times the mass of Earth should still possess plate tectonics in diameter than Earth and probably rocky, orbiting in the hab-and could sustain its geologic cycles and magnetic field for sev- itable zone of its M dwarf star. It is probably several billioneral billion years longer than Earth could. Such a planet would years old, perhaps even older than Earth. It is about 500 light-also be about 25 percent larger in diameter than Earth, giving years away, placing it beyond the reach of current and near-any organisms about 56 percent more surface area than our future observations that could better constrain predictions ofworld on which to live. its habitability, but for all we know, it could be a superhabitable archipelago world.LIFE ON A SUPERHABITABLE SUPER-EARTH Closer superhabitable candidates orbiting nearby smallWhat would a superhabitable planet look like? Higher surface stars could soon be discovered by various projects, most nota-gravity would tend to give a middling super-Earth planet a bly the European Space Agency’s PLATO mission, slated toslightly more substantial atmosphere than Earth’s, and its launch by 2024. Such nearby systems could become primemountains would erode at a faster rate. In other words, such a targets for the James Webb Space Telescope, an observatoryplanet would have relatively thicker airand a flatter surface. If oceans were Superhabitable worldspresent, the flattened planetary land-scape could cause the water to pool inlarge numbers of shallow seas dottedwith island chains rather than in greatare slightly larger thanabyssal basins broken up by a few verylarge continents [see box on pages 36 Earth and orbit stars thatand 37]. Just as biodiversity in Earth’s are somewhat smalleroceans is richest in shallow waters nearcoastlines, such an “archipelago world”might be enormously advantageous tolife. Evolution might also proceed more and dimmer than the sun.quickly in isolated island ecosystems,potentially boosting biodiversity.Of course, lacking large continents,an archipelago world would potentiallyoffer less total area than a continental world for land-based life, scheduled to launch in 2018, which will seek signs of lifewhich might reduce overall habitability. But not necessarily, within the atmospheres of a small number of potentially suespecially given that a continent’s central regions could easily perhabitable worlds. With considerable luck, we may all soonbecome a barren desert as a result of being far from temperate, be able to point to a place in the sky where a more perfecthumid ocean air. Furthermore, a planet’s habitable surface area world exists. can be dramatically influenced by the orientation of its spinaxis with respect to its orbital plane around its star. Earth, as MORE TO EXPLOREan example, has a spin-orbit axial tilt of about 23.4 degrees, giv-ing rise to the seasons and smoothing out what would other- Habitable Climates: The Influence of Obliquity. David S. Spiegel, Kristen Menouwise be extreme temperature differences between the warmer and Caleb A. Scharf in Astrophysical Journal, Vol. 691, No. 1, pages 596–610;equatorial and colder polar regions. Compared with Earth, an January 20, 2009. http://iopscience.iop.org/0004-637X/691/1/596/articlearchipelago world with a favorable spin-orbit alignment couldhave a warm equator as well as warm, ice-free poles and, by vir- Exomoon Habitability Constrained by Illumination and Tidal Heating.tue of its larger size and larger surface area on its globe, would René Heller and Rory Barnes in Astrobiology, Vol. 13, No. 1, pages 18–46; 2013.potentially boast even more life-suitable land than if it had http://arxiv.org/abs/1209.5323large continents. Habitable Zone Lifetimes of Exoplanets around Main Sequence Stars. Taken together, all these thoughts about the features impor- A ndrew J. Rushby, Mark W. Claire, Hugh Osborn and Andrew J. Watson in Astrobiology, Vol. 13, No. 9, pages 833–849; September 18, 2013. Superhabitable Worlds. René Heller and John Armstrong in Astrobiology, Vol. 14, No. 1, pages 50–66; January 16, 2014. http://arxiv.org/abs/1401.2392tant to habitability suggest that superhabitable worlds are FROM OUR ARCHIVESslightly larger than Earth and have host stars somewhat smallerand dimmer than the sun. If correct, this conclusion is tremen- Planets We Could Call Home. Dimitar D. Sasselov and Diana Valencia; August 2010.dously exciting for astronomers because across interstellar dis- The Dawn of Distant Skies. Michael D. Lemonick; July 2013.tances super-Earths orbiting small stars are much easier to The Search for Life on Faraway Moons. Lee Billings; January 2014.detect and study than twins of our own Earth-sun system. So far sc i e n t i f i ca m e ri ca n .co m /m a g a z i n e /saS CIENTIFIC AMERICAN ONLINE Learn more about superhabitable super-Earths at ScientificAmerican.com/jan2015/heller © 2014 Scientific American
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FWBoreaAMEtDcIaCINErkteeınsnrseıas’ss Evolutionary biologists are trying to attack bacteria in a new way: by short-circuiting their social life By Carl ZimmerAt the University of Zurich, Rolf Kümmerli investigates new drugs to stop deadly infections. He spends his days in a laboratory stocked with petri dishes and flasks of bacteria—exactly the place where you would expect him to do that sort of work. But Kümmerli took an odd path to get to that lab. As a graduate student, he spent years hiking through the Swiss Alps to study the social life of ants. Only after he earned a Ph.D. in evolutionary biology did he turn his attention to microbes.Researchers from an emerging field called sociomi IN BRIEF tance to such “antisocial” drugs should be difficult.crobiology believe they have a new approach to fight Not everyone is convinced, however, that this new They want to disrupt the processes that allow bacteria strategy for developing antibiotics will work.antibiotic resistance among illness-causing bacteria. to communicate and cooperate with one another. Evolutionary theory predicts that acquiring resisPhotography by Zachary Zavislak January 2015, ScientificAmerican.com 41 © 2014 Scientific American
The path from ants to antibiotics is not as roundabout as it Carl Zimmer is a columnist at the New York Timesmay seem. For decades scientists have studied how cooperative a nd author of 13 books, including Evolution: Makingbehavior evolves in animal societies such as ant colonies, in which Sense of Life. His last article for Scientific Americansterile female workers raise the eggs of their queen. A new branch was about the oldest rocks on the earth.of science—sometimes called “sociomicrobiology”—is revealingthat some of the same principles that govern ants can explain the happening. Today, of course, scientists can probe the evolution ofemergence of bacterial societies. Like ants, microbes live in com- resistance in all its molecular details.plex communities, where they communicate with one another tocooperate for the greater good. This insight of social evolution sug- Penicillin, for example, kills bacteria by grabbing onto a pro-gests a new strategy for stopping infections: instead of attacking tein that helps in building the bacteria’s cell membranes. Withoutindividual bacteria, as traditional antibiotics do, scientists are ex- this protein, a bacterium will spring a leak and die. In any popula-ploring the notion of attacking entire bacterial societies. tion of bacteria, a few mutants will be able to defend themselves against penicillin. Bacteria, for example, have pumps to flush tox- New strategies are exactly what is needed now. Bacteria have ic chemicals out of their interior. A mutant microbe may produceevolved widespread resistance to antibiotics, leaving doctors in a extra pumps, allowing it to rid itself of penicillin quickly, freeingcrisis. For example, the Centers for Disease Control and Preven- up its proteins to build its membranes.tion estimates that 23,000 people die in the U.S. every year ofantib iotic-resistant infections. Strains of tuberculosis and other Normally such a mutation does not provide any evolution-pathogens are emerging that are resistant to nearly every drug. ary advantage to a microbe. If a patient takes a dose of penicil-“It already is a substantial problem,” says Anthony S. Fauci, di- lin to clear an infection, suddenly those extra pumps can makerector of the National Institute of Allergy and Infectious Disease. a huge difference. Bacteria without the extra pumps die, where-“And there’s every reason to believe it’s going to get even worse.” as many mutants manage to survive. The survivors multiply, in- creasing the proportion of mutants in the population. In subse- The standard response to this crisis has been to slow the evo- quent generations, the descendants of the original mutantslution of resistance and find new drugs to replace old ones as may evolve even better defenses, sometimes by picking upthey grow weak. But this is only a treadmill solution. Bacteria are genes from other bacterial species.relentlessly evolving resistance and will continue to do so unlesswe find a different way to fight them. “Every time we develop a For decades new drugs came out of the development pipelinenew drug, it fails,” says John Pepper, a theoretical biologist at the quickly enough to replace the old ones that failed. But now thatNational Cancer Institute. “So the solution is, ‘Quick! Make an- pipeline is drying up. As the expense of developing new antibiot-other antibiotic!’ That helps for a few months. But that’s just not ics has cut into profits, many pharmaceutical companies havegood enough any more.” bailed out of the antibiotics business and invested instead in more profitable drugs for cancer or hepatitis. Many infectious species of bacteria depend on their collectivebehavior to make us sick. Sociomicrobiologists are looking for As the crisis deepened, scientists yearned for an antibioticopportunities to disrupt their societies—by interfering with their that would not become obsolete. And sometimes they did findcommunication, for example, or blocking their cooperative ef- what they believed to be an evolution-proof drug. In 1987, for ex-forts to gather nutrients. Evolutionary theory predicts that the ample, Michael Zasloff, then at the nih, discovered that Africancollective behavior of bacteria should be a ripe target for medi- clawed frogs produce a powerful toxin against bacteria in theircine. Attacking the social life of bacteria may not be a completely skin. Zasloff and other researchers soon found that the amphibi-evolution-proof strategy. But at the very least, it might slow ans were not the only toxin makers. Just about every animal theydown the evolution of resistance dramatically. looked at made small, positively charged proteins that could kill bacteria—a class of molecules that came to be known as antimi- Sociomicrobiologists have a lot of skepticism to overcome. Al- crobial peptides.though they have presented detailed theoretical arguments anda few promising experimental results, some researchers doubt In journal reviews and in news reports, Zasloff predicted thatthat their evolution-inspired drugs will be able to stop the rise of bacteria would be unlikely to evolve resistance against the drugs.resistance. And pharmaceutical companies, which have shied Animals, he pointed out, had been using antimicrobial peptidesaway from antibiotics in general, are not yet ready to push such to kill bacteria for hundreds of millions of years, and yet bacteriadrugs through the approval pipeline and into the marketplace. today remain vulnerable to the peptides. In 2003 Graham Bell, an evolutionary biologist at McGill University, predicted that Still, the sociomicrobiologists are getting some attention. The Zasloff would be proved wrong. Penicillin and many otherNational Institutes of Health has been laying plans for research drugs had also been discovered being made in nature. But mod-into antibiotic resistance, and investigators have made the social ern medicine delivered them in huge concentrations to pa-life of bacteria a top priority. If the work pans out, they will have tients—thereby creating a tremendous evolution pressure thatsucceeded in reversing the relation between medicine and evolu- drove the rise of resistant mutants. As soon as doctors startedtion. Traditionally an enemy in the fight against bacteria, evolu- giving pills packed with antimicrobial peptides to patients, his-tion would become a friend. tory would repeat itself. THE EVOLUTION OF DRUG RESISTANCE Zasloff challenged Bell to see if bacteria could become resis-The crisis of antibiotic resistance has been long in the making. Afew years after the first antibiotics were introduced in the mid-1900s, doctors had already discovered some bacteria that couldwithstand them. At the time, it was not entirely clear what was42 Scientific American, January 2015 © 2014 Scientific American
CASE STUDY Lessons from Evolutionary BiologyResearchers hope to develop more effective antibacterial treat- drug resistance, in theory, because no single cell should be able profitments by interfering with the way various germs communicate and by changing the way it responds. One idea, which targets a moleculecooperate with one another. Such an approach should trigger less that Pseudomonas bacteria use to scavenge iron, is shown below.The Target: 3a Bacterial cells reabsorb theCommunal Nutrient Gathering siderophores (though usually notPseudomonas bacteria produce molecules called the exact ones they produced) andsiderophores to steal iron from their host, as the use the iron to fuel cell division.pathway in blue indicates. Each siderophore can be Ironreused by many different germ cells and in thatway is a public, rather than a private, good. FEED Siderophore 2a Siderophores wrestle iron away from host molecules. P. aeruginosa 1 Siderophore release 2b Gallium, which has many chemical similarities to iron, is introduced as a drug; the siderophores pick up gallium instead of iron.Strategy: STARVE GalliumDeplete Shared Goods 3b Siderophores return to theItems in magenta highlight an approachinspired by sociomicrobiology: undercut bacterial colony with gallium,the service rendered by a shared substance. which the cells cannot use,Here delivery of gallium undermines the ability of thus stopping their growth.siderophores to provide iron to the bacterial population.Even if a single cell develops a favorable siderophoremutation, that cell will still probably starve because it islikely to take up siderophores made by other bacteria.tant to pexiganan, one of his best-studied peptides. Bell and his Today we do not know for sure if that is actually true, and wethen graduate student Gabriel Perron reared a batch of Escherich- will not unless antimicrobial peptides are eventually approvedia coli and exposed it to a low dose of pexiganan. Then they took for use for infections. Currently pharmaceutical companies aresome of the surviving bacteria to start a new colony, which they running several clinical trials, but 28 years after their discovery,exposed to a higher dose of the drug. Increasing the dose over a not a single antimicrobial peptide has been approved for use forfew weeks, the scientists watched the bacteria evolve to be com- infections. They are victims of a slow pipeline.pletely resistant to pexiganan, just as Bell had predicted. COOPERATION AMONG BACTERIA Zasloff immediately acknowledged that Bell had been right. Charles Darwin could have had no idea that bacteria would be-The experiment made him far more cautious about antimicrobi- come one of the best illustrations of his theory of natural selec-al peptides. “If something can happen in a test tube, it is very tion. He and other scientists of his day knew very little aboutlikely that it can happen in the real world,” Zasloff told Nature. how microbes grow. When he presented his theory in On the Ori-(Scientific American is part of Nature Publishing Group.)Illustration by John Grimwade January 2015, ScientificAmerican.com 43 © 2014 Scientific American
gin of Species in 1859, he instead wrote about traits that were fa- ENEMY GROUP: The collective activities of Pseudomonas STEVE GSCHMEISSNER Science Sourcemiliar to his fellow Victorians, like the fur on mammals and the aeruginosa bacteria, pictured in the electron micrograph above,colors of feathers. allow them to trigger hard-to-eradicate infections. Darwin also wrote about familiar features of nature that had advantage. A mutant that does not make siderophores can still getinitially made him worry that his idea might be wrong. One of iron without paying the cost of making siderophores. It should re-them was that in many species of ants, female workers are sterile. produce faster than cooperative bacteria and become more com-In Darwin’s theory, natural selection emerged from the competi- mon. And yet it is the cooperators that dominate species such astion between individuals to survive and reproduce. But worker P. aeruginosa, not the freeloaders.ants, which do not reproduce themselves, seemed to be droppingout of the competition altogether. Their existence, Darwin wrote, In the mid-2000s a small group of evolutionary biologists be-seemed to be “actually fatal to my whole theory.” gan to turn their attention to these intriguing questions about the social life of bacteria. The University of Edinburgh emerged Darwin suspected that a solution to the worker ant paradox as a leading center for sociomicrobiology, which is why Küm-lay in kinship. An ant colony is not just a random jumble of merli went there in 2007. He did not immediately start runningstrangers. It is more like an extended family. Together a group of experiments, though. Years of studying ants had not yet pre-related ants may be able to produce more offspring than if they pared him for the hard work of microbiology. Kümmerli and oth-all try to breed on their own. er aspiring sociomicrobiologists had to apprentice themselves in the microbiological arts. They learned how to rear bacteria, how Darwin’s ideas on cooperation have inspired generations of to prevent their stocks from getting contaminated, how to ma-evolutionary biologists to explore them further. That is how Küm- nipulate their genes and how to run experiments. “It took yearsmerli got his start as a scientist. He would sequence DNA from to learn all the methods,” Kümmerli says. “Sometimes we wereants in different nests, for example, to see how their kinship influ- not taken seriously by the classical microbiologists.”enced their behavior toward one another. The research was fasci-nating but also slow and limited. As Kümmerli got closer to earn- Eventually they got results. They began uncovering tricksing his Ph.D., he discovered some evolutionary biologists who that social bacteria use to keep freeloaders at bay. Working withwere switching from social animals to social bacteria. Brown, for example, Kümmerli found that Pseudomonas bacte- ria do not produce a steady stream of siderophores. Instead they The words “social” and “bacteria” may not be tightly joined in churn them out suddenly, in an initial burst. Once the bacteriamost people’s minds, but it turns out that microbes live in intimate have created a supply of siderophores, they can recycle the mole-communities full of conversation and cooperation. Take Pseudo- cules. They absorb iron-bearing siderophores, pull away the ironmonas aeruginosa, a species that can cause serious lung infections. atoms and then spit the siderophores back out. Thanks to the du-When one of the microbes invades a host, it sends out signaling rability of siderophores, the bacteria do not have to use up muchmolecules. Other members of its species can grab those molecules energy making new siderophores to replace old ones. Recyclingwith special receptors. Releasing and grabbing these molecules is thus lowers the cost of cooperation. It also helps to cut down thea way for bacteria to say, “I’m here—is anyone else here?” advantage of being a freeloader. If the bacteria sense that they do have enough members, they As the sociomicrobiologists discovered more about the socialwill begin to cooperate to build a shelter. They spray out gooey evolution of bacteria, they began to wonder if they could applymolecules that grow into a mat, inside of which the bacteria em- their insights in a very practical way: by finding new kinds ofbed themselves. This so-called biofilm can stick to the lining of drugs to fight infections.the lungs or other organs. Nestled deep inside the biofilm, thebacteria are shielded from the attacks of immune cells. Pseudomonas bacteria also work together to gather nutrients.Bacteria cannot grow without iron, for example, but the humanbody is a tough place to find it because our cells snap up iron andlock it away in hemoglobin and other molecules. To get an ironsupply, each microbe releases molecules called siderophores. Thesiderophores can wrest the atoms away from our own molecules.“They basically steal the iron,” says Sam Brown, an evolutionarybiologist at the University of Edinburgh. The bacteria can thenabsorb the iron-bearing siderophores and use the iron to grow. The effort is deeply cooperative because each siderophorethat a microbe takes in was probably made by one of its millionsof neighbors. “One cell will pay a cost that will benefit the wholeinfection, not that one cell,” the nci’s Pepper says. Evolutionarytheorists have a name for such molecules: public goods. Thesemolecules are good for the public at large—in this case, the com-munity of bacteria. They are the opposite of private goods, whichonly benefit the individual bacteria that made them. Public goods represent a Darwinian paradox. Natural selec-tion should, in theory, wipe them out. Mutants that do not maketheir own public goods can still use the public goods made by oth-ers. This imbalance should put the freeloader at an evolutionarySCIENTIFIC AMERICAN ONLINE Watch a video about the social life of bacteria at ScientificAmerican.com/jan2015/social-bacteria © 2014 Scientific American
TIPPING POINT “I think it’s exactly what was needed as a next step,” he observes.To an evolutionary biologist, all antibiotics in use today are ba- “I hope this will be a tipping point for people.”sically the same. Each attacks bacteria’s private goods. If a mi-crobe mutates to protect its own private goods, it will outcom- Kümmerli hopes that other scientists will start testing galli-pete other bacteria that cannot. Sociomicrobiology reveals a um in infected mice and, perhaps in a few years, in humans.different target for stopping infections. “Instead of targeting Such trials would be relatively easy to run because gallium hasthe individual cells, target their public goods,” Pepper says. already been extensively tested in humans for a number of med- ical treatments. Evolutionary theory predicts that bacteria will be less likelyto evolve resistance to drugs that go after public goods. Imag- POTENTIAL DRUGSine, for example, that researchers were to develop a drug that Siderophores are just one of a number of public goods that so-attacked siderophores. As a result, bacteria would become starved ciomicrobiologists are studying as potential targets for drugs.of iron. Some bacteria, for example, make us sick by releasing toxins. But they only do so once their population is big enough to de- Now imagine that an individual microbe acquired a mutation liver a potent wallop. Then they unleash toxins that cause ourthat protected its siderophores from the drug. That mutant cells to rupture, spilling out molecules that the bacteria canwould not gain any advantage. Bacteria collectively release all feed on. Drugs that can disarm toxins may be able to rendertheir siderophores into their host, where the molecules get mixed bacteria helpless without even killing them.up. When a microbe takes up an iron-bearing siderophore, it is al-most certainly not one of its own. As a result, mutants cannot Other researchers are investigating the signals that bacteriaoutreproduce their fellow bacteria. send to one another. They are discovering molecules that can jam this communication in various ways, such as blocking the Sociomicrobiologists first developed this argument in the receptors that usually grab signaling molecules. If bacteria can-abstract, through mathematical equations and computer simu- not communicate with one another, then they cannot cooperate.lations. “We devise all these theories and say look, this ought towork if you just try it,” Pepper says. “But all that effort is useless Antisocial drugs could have another advantage over conven-if no one is going to try it.” Those experiments are now under tional antibiotics: instead of wiping out lots of species of bacte-way. Recently, for example, Kümmerli, Brown and their col- ria at once, they may be able to narrow their targets. That is be-leagues tried out a drug that attacks siderophores. Previous re- cause the public goods made by one species are typically onlysearch had revealed that siderophores made by Pseudomonas useful to that species alone. Thus, antisocial drugs might beg rab a metal called gallium just as easily as they grab iron. The less likely to wipe out good germs along with the bad.researchers wondered if they could use gallium as a drug tostarve the bacteria of iron. As promising as this research may be, however, some scien- tists are skeptical that antisocial drugs will avoid resistance. To find out, they ran an experiment on caterpillars. They in- Thomas Wood of Pennsylvania State University and his col-fected the insects with Pseudomonas and let the infection run leagues have been investigating a few of the most promising ofits course in some of the insects, which all died. But the infected these compounds. And their results are sobering. In an experi-caterpillars that were given gallium all recovered. ment on a drug that interferes with bacterial signaling, for ex- ample, they found mutants that could grow in spite of the drug. Having shown that gallium could act as an antibacterial In other words, the bacteria evolved a way to live without adrug, the scientists ran another experiment to see if the bacte- public good. “I’m not hopeless,” Wood says. “I just don’t thinkria could evolve resistance to it. Evolutionary theory predicted this one class of drugs is a panacea.”that they should not. “We were quite nervous doing the experi-mental evolution,” Kümmerli says. He and his colleagues knew It is possible that Wood’s results mean that certain publicvery well how other promising drugs had been crushed by the goods are not truly essential. If that is so, then evolution-basedpower of evolution. “We were just hoping no evolution came drugs will have to target only the essential ones.up,” he adds. Even if antisocial drugs turn out only to slow down resistance, For their new experiment, the scientists reared Pseudomonas Pepper says, they will be an important advance. “We’re losing thisin a broth that included iron. But the iron was bound up in mol- race, and lives are at stake,” he declares. “Even if we can just gainecules that the bacteria could not absorb. They needed to use an edge against our opponent, that’s going to save a lot of lives.” their siderophores to pry the iron away from the molecules tosurvive. In one set of trials, the scientists exposed the bacteria to MORE TO EXPLOREsome conventional antibiotics. At first, the drugs rapidly sloweddown the growth of the bacteria. But after 12 days of exposure, Hacking into Bacterial Biofilms: A New Therapeutic Challenge. Christophe Bordithe bacteria became completely resistant to the antibiotics. and Sophie de Bentzmann in Annals of Intensive Care, Vol. 1, Article No. 19; June 13, 2011. www.ncbi.nlm.nih.gov/pubmed/21906350 Then they ran the experiment all over again, this time expos-ing the bacteria to gallium instead of conventional antibiotics. Gallium-Mediated Siderophore Quenching as an Evolutionarily RobustThe gallium drastically slowed down the growth of the bacteria. Antib acterial Treatment. Adin Ross-Gillespie et al. in Evolution, Medicine, andAfter 12 days, the bacteria were just as vulnerable to gallium as Public Health, Vol. 2014, No. 1, pages 18–29; 2014. www.ncbi.nlm.nih.gov/they had been at the start. The experiment met the predictions pubmed/24480613of the sociomicrobiologists. A drug that targeted public goodshad prevented bacteria from evolving resistance. FROM OUR ARCHIVES Pepper, who was not involved in the experiment, considers The Challenge of Antibiotic Resistance. Stuart B. Levy; March 1998.the gallium experiment a major success for sociomicrobiology. Battling Biofilms. J. W. Costerton and Philip S. Stewart; July 2001. sc i e n t i f i ca m e ri ca n .co m /m a g a z i n e /sa January 2015, ScientificAmerican.com 45© 2014 Scientific American
TECHNOLOGY A World — o f —Movement A new “motion microscope” reveals tiny changes in objects—and people—that appear to be stock-still By Frédo Durand, William T. Freeman and Michael Rubinstein Illustration by Sean McCabe© 2014 Scientific American
© 2014 Scientific American
Frédo Durand works on computational photography as a professor of electrical engineering and computer science at the Massachusetts Institute of Technology. William T. Freeman, a professor of electrical engineering and computer science at M.I.T., studies how machine learning can be applied to computer vision. Michael Rubinstein is a research scientist at Google, working on computer vision. His motion microscope work was done while he was at Microsoft Research and M.I.T.T he first microscopes, in the 1500s and 1600s, transformed glass panes that looked completely transparent into a universe teeming with bacteria, cells, pollen and intricate crystals. These visionary aids were the first devices to show people that there were cells within a drop of blood. Since then, microscopes have opened up other invisible worlds for scientists, going within cells or down to the scale of atoms. We believe a new kind of microscope is about to unveil anoth- suring smartphone app called Cardiio.) We felt the calculationser fascinating new world: a world of motion and color change were tricky and more complex than they needed to be, involv-too minute for the eye to catch. Blood pulsing through one’s face ing advanced linear algebra. We began searching for a simplermakes it redder and then lighter, the wind can cause construc- way to carry out the process.tion cranes to sway by a tiny amount, and a baby’s breathing isoften too subtle too be seen. These movements are almost The main challenge is the low degree of the color change inunimaginably small, yet their importance looms large. They can any individual video pixel caused by blood flow—it varies byreveal the state of our health or the vibrations of a crucial just 0.2 percent over the course of a pulse. Unfortunately, cam-machine about to fail. With our students and collaborators, we era sensors do not record exact values and always contain ran-have developed what we call a motion microscope, a tool that dom noise, typically higher than 0.2 percent. This noise vastlycouples a video camera with specialized computation. Together overshadows the variation in redness.they amplify movements in people and objects that seem, to thenaked eye, to be standing absolutely still. In our search for a simpler route, we, along with our then student Hao-Yu Wu, researcher John Guttag of the Massachu- C ALCULATING COLOR setts Institute of Technology and Eugene Shih, then at QuantaOur motion microscope was discovered serendipitously. We had Research Cambridge, decided to replace the number represent-been working on a video project to measure tiny color changes, ing the color of each pixel with an average of all nearby pixels.too small to be seen by the unaided eye. Scientists Ming-Zher This method dramatically reduced the noise because these ran-Poh, Daniel McDuff and Rosalind W. Picard of the M.I.T. Media dom fluctuations tend to cancel one another out within a largeLab had shown, in 2010, that they could use a video camera to enough pixel group. We also filtered out color changes thatmeasure a pulse by detecting minuscule color variations caused occurred over a longer or shorter period than the range typicalby blood flowing to and from the face in rhythm with the beats of the resting pulse for adults.of the heart. (They have turned the technique into a pulse-mea- Our simple approach proved successful at converting the pix- el changes into the number of beats per minute. But these color changes were invisible to us, and we wanted to see what theyAlthough they appear to be absolutely still, objects IN BRIEF These magnified movements can show crucialand people move in ways imperceptible to normal health indicators such as changes in pulse or blood By amplifying color changes in video pixels as theyvision. These movements can be as small, and as change moment by moment, researchers have creat flow or looming safety problems such as abnormal vi ed a “motion microscope” that makes these small moimportant, as a baby’s breaths. tions very visible. brations in heavy machinery.48 Scientific American, January 2015 © 2014 Scientific American