Discover: The Science that Matters (January 2020)

®DiscoverSCIENCE FOR THE CURIOUSTOP 50 STORIESON …i DNA TESTSi CBDi SPACEFLIGHTi GENE THERAPYi MARS EXPLORATION... AND MORE!SPECIAL ISSUEScienceThethat2020MattersJANUARY/FEBRUARY 2020BONUS ONLINE CONTENT CODE p. 3





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JANUARY/FEBRUARY 2020 DISCOVER. 31.Humanity’s First Look at a Black Holep. 8A planet-sized telescope gives us an unprecedented view.BY KOREY HAYNES2. Gene Therapy Gets Clinicalp. 12CRISPR and other tools move out of the lab.BY LINDA MARSA3. Race for the Moon p. 14A new wave of exploration revs up.BY KOREY HAYNESContentsTop 50 Science Stories That Matter DJANUARY/FEBRUARY 2020 VOL. 41, NO. 1Website access code: DSD2001Enter this code at: www.DiscoverMagazine.com/code to gain access to exclusive subscriber content.

4.A Million Species in Dangerp. 17Humans push more plants and animals to the brink.BY RONI DENGLER5. Decoding the Denisovansp. 18New fossils and genetic clues flesh out the hominins.BY NATHANIEL SCHARPING6. The CBD Cure-All? p. 20Spotty research isn’t slowing the cannabidiol boom.BY JEANNE ERDMANN7. Mini-Brains Make New Waves p. 22Lab-grown organoids get connected and electric.BY TEAL BURRELL8. Exploring the Farthest World Yet p. 24New Horizons’ flyby of a distant rock is a new milestone.BY KOREY HAYNES9. Researchers React to Human Genes in Monkeys p. 26A controversial experiment raises ethics concerns.BY TEAL BURRELL10. A Melting Planet p. 28The world’s ice is thawing at an accelerated rate.BY DANIEL BASTARDO BLANCODEPARTMENTSEditor’s Notep. 7Science stoked our curiosity this year like never before. Join in the awe. Images of the Yearp. 92In 2019, more than a black hole caught our eye.BY GEMMA TARLACH20 Things You Didn’t Know About ... New Speciesp. 98Celebrate the new additions to the Tree of Life, from superhero fish to fashonisto spiders.BY GEMMA TARLACH... and Many More (11-50): Archaeology/Paleontology/Anthropology #17 New member of our family tree found in Philippines ....42 #19 Lots o’ Motza! An ancient city rediscovered ......................44#20 Most massive T. rex ever died old and battle-worn ........46 #23 Skull is oldest human fossil outside Africa ..........................51 #36 Unique ancient bird preserved in amber..............................70 #39 An old tooth and a new view of evolution ...........................74 #44 Oldest fossil fungi hints at early “modern” life ..................80 #49 A museum’s monster find .............................................................88Earth/Environment/Energy #22 Volcano early warning system rumbles to life ...................50 #34 Unearthing quakes ...........................................................................67 #43 Rain, rain, here to stay? ..................................................................78 #46 Early start for our first continents .............................................82 #47 Smells like Sargassum....................................................................84Flora and Fauna #32 A bee plus in math ............................................................................64 #50 Rock-eating shipworm shocker .................................................90Math/Physical Sciences #25A quantum jump caught in slo-mo ..........................................54 #28Circuit sensitivity is all in the (mathematical) family ......58 #29Our universe’s forgotten first molecule .................................59 #41Long live the kilogram ....................................................................76Medicine/Genetics #11The first gene-edited babies turn 1 .........................................32 #18Editing out HIV ...................................................................................43#30 Navigating the murky waters of DNA testing ....................60 #33 A microsope that sees DNA ........................................................66 #35 Genes bring clarity to anorexia ..................................................68 #48 Abra-cadaver! Blood vessels come to life ...........................86Neuroscience/Behavior #13 Brains brought back to life ...........................................................35 #26 New form of dementia strikes the “oldest old” ..................54 #38 Reading minds, aloud .....................................................................72 #45 EEGs eke out buried brain activity ..........................................81Policy #27 Measles returns ..................................................................................56 #31 A paradigm shift for depression treatment .........................62Space/Cosmology #12 The bumpy road to launching a Dragon ...............................34 #14 Remembering the Opportunity rover .....................................36 #21 Talking to a twin traveler ...............................................................48 #24 InSight’s frustrating first year on Mars ...................................52 #37 The mystery of Mars’ raging rivers ..........................................72 #42 A surprise slash across Saturn’s largest moon .................76Tech/Entertainment/Culture #15 Mind-controlled rats are now a thing .....................................38 #16 The rules of the road to quantum supremacy ....................40 #40 Elon Musk wants to read your mind .......................................75On the CoverSCIENCE PHOTO LIBRARY — PASIEKA/ GETTY IMAGES4DISCOVERMAGAZINE.COM® ® ® ® ® ®® ®DiscoverSCIENCE FOR THE CURIOUSTOP 50 STORIESON …› DNA TESTS› CBD› SPACEFLIGHT› GENE THERAPY› MARS EXPLORATION... AND MORE!SPECIAL ISSUEScienceThethat2020Matt ers® ® ® ® ®® ®JANUARY/FEBRUARY 2020

In 2009, the United States Mint made history (but not in the way they wanted) when they released the nation’s first Native American Golden Dollar, featuring Sacagawea on the obverse and one-year-only Native American reverse designs. Over the course of several years, a corrupt U.S. officer stole and smuggled out an entire hoard’s worth of coins, each taken before a crucial step in the minting process could be completed—the addition of edge lettering.Why Steal Unfinished Coins?In the coin world, rarity means value. Not only were the stolen coins highly coveted first-year issues but, more importantly, their missing edge lettering made them “error coins,” increasing their scarcity even more. The thief knew this would drive their value up even further.Just how rare are these coins? Only 1,118 of the 39,000,000 coins struck as part of the 2009 Golden Dollar mintage are error dollars that bear the grade, designation and signature of the coin we’re offering today. That’s less than 0.0029% of the entire 2009 Golden Dollar mintage!Officially Authenticated Error DollarsNot only are these 2009 Golden Dollar error coins now legal to own, but they’ve also been professionally authenticated as error coins by Professional Coin Grading Service (PCGS) and certified as being in collector-grade Mint State-66 (MS66) condition. In addition, each coin comes sealed in a protective holder bearing the autograph of Edmund C. Moy, the former Director of the U.S. Mint who held the office when the coins were stolen.Buy Now Before OurLimited Supply Runs Out!Due to the uniqueness of the error and the extremely small number of Gold Error Dollars, the PCGS price guide currently lists their value at a whopping $250 each. But thanks to our eagle-eyed buyers, we secured a small number of these coins for savvy customers. Secure your 2009 Golden Error Dollars for just $99 each. Buy two or more and receive FREE Shipping!We have only a handful of these coins to go around. Don’t let them escape your collection—secure yours now!2009 Native American Error Dollar PCGS MS66 Signed by Edmund Moy- $99 ea.+ s/hFREE SHIPPING on 2 or More!Limited time only. Product total over $149 before taxes (if any). Standard domestic shipping only. Not valid on previous purchases.C all today toll-free for fastest service1-888-201-7070Offer Code NAD337-01Please mention this code when you call.GovMint.com® is a retail distributor of coin and currency issues and is not affi liated with the U.S. government. The collectible coin market is unregulated, highly speculative and involves risk. GovMint.com reserves the right to decline to consummate any sale, within its discretion, including due to pricing errors. Prices, facts, fi gures and populations deemed accurate as of the date of publication but may change signifi cantly over time. All purchases are expressly conditioned upon your acceptance of GovMint.com’s Terms and Conditions (www.govmint.com/terms-conditions or call 1-800-721-0320); to decline, return your purchase pursuant to GovMint.com’s Return Policy. © 2019 GovMint.com. All rights reserved.GovMint.com • 14101 Southcross Dr. W., Suite 175, Dept. NAD337-01 • Burnsville, MN 55337STOLEN FROM THE U.S. MINT!The Secret of the U.S. Dollar Valued at $250 ExplainedValued at $250.00 by PCGSActual size is 26.5 mmONLY$99ea.Missing Edge LetteringEdge Lettering

Experience otality 2020 Tin Discover®MAGAZINESCIENCE FOR THE CURIOUSSouth Pacific Cruise to TotalityDec. 5–19, 2020Enjoy 15 days aboard the M/S Paul Gauguin discovering gems like Fakarava, Bora Bora, and Moorea. Argentina and Brazil Total Solar Eclipse TourDec. 6–18, 2020Luxuriate in three nights each in Rio de Janeiro, Iguazu Falls, and Buenos Aires. Wonders of Chile Total Solar Eclipse Tour Dec. 6–15, 2020Enjoy gazing at the spectacular southern deep-sky, see the ALMA Observatory, and tour Santiago.PDon’t miss one of the biggest years in astronomy!Other Celestial Highlights...For complete details and to book, go to: TravelQuestTours.comAstronomy Magazine and TravelQuest International PresentCosta Rica Southern Sky PartyFeb. 23–Mar. 1, 2020Enjoy private southern sky stargazing from Star Lodge, and views of the Carina Nebula, Southern Cross, and Omega Centauri. Wonders of Ethiopia Annular Solar Eclipse TourJune 7–23, 2020Experience a true celestial wonder, see Lalibela, discover East African tribal cultures, and explore the Great Rift Valley.

S EN E FOR T E UR OUSCIC H CIDiscoverDA Big Box of CuriousFeed your brain with the Space & Beyond Box! Our sister publication, Astronomy magazine, just kicked off a super-cool subscription program. Each quarter, an astro-themed box of products lands at your doorstep. Dig in!spaceandbeyondbox.comJANUARY/FEBRUARY 2020 DISCOVER. 7 CONNECT WITH USBECKY LANG Editor In ChiefDAN BISHOP Design DirectorEDITORIALGEMMA TARLACH Senior EditorBILL ANDREWS Senior Associate EditorELISA R. NECKAR Production EditorANNA FUNK Associate EditorALEX ORLANDO Assistant EditorJENNIFER WALTER Assistant EditorMCLEAN BENNETT Copy EditorHAILEY MCLAUGHLIN Editorial AssistantContributing EditorsBRIDGET ALEX, TIM FOLGER,JONATHON KEATS, LINDA MARSA,KENNETH MILLER, STEVE NADIS,JULIE REHMEYER, DARLENE CAVALIER (special projects)ARTLUANN WILLIAMS BELTER Contributing Design DirectorELIZABETH WEBER Contributing Design DirectorDISCOVERMAGAZINE.COMERIC BETZ Digital EditorNATHANIEL SCHARPING Associate EditorMEGAN SCHMIDT Digital Content CoordinatorContributorsERIK KLEMETTI, LESLIE NEMO,NEUROSKEPTIC, COREY S. POWELL,SCISTARTER, TOM YULSMANADVERTISINGSCOTT REDMOND Advertising Sales Director888 558 1544, ext. [email protected] Media Connections KRISTI RUMMEL Consulting and Media Sales 608 435 [email protected] DECARLI Marketing ArchitectBOB RATTNER Research MEDIADAN HICKEY Chief Executive OfficerCHRISTINE METCALF Senior Vice President, FinanceNICOLE MCGUIRE Senior Vice President, Consumer MarketingSTEPHEN C. GEORGE Vice President, ContentBRIAN J. SCHMIDT Vice President, OperationsSARAH A. HORNER Vice President, Human Resources DAVID T. SHERMAN Senior Director, Advertising Sales and EventsLIZ RUNYON Circulation DirectorMICHAEL SOLIDAY Director of Design & ProductionLISA A. BERGMAN Managing Design DirectorCATHY DANIELS New Business ManagerKATHY STEELE Retention ManagerKIM REDMOND Single Copy SpecialistSCIENCE GROUPBECKY LANG Executive EditorDAN BISHOP Design DirectorSUBSCRIPTIONSIn the U.S., $29.95 for one year; in Canada, $39.95 for one year (U.S. funds only), includes GST, BN 12271 3209RT; other foreign countries, $44.95 for one year (U.S. funds only). CUSTOMER SALES & SERVICE800 829 9132Outside the U.S. and Canada: 903 636 1125Customer Service: [email protected] EDITORIAL [email protected] 21027 Crossroads Circle, Waukesha, WI 53186For reprints, licensing, and permissions:PARS International at www.parsintl.comfacebook.com/DiscoverMagtwitter.com/DiscoverMagDiscoverMagazine.cominstagram.com/discover.magazineYour Curiosity FixIt starts in the early spring, as the snow begins to leave for good. Discover editors huddle every couple of weeks to talk over the hot science news and hash out which stories will be the top finds of the year.This year, by April, we figured we had our No. 1 contender: Astronomers, for the first time, had an image of a black hole. And it wasn’t like this was a black hole right in our neighborhood; it was 55 million light-years away. Getting this shot meant you needed a telescope the size of the planet — which is exactly what they used.Discoveries like these keep us curious, and it’s why we take the time to assess the broadest possible range of research over many months. Because it’s thrilling to gaze at an image of something so ridicu-lously far away. It’s just as important, and alarming, to see a photo of sled dogs racing across a melting Greenland ice sheet that’s turned into a giant puddle.This annual issue brings you closer to understanding gene therapy as it begins to land in clinics. It questions why CBD seems to be everywhere, and how 1 million plants and animals could be on the brink of extinction — the most ever in human history.If you’re curious about life on this planet — and off it — then this issue is for you. O «Becky Lang Editor in ChiefFeel free to send comments and questions to [email protected]’S NOTE

8DISCOVERMAGAZINE.COM50TopStoriesScience that redefined our world and changed our thinking.

EJANUARY/FEBRUARY 2020 DISCOVER. 9Humanity’s s First Look at a at a Black HoleBY KOREY HAYNESiThis spring, astronomers revealed the first image ever taken of a black hole, bringing a decades-long effort to a dramatic conclusion. The image offers humanity its first glimpse of the gas and debris that swirl around the object’s event horizon, the point beyond which material disap-pears forever. A staple of science fiction has finally become visibly real.“We are delighted to be able to report to you today that we have seen what we thought was unseeable,” said Event Horizon Telescope (EHT) founding director Shep Doeleman when he announced the finding in April. The team of scien-tists made their announcement simultaneously in seven different countries, accompanied by a series of scientific papers published at the same time in The Astrophysical Journal Letters.The subject of the photo session was a nearby galaxy, dubbed M87, and its supermassive black hole, which packs the mass of 6.5 billion suns. Despite its size, the black hole is so far from Earth — 55 million light-years — that capturing the image required a telescope the size of our planet. The EHT fit the bill, with its network of nearly a dozen independent observatories across the globe, cooperating as one enormous detector. (Just eight observatories were part of the EHT in 2017, when researchers first gathered the image data.) The sci-entists then spent two years analyzing and format-ting it before they could unveil the finished picture. A photo of a black hole, at first, seems impos-sible. The objects are so massive and dense that not even light can escape their pull. That means a black hole is literally black — it neither gives off nor reflects any light. And, sure enough, at the center of the EHT’s image is the dark blob of the black hole itself, which astronomers often call its shadow. But the photo shows more than that: Surrounding the shadow is a bright, fiery ring of light.Feryal Özel is an astrophysicist at the University of Arizona and an EHT collaborator. She says that the light comes from hot gas swirling nearby, heated up during its violent descent into the black hole. “Our telescopes are able to pick up the light 1The first image of a black hole: the picture worth a thousand words — plus two years of crunching massive amounts of data.

10DISCOVERMAGAZINE.COMMAP: RETO STÖCKLI, NASA EARTH OBSERVATORY. INSETS, CLOCKWISE FROM TOP: GOPAL NARAYANAN; NIMESH PATEL; EWAN O’SULLIVAN; DANIEL LUONG-VAN; IZTOK BONCINA/ESO; ALMA (ESO/NAOJ/NRAO), C. PADILLA; SEAN GOEBEL; JOINT ASTRONOMY CENTRE; UNIVERSITY OF ARIZONA/DAVID HARVEYas long as it comes not from the immediate vicinity of the black hole, but just outside it,” Özel says. “When the light falls into the event horizon, that part is dark.”YEARS OF STITCHING TOGETHER DATAThe image, and resulting data, has helped astronomers learn more about black holes in general, and this one in particular, making that two-year wait more than worthwhile. Part of the reason for the delay was simply the logistics of gathering so many observations. Each observatory collects data over a narrow range of wavelengths, resulting in massive amounts of information — the equivalent of up to 5,000 years of mp3 music files. That’s too much to just email someone. Researchers instead had to find ways to physically move that data around. For instance, to transport the information out of the South Pole Telescope in Antarctica, scientists had to wait until spring, when planes finally started flying out again. Only then could researchers begin the complicated process of stitching together data from the eight observatories, a technique known as interferometry. The team had their work cut out for them: Raw files from each of the observing sites came in with different angles on the sky, in different wavelengths and at dif-ferent observation times.“The calibrating and working with it took many months,” Özel Hey, Black Hole,Say ‘Cheese’!How do you capture a close-up of a black hole? Start with a planet-sized telescope: the EHT. Astronomers at eight sites on four continents (a ninth, in Greenland, joined in 2018) collaborated to collect data and process it into a single image.SMASubmillimeter Arrayon Mauna Kea, HawaiiAPEX Atacama Pathfinder EXperimenton the Chajnantor plain of ChileALMA Atacama Large Millimeter/ submillimeter Arrayon the Chajnantor plain of ChileARO/SMT Arizona Radio Observatory’s Submillimeter Telescopenear Safford, ArizonaLMTLarge Millimeter Telescope “Alfonso Serrano”on Sierra Negra, MexicoSMAJCMTJCMTJames Clerk Maxwell Telescopeon Mauna Kea, Hawaii

JANUARY/FEBRUARY 2020 DISCOVER. 11says. “And at the end we synthesize it into a single image.” But that’s still not the end of the work, she says. “[You] spend another six months worrying about all the things you might have done wrong, and ask yourself more and more questions, until finally you can be certain that what you have is real.”TARGETING OUR GALAXY’S BLACK HOLEAnd that real image is just the first that astronomers expect the EHT will produce. The global array’s other main target is the black hole at the center of the Milky Way, Sagittarius A* (pro-nounced A-star). While it sits 1,000 times closer than M87, it’s also roughly 1,000 times smaller, so it takes the same amount of observing power. But because it’s smaller, the material swirling around its event horizon moves much faster, completing one circuit every few minutes; for M87, it’s once every few days. “It makes Sagittarius A* harder,” Özel says.What’s more, astronomers aiming at Sagittarius A* must look through the disk of the galaxy, which means dealing with more dust and other interfering material. But they still expect to release images of our galaxy’s black hole in the near future.Even more exciting are the repeat images of M87 and other black holes yet to come. By watching how the black hole does or doesn’t change with time, astronomers can learn about its stable features and watch how material disappears past the event horizon.SPTSouth Pole TelescopeSouth Pole Station, AntarcticaPVIRAM 30-Meter Telescope on Pico Veleta, SpainGLTGreenland Telescopeat Thule Air Base, GreenlandGLTSMTLMTAPEXALMASPTPV

12DISCOVERMAGAZINE.COMiAfter years of ethical debates and breakthroughs in the lab, CRISPR has finally made its way to clinical trials. Researchers are now looking at whether the DNA-editing tool, as well as more conventional gene therapies, can effectively treat a wide array of heritable disorders and even cancers. “There’s been a convergence of the sci-ence getting better, the manufacturing getting much better, and money being available for these kinds of studies,” says Cynthia Dunbar, a senior investigator at the National Heart, Lung, and Blood Institute. “It’s truly come of age.”CRISPR-ING OUT DISEASECRISPR — formally known as CRISPR-Cas9 — has been touted as an improve-ment over conventional gene therapy because of its potential precision. CRISPR (clustered regularly interspaced short palindromic repeats) is a genetic code that, contained in a strand of RNA and paired with the enzyme Cas9, acts like molecular scissors that can target and snip out specific genes. Add a template for a healthy gene, and CRISPR’s cut can allow the cell to replace a defective gene with a healthy one.In April, scientists at the University of Pennsylvania announced they had begun using CRISPR for cancer treatments. The first two patients — one with multiple myeloma, the other with sarcoma — had cells from their immune systems removed. Researchers used CRISPR to genetically edit the cells in the lab, and then returned them back into their bodies.Gene Therapy Gets ClinicalBY LINDA MARSA2

JANUARY/FEBRUARY 2020 DISCOVER. 13FOn the other side of the country, Mark Walters, a blood and bone marrow transplant specialist at the University of California, San Francisco, Benioff Children’s Hospital in Oakland, is gear-ing up for trials that will use CRISPR to repair the defective gene that causes sickle cell disease. “With CRISPR, once you’ve made that type of correction, [that cell] is 100 percent healthy,” says Walters.Another team is tackling the same disease using a type of hemoglobin, a protein in red blood cells, that’s nor-mally made only in fetuses and newborn babies. Researchers found that some adults continue to produce these pro-teins throughout their lives, and when those adults also have sickle cell disease, their symptoms are mild. So the interna-tional team used CRISPR to disable the gene that interferes with production of this hemoglobin, resuming its produc-tion and protecting the adult patients against sickle cell disease.Several other CRISPR studies are in the works to treat a range of inherited disorders, including hemophilia and SCID-X1 (also known as X-linked severe combined immunodeficiency, the so-called “bubble boy” disease in which babies are born without a functioning immune system).GENE THERAPY WITHOUT CRISPRThe past year also saw success in a hand-ful of experiments on conventional gene therapy. Instead of using CRISPR to repair disease-causing genes, these treatments use hollowed-out viruses to ferry healthy versions of genes into cells. Millions of these altered cells are released into the bloodstream or bone marrow in hopes that enough will land in the right places. But because scientists can’t predict where the circulating genes may end up, this shotgun approach has had unin-tended, sometimes fatal, consequences — including, in an earlier study, inadver-tently activating leukemia-causing genes in patients treated for SCID-X1. But in 2019, researchers learned that using a different type of virus — one related to HIV — to transport the genes may prevent these side effects. In an April study, researchers at St. Jude Children’s Research Hospital in Memphis, Tennessee, and UCSF Benioff Children’s Hospital in Oakland collected bone marrow from eight newborns with SCID-X1. They loaded corrective genes into the disabled HIV-related virus, which carried them into the patients’ bone marrow stem cells. The infants also received low doses of busulfan, a chemotherapy that gave the doctored stem cells room to grow. “So far, we haven’t seen anything worrisome,” says Ewelina Mamcarz, a pediatric oncologist at St. Jude who led the research team. The study recently added its 12th patient.“Gene therapy does have its momentum [back],” says Mamcarz, reflecting on the field’s setback after the earlier study’s leukemia side effects. “There’s so much that still needs to be done, and so many questions,” she says. “[But] this is how medicine evolves. We always want to be better than we were a week ago.” In the future, the hope is that gene therapy technologies will move beyond mending simple genetic mistakes and be used to combat big killers like dia-betes or heart disease. “[Those diseases are] more challenging, but a lot of them would benefit from knocking out a bad gene,” says Dunbar. For now, though, researchers are opti-mistic about the progress that’s already been made. “All of this has been very encouraging,” says Dunbar. “[And] for sickle cell in the U.S. and hemophilia in the developed world, these diseases may soon be solved.”Turn the page to read about competition for CRISPR: a new gene-editing tool.Early clinical trials brought promising results in 2019. At St. Jude Children’s Research Hospital, a gene therapy trial cured Gael Jesus Pino Alva (pictured with his mother, Giannina) of SCID-X1, the “bubble boy” disease.Gene therapy clinical trials are underway at places like UCSF Benioff Children’s Hospital in Oakland.

14DISCOVERMAGAZINE.COMMiFrom crash landings to out-of-this-world cotton, 2019 was a big year for lunar exploration. Previously, only the U.S., Russia and China had managed to land successfully on the moon. But now other national space agencies are charging ahead with their own science goals, and private companies of all sizes are finding ways to join in. Not to be left out, NASA is renewing its own plans for lunar exploration. The result has been a year of lunar successes and failures — and lots of big talk — with final outcomes still very much up in the air.It’s Prime Time for a New Gene EditoriCRISPR may have generated a lot of buzz this year, but some researchers are already looking beyond it to the next new gene-editing technique. Say hello to prime editing. “If CRISPR is like scissors … then you can think of prime editors like word processors,” said chemist David Liu in an October press briefing. He spoke days ahead of the first-ever prime editing study, published in Nature and authored by Liu and his team at the Broad Institute of MIT and Harvard University. Liu explained that, while CRISPR cuts through DNA’s double helix to snip out genes, prime editing searches for and replaces targeted genes without such slicing and dicing, reducing the risk of unintended changes to the genetic code.The team was able to correct mutations associated with both sickle cell and Tay-Sachs diseases. Liu believes the technique ultimately might be able to correct almost 90 percent of such mutations, but stressed additional studies are needed to gauge prime editing’s full potential. “This is the begin-ning, rather than the end,” said Liu. – Alex OrlandoIsrael Shoots for the MoonThe lunar lander Beresheet made history this year, thoughnot exactly how its creators intended. Israeli nonprofitSpaceIL, teaming up with state-owned defense company IsraelAerospace Industries, built and operated the craft. SpaceIL was founded for one main purpose: getting to the moon. It was a response toGoogle’s Lunar XPRIZE, which in 2007 promised $20 million to a company that couldland gently on the moon and complete a small series of tasks. No team had claimed the prize by the time it expired, after repeated extensions, in 2018.The Beresheet mission continued anyway, launching Feb. 22 on a Falcon 9 rocketmade by U.S. company SpaceX. It entered lunar orbit on April 4, making it the firstprivately funded spacecraft — and Israel the seventh nation — to orbit the moon. But on April 11, as Beresheet approached the surface, a faulty response to a minor sensor failure triggered an engine shutdown. Mission control managed to restart the engine, but by that point it was moving too fast to avoid a crash. When missioncontrol lost contact with the spacecraft, it was less than 500 feet from the surface, and moving at more than 300 mph. (Wiredd reported in August that the crash landing may also have introduced tardigrades — hardy life-forms that can survive incredibly harsh conditions — onto the lunar surface. Their fate remains unknown.)3 Race for the MoonBY KOREY HAYNES continued from previous page

JANUARY/FEBRUARY 2020 DISCOVER. 15China Explores the Lunar Far SideChinese state media announced thesuccessful landing of the Chang’e-4 mission on Jan. 3. It’s the first craft toland on the far side of the moon. The spacecraft touched down in Von Kármán crater, which is inside an even larger crater — the moon’s biggest, the South Pole-Aitken (SPA) Basin. Only 12 hours after arriving, Chang’e-4 released its rover,Yutu-2, to begin exploring the surrounding area.The lander carried a biosphere, a canister about the length and width of a human hand, containing a variety of plant seeds and insect eggs. While pictures sent to Earth showed cottonseed plants successfully sprouting, the containerapparently failed to warm properly against the frigid lunar night, and the experiment died after just nine days, instead of the planned 100.The rest of the mission has proceeded smoothly. The rover outlived its planned three-month lifespan, and the lander looks set to finish out its yearlong mission. Bothare continuing to take plenty of pictures,and are also probing the ground with radar and other tools to analyzethe interaction of the lunarsurface with the sun’s output. And in May, scientistsannounced that Chang’e-4 may have discoveredrocks originating deepbelow the moon’ssurface, in the lunar mantle, which wouldconfirm a longstandingtheory: The impact thatcreated the SPA basinstruck hard enough to punch through our satellite’s crust into the liquid mantle below.India Almost Returns tothe MoonOn July 22, theIndian Space ResearchOrganisation (ISRO) launched its second lunar mission, Chandrayaan-2. Chandrayaan-1 explored the moon in 2008, sending down an impactor to crash on the lunar south pole and fling up dust for investigation.As a follow-up, Chandrayaan-2 wasdesigned to map and study the geology of the moon’s south pole. But, to the dismayof scientists, the Vikram lander and itsrover, Pragyan, were damaged in a rough landing on the lunar surface in early September.Vikram and Pragyan were scheduled to reach the moon Sept. 6, but the crew lost contact as the spacecraft descended into the lunar atmosphere. They learned a day later that the spacecraft had crash-landed. ISRO attempted to establish contact with the lander and its rover, to no avail. The crew believes that errors in the automatic landing programming led to the mission’s downfall, according to reports by theTimes of India.Vikram and Pragyan were designed to explore farther south than any previousmoon missions. Their success would have made India the fourth nation to soft-landon the lunar surface, the same accolade Israel narrowly missed out on earlier in the year. But for now, it seems those milestones may be many moons away.

16DISCOVERMAGAZINE.COMFThe Private SectorStakes a ClaimPrivate companies have also made bold claims for the moon this year, though aside from Israel’s nonprofit SpaceIL,none has managed to get there.SpaceX has been working on its Starship vehicle as a means to reach Mars for years now. In July, SpaceX CEOElon Musk claimed that he could land an uncrewed ship on the moon in less than two years, and a crewed ship within four.The first major tests of Starship — usinga prototype called Starhopper (below)— have already begun. One of the tests,a tethered launch on July 16 that was literally connected to the ground, ended with the craft engulfed in flames, though it did survive. It went on to successfullycomplete an untethered “hop” on July 25. Further tests are proceeding. Meanwhile, Blue Origin founder andAmazon owner Jeff Bezos unveiled in Maythe Blue Moon lander, a spacecraft that can deliver up to 7 tons of cargo — andpossibly crew — to the lunar surface.Along with Blue Moon itself, the company revealed a new BE-7 rocket, which Bezos says has been in development for three years. Blue Origin began test-firing therocket for the first time this summer, andmore tests are underway. Together, Bezos says, these developments are a wayto return humans to the moon’s surface — “this time to stay.”It’s a bold claim for a spacecraft company that’s only reachedthe edge of space— and never fullyorbited. But bothprivate companiesare working to push the limits of humanspaceflight, and to keep NASA on its toes. NASA’s Lunar PlansPromiseMuch,Deliver LittleNASA’s own lunar plans have been no more certain this year. Theagency hasn’t put humans on the moon since 1972, and had recently focused on Mars as the next big destination, with the moon serving as a pit stop. But in March,Vice President Mike Pence changed thoseplans, instead calling for Americans — and the first woman — to walk on the moon by 2024. NASA Administrator Jim Bridenstine has estimated the cost of thenew program — dubbed Artemis, after thelunar goddess and twin sister of Apollo — at $20 billion to $30 billion. In July, NASA pushed ahead with a successful safety test of its Orioncrew capsule — a project already in development — and later that monthPence announced that it was ready for flight. The plan is for an uncrewed launch to take place after June 2020, with the firsthuman-led flight happening in 2022.NASA has maintained this accelerated timeline in spite of missed deadlines by Boeing, which was contracted to build the mighty Space Launch System rocket that will carry the Orion capsule into space.Pence and Bridenstine have talked a biggame, but it’s unclear how they will meet these looming goals if Boeing continues tofall behind.In the meantime, NASA has called for, and approved, a series of small science and technology demonstrations as part of its Commercial Lunar Payload Servicesprogram. The agency hopes these cargomissions to the lunar surface will startlaunching on small, private rockets before the end of 2019 — another goal that sounds less like a realistic deadline, and more like wishful thinking. Jennifer Walterrr, an assistant editor at Discover, contributed to this story package.

RJANUARY/FEBRUARY 2020 DISCOVER. 17iOne million species face extinction, more than ever before in human history, according to a U.N. report released in May. And humanity is responsible.The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) based the assessment on some 15,000 sources that consider the causes and consequences of environmental changes over the past 50 years.The findings are stark. The authors found that about 25 percent of the world’s plants and animals are vulnerable to extinction. These include over a third of marine mammals and more than 40 percent of amphibians. Even domesticated animals are at risk: Over 9 percent of domesticated mammal breeds used for food and agriculture already may have been lost. This rapid decline of the natural world endangers global food security and quality of life. For instance, an estimated 4 billion people rely on natural medicines, produced by the vanishing species, for their health care. And losses of species that pollinate plants would threaten up to $577 billion in crops each year.The researchers identified five drivers responsible for the grim news. At the top of the list is land- and sea-use change: the conversion of ecosystems to agriculture, aquaculture and other human developments. It’s followed by the direct exploitation of organisms (overharvesting, logging, hunting and fishing) and climate change, including rising sea levels and increasing extreme-weather events, wildfires, floods and droughts. The final culprits are pollution — especially plastics — and the spread of invasive species, non-native organisms that can displace or kill native plants and animals.The authors say only “transformative change” — such as a new global approach toward consumption and waste — could turn the tables. Whether that’s possible is an open question.A Million Species in DangerBY RONI DENGLER4Many sea turtle species worldwide are threatened with extinction, but the hawksbill sea turtle is the closest to the brink, followed by its relative, the Kemp’s ridley sea turtle. The hawksbill grows slowly, breeds rarely and is exploited by humans, which has led to its demise.

18DISCOVERMAGAZINE.COMTiSince 2008, when their fragmentary fossils first turned up in a Siberian cave, the Denisovans have been the most mysterious branch of the human family tree. The archaic humans, like Neanderthals, lived at the same time as early Homo sapiens but have been extinct for tens of thousands of years. For nearly a decade, we’ve known Denisovans from only one site, which yielded just a shard of finger bone and a few teeth from four individuals — and ancient DNA extracted from the scant remains.In 2019, however, a series of discov-eries revealed our evolutionary kin in greater detail than ever, answering some questions but also presenting new mysteries. One thing is clear: The Denisovans were much more complex than we thought, occupying diverse and sometimes extreme environments spread over much of Asia.In March, researchers announced that they had found two small skull fragments — the first known pieces of a Denisovan braincase — belonging to a fifth individual in Denisova Cave, in the Altai Mountains of southern Siberia. However, the biggest news about our mysterious extinct cousins came from outside their namesake cave.THE HIGH LIFEWriting in Nature in May, a separate team announced that a partial mandible, or jawbone, found in a cave on the Tibetan Plateau, came from a Denisovan. It was the first time a Denisovan had been found outside Denisova Cave. And, at around 160,000 years old and about 2 miles above sea level, it revealed that archaic humans lived at extreme altitudes long before our own species did.The discovery also cleared up a mod-ern mystery. Scientists have known that modern-day Tibetans possess a gene inherited from Denisovans thousands of years ago, when our species inter-bred. The gene, known as EPAS1, alters the body’s production of hemoglobin, a protein in red blood cells that car-ries oxygen, and helps them survive high-altitude environments. However, because Denisova Cave is not at high altitude, researchers had puzzled over why individuals living there would be adapted for the high life.Decoding the DenisovansBY NATHANIEL SCHARPING

JANUARY/FEBRUARY 2020 DISCOVER. 19The discovery of the Tibetan mandible solves that mystery, and also expands the known Denisovan territory by more than a thousand miles.The Tibetan jawbone might answer a few more questions, too. Scientists have not been able to identify a number of ancient human bones unearthed in China; knowing what Denisovan jaws look like may help them classify some of the undescribed fossils.MORE THAN THISWhile Denisovan fossils have been few and fragmentary, science has something just as valuable: their DNA. The first Denisovan genome was published in 2010, concurrently with news of their discovery, and it’s allowed scientists to probe their history from another angle altogether. Multiple research teams have recently compared the Denisovan genome with those of modern humans, turning up connections such as the Tibetan EPAS1 gene. Other studies have revealed that people in Southeast Asia and Oceania have a small percentage of different Denisovan genetic signatures.In April in the journal Cell, research-ers described a new wrinkle in the Denisovan story. By scanning the genomes of 161 people living in Indonesia and Papua New Guinea, the scientists isolated surviving fragments of Denisovan DNA in modern humans. The team says it found strong indica-tions that what we call the Denisovans might actually have been three distinct lineages of archaic human, spread from Siberia to Southeast Asia. They found the signatures of two separate Denisovan populations in the DNA from people in Indonesia and Papua New Guinea — and both differed from the Siberian Denisovans. One of those groups looked as different from Denisovans as from Neanderthals, which suggests it may have been a separate species.“If we’re going to call Neanderthals and Denisovans by a unique name, which we do, then we should probably call this other group by another name,” says paper coauthor Murray Cox, of New Zealand’s Massey University.Denisova Cave, Russia(Fossils discovered 2008)The Denisovan Range ExpandsFound in Baishiya Cave, high on the Tibetan Plateau (far left), a partial jaw (above; digital reconstruction, left) is the first Denisovan fossil found outside Russia’s Denisova Cave. Researchers continue exploring Baishiya (right) for additional evidence of the mysterious lineage of ancient humans. Baishiya Cave, China (Fossil confirmed 2019)Papua New GuineaIndonesia(Multiple Denisovan lineages confirmed 2019)

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AJANUARY/FEBRUARY 2020 DISCOVER. 21iNo single compound expanded its market in 2019 quite like CBD did. This cannabinoid owns the year’s bragging rights for new-product diversity, after find-ing its way into water, lattes, jellybeans, hummus, cosmetics and even doggie treats.CBD, or cannabidiol, is one of dozens of biologically active ingredients called cannabinoids created by Cannabis sativa plants. CBD only recently earned the most-popular-cannabinoid title — for decades, the crown more likely belonged to THC, the euphoria-inducing compound in marijuana. But not all C. sativa plants contain much THC: Those that do are considered marijuana, while those that don’t are called hemp. Now, the Farm Bill of 2018 has made growing hemp as mainstream as farming corn and soybeans, as long as derivative products contain no more than 0.3 percent THC. The bill also spells out federal regulations on cultivating and producing hemp. And more hemp means more CBD.Currently, the only FDA-approved CBD-based drug is Epidiolex, which treats seizures from rare types of epilepsy. A study published in May found that synthetic versions of CBD may also work on seizures, based on preliminary studies in rats. What’s more, researchers announced in June that CBD might even work as an antibiotic.But these results are still preliminary. The FDA has not approved any uses of CBD in food, beverages or dietary sup-plements — meaning it’s currently illegal for any companies to claim CBD has medical or therapeutic benefits. Outside of these uses, CBD is not federally regulated, so products available to the public can be all over the place in their claims. In September, the Federal Trade Commission sent letters to three companies selling CBD-infused products including oils, capsules and gummies, warning them it was illegal to make health claims without “competent and reliable” evidence.Despite the lack of proof, some people are turning to CBD as a way to self-treat symptoms like anxiety and pain, some-times as an alternative to opioids. In 2019, big-name stores like Sephora, Walgreens and CVS started selling products containing CBD, and celebrities started announcing product endorsements. “CBD is perceived as safe and attractive and is gaining widespread use,” says Simon Haroutounian, chief of clinical pain research at the Washington University Pain Center in St. Louis. But even though the market is booming, the quality of human research is spotty, he says. Researchers still don’t know how CBD works in terms of enzymatic pathways — that is, how the body eliminates CBD after intake. CBD is probably broken down in the liver, says Haroutounian, but until researchers know which enzymes are involved, they don’t know how CBD interacts with other drugs.It’s also unclear how much CBD reaches the blood after it’s inhaled or taken orally, and whether enough reaches target tissues. And researchers still don’t have reliable data on how often to administer CBD, or in what doses.“We are not in a very good position to make claims,” Haroutounian says. “We don’t even know what to tell people about driving impairment, whether they should avoid driving after ingesting a particular amount of CBD.”Although some data support claims that CBD doesn’t pro-duce the euphoria associated with THC, it’s still psychoactive, says forensic toxicologist Michelle Peace. “By some accounts, CBD relieves anxiety and PTSD symptoms, which means that it has a psychoactive effect,” she says.If CBD relaxes users, or makes them drowsy, she adds, such effects can impair driving, similar to a sleeping medication that would impair the ability to operate a vehicle.SKETCHY SMOKING SICKNESSAs of Oct. 15, the Centers for Disease Control and Prevention had reported over 1,500 cases — 33 of them deaths — across 49 states and the U.S. Virgin Islands of a lung illness associated The CBD Cure-All?BY JEANNE ERDMANNESSAYcontinued on next page

22DISCOVERMAGAZINE.COMwith vaping. As of this writing, the cause of the ill-nesses is still unknown, but could be linked to the nicotine, THC, CBD or any of the other additives found in e-cigarette products. It’s not the first time people have fallen sick after vaping. The CDC tracked an outbreak of poisonings in Utah in 2017 and 2018 from a fake CBD product that sent people to the ER with symptoms including confusion, hallucinations and seizures. Most of those poisoned had vaped the product.Peace had already been testing vaping prod-ucts when someone contacted her after having a bad experience vaping CBD oil. He ended up with a high he hadn’t wanted or anticipated. In work published in January in Forensic Science International, Peace and her team tested the CBD oil he had vaped, plus other products from the same company: They found the synthetic cannabinoid 5F-ADB and dextromethorphan, the active ingredient in cough syrup, either of which could be causing some of the reported side effects. In the same journal in April, a European team reported a case study of an 18-year-old man whose death was related to smoking synthetic cannabinoids, including 5F-ADB.“I think the tangle of these two industries has created some public health, public safety concerns,” says Peace, who is also a professor at Virginia Commonwealth University. Once her CBD vaping study came to light, people started contacting Peace to say they, too, thought they’d been poisoned by a CBD product. Peace and her team have been testing those products and calls some of the stories “pretty terrifying.” But answers and data are on the way. Peace and her team are preparing results of their 2019 follow-up studies for publication. In May, the FDA held a public hearing on the safety and effi-cacy of CBD products. In June, a bipartisan team of legislators introduced a bill aimed to stream-line research, and in September, the National Institutes of Health announced $3 million in new research awards to investigate the use of can-nabinoids and other cannabis-based, non-THC compounds for pain management. More than a hundred clinical trials are currently underway.“There are so many questions,” Haroutounian says. “We need to step back and do diligent work from square one.”Mini- Brains Make New Waves BY TEAL BURRELLiClumps of brain cells that are alive and practically kick-ing — that’s what scientists created when they tweaked a method for growing brain tissue in a dish. Meanwhile, another team used a different approach to produce brain waves in similar lab-grown mini-organs.The two papers, published in March in Nature Neuroscience and August in Cell Stem Cell, modified existing techniques for growing cultures called brain organoids. In organoids, human stem cells are first coaxed into becoming brain cells, which then organize themselves into a three-dimensional structure similar to a developing brain.Until now, one limitation of organoids was a lack of blood vessels. This meant cells in the middle of the pencil-eraser-sized blob died without access to oxygen and nutrients.But Madeline Lancaster, a developmental biologist at Cambridge University’s Medical Research Council Laboratory of Molecular Biology, and the Nature Neuroscience paper’s senior author, had an idea: “Why don’t we just cut them open?” By making thin slices separated by a membrane, the entire organoid could be exposed to oxygen and nutrients. “Developing brain tissue is quite happy like that,” she says.The cells not only stayed alive and healthy, they also formed neural circuits like they would in a developing embryo. Two weeks after the spinal cord and adjoining muscles of a mouse embryo were placed alongside the organoid, the muscles started moving, indicating functional connections grew between the organoid and spinal cord. Lancaster jumped when she first saw the movement. “The individual muscle units have to contract in a coordinated fashion in order for the whole muscle to move,” says Lancaster. “To see that actually happening in a dish, that blew me away.”The scientists behind the Cell Stem Cell paper took a different route: They spent four years optimizing the concentration and administration of proteins that would help the brain cells grow. Then they grew the organoids on top of electrodes, hoping the continued from previous page7

MJANUARY/FEBRUARY 2020 DISCOVER. 23perfected protocol would allow neurons to form networks with detectable electrical activity, like real brains. After four months of effort, that electrical activity began to increase exponentially. By nine months, it was 100,000 times higher than anything ever recorded outside the body. Next, the team compared the patterns and complexity of the activity with data collected from age-matched preterm babies. By 25 weeks, a computer program struggled to distinguish the organoids’ data from the babies’ brain waves. Alysson Muotri, a biologist at University of California, San Diego, and senior author of the paper, was surprised organoids produced complex brain waves without a complete brain or input from the body. It’s as if they follow a script. “These early stages of human development are totally genetically encoded,” he says. “The brain knows what to do and the information is inside the cells.” Both groups see their new techniques as helpful lab tools to investigate diseases and treatments. Lancaster has her eye on conditions where connections are disrupted, such as spinal cord injury and amyotrophic lateral sclerosis, while Muotri wants to make organoids from the cells of people with epilepsy or autism spectrum disorder to study their altered brain waves.Now that the lab-grown neurons remain healthier for longer, Lancaster also hopes to examine later stages of brain develop-ment. Meanwhile, Muotri is already considering other tweaks. Asked if they can come closer to modeling a real brain in a dish, he says, “If you asked me five years ago, I would say it’s impossible. And now I would say it’s inevitable.”False-color images of brain organoids allow researchers to color code different cells and map their activity (left and top two images). In reality, the organoids are pale and pea-sized (above).

Exploring the Farthest World YetBY KOREY HAYNES244DISCOVERMAGAZINE.COMISCOVERMAGAZINE.COM2DNiOn New Year’s Day 2019, the far-flung New Horizons spacecraft, which visited Pluto in 2015, set a new record when it buzzed by the most distant object yet visited by humanity: a remote space rock nicknamed Ultima Thule. The object — officially dubbed 2014 MU 69— orbits the sun a whopping 4 billion miles from Earth, deep within the realm of frozen rocks called the Kuiper Belt. That distance meant it took more than six hours for the spacecraft’s signals — traveling at light-speed — to reach Earth. The delay will only increase as New Horizons continues speeding deeper into space at 9 miles per second. It won’t finish sending back data on the space rock until summer 2020. When the first images trickled in, they revealed Ultima Thule to be a snowman-shaped world. Since then, researchers have found it oddly flat — less a snowman and more like two conjoined pancakes poured too closely together in the pan. Its two lobes, now called Ultima and Thule, were likely separate bodies that collided gently in the distant past. The region around Ultima Thule was clear of any dust, moons or rings. Those facts, and the asteroid’s fairly uniform makeup, make scientists think it’s led a quiet life in the far reaches of the solar system.Astronomers often consider space rocks the building blocks of the solar system, since they’ve undergone fewer changes than the material in large, complex bodies like planets and moons. For researchers looking for a pristine example, lonely Ultima Thule may be exactly the right target.

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iScientists adding human brain genes to monkeys — it’s the kind of thing you’d see in a movie like Rise of the Planet of the Apes. But Chinese researchers have done just that, improv-ing the short-term memories of the monkeys in a study published in March in the Chinese journal National Science Review. While some experts downplayed the effects as minor, concerns linger over where the research may lead. The goal of the work, led by geneticist Bing Su of Kunming Institute of Zoology, was to investigate how a gene linked to brain size, MCPH1, might contribute to Researchers React to Human Genesin MonkeysBY TEAL BURRELL266DISCOVERMAGAZINE.COMISCOVERMAGAZINE.COMMD2D

the evolution of the organ in humans. All primates have some variation of this gene. However, compared with other primates, our brains are larger, more advanced and slower to develop; the researchers wondered whether differences that evolved in the human version of MCPH1 might explain our more complex brains.Su and his team injected 11 rhesus macaque embryos with a virus carrying the human version of MCPH1. The brains of the transgenic monkeys — those with the human gene — developed at a slower pace, akin to that of a human, than those in transgene-free monkeys. And by the time they were 2 to 3 years old, the transgenic monkeys performed better and answered faster on short-term mem-ory tests involving matching colors and shapes. However, there weren’t any differ-ences in brain size or any other behaviors. But the results aren’t what has the sci-entific community buzzing. Some indi-viduals question the ethics of inserting a human brain gene into a monkey — an action Rebecca Walker, a bioethicist at the University of North Carolina, argues could be the start of a slippery slope toward imbuing animals with human-like intelligence. In a 2010 paper, James Sikela, a geneticist at the University of Colorado School of Medicine, and coauthors asked whether a humanized monkey would fit into its society, or would live in inhumane conditions due to its altered genes. To justify the work, Su and his co- authors suggested that it could pro-vide insights into neurodegenerative and social disorders — but they don’t describe what those applications might be. “I don’t really see anything in the paper that would make me think that [the experiment] was necessarily a good idea,” says Walker. Su declined Discover’s request for comment, but said in an article for China Daily, “Scientists agree that mon-key models are at times irreplaceable for basic research, especially in study-ing human physiology, cognition and disease.” And in the research paper, the authors contend that the “relatively large phylogenetic distance (about 25 million years of divergence from humans) … alleviates ethical concerns.” (Rhesus macaques are less like humans in terms of social and cognitive capacities than primates such as chimpanzees, which are more closely related to us.) This greater evolutionary distance suggests it would be harder to wind up with a macaque that acts like a human.But that reasoning falls flat for Walker. “It doesn’t really matter when they became differentiated from humans on the phylogenetic tree,” she says. “They’re talking about improved short-term memory, which would be putting them sort of closer to us in terms of those cognitive abilities.” She thinks manipu-lating these skills makes the work ethi-cally dubious and requires stronger justification. “While monkeys and humans have similar genomes,” Su said in the China Daily article, “there are still tens of mil-lions of genetic differences. Changing one gene carefully designed for research will not result in drastic change.”Sikela agrees that such a change may be minor. Still, he wonders about the possibility of finding a gene with a large effect on cognition. “There’s some risky elements to going down this road,” he says. “One needs to think about the consequences of where this is leading and what’s the best way to study these kinds of questions.”Walker also worries about where this work leads. “Could we enhance human brains through these methods?” she asks. While she thinks we’re nowhere close to that yet, she notes that sci-ence can advance surprisingly quickly. For instance, CRISPR — the gene-editing technique that once seemed far removed from human research — was used in China to edit the genomes of twins in 2018. (See our No. 11 story of the year, page 32.)“It does feel worrisome to be doing this research in primates,” Walker says. “And then potentially thinking about how that could be used in humans.”“THERE’S SOME RISKY ELEMENTS TO GOINGDOWN THIS ROAD.ONE NEEDS TO THINK ABOUT THE CONSEQUENCES OFWHERE THIS IS LEADING.”— JAMES SIKELA,GENETICIST,UNIVERSITY OFCOLORADOJANUARY/FEBRUARY 2020 DISCOVERANUARY/FEBRUARY 2020 DISCOVER. . 27 27J

Wet PawsSled dogs wade through a melting ice sheet in Greenland as researchers from theDanish Meteorological Institute travel to retrieve equipment in June. Three monthsearlier, a team of scientists in Denmark, the U.K. and the U.S. had published a study inScience Advances, predicting that over 25 percent of global sea level rise is due to the Greenland Ice Sheet melting; and Greenland alone could contribute 13 inches to sealevel rise by the end of the century. Without substantial reductions in greenhouse gas emissions, the researchers project, the island’s ice will disappear entirely before theend of the millennium.iFrom Antarctica to Greenland to the Himalayas, study after study in 2019 reported the world’s ice is melting at an accelerated rate. New sci-entific innovations allowed researchers to better quantify mass ice losses, and their studies exposed startling trends. The new findings paint a troubling future for glaciers around the world: If current ice-loss rates continue, scientists predict the collapse of glaciers around the world before the end of the century.A Melting PlanetBY DANIEL BASTARDO BLANCOS28DISCOVERMAGAZINE.COM

Spy SatellitesRecently declassified images taken by U.S. Cold War spy satellites have proved surprisingly helpful to glaciologists. Photos like the one to the left, fromthe border of India and Nepal in December 1975, are a snapshot of the past extent of the Himalayan glaciers. In a June study in Science Advances,researchers used the multi-angle observations of these spy films to build a 3D model of the region inthe last quarter of the 20th century. Their analysisshows that the Himalayas have lost twice as much ice in the last two decades as they did between 1975 and 2000.Death of a GlacierWhat’s left of the first Icelandic glacier lost to climate change, pictured above in 2018, was commemorated in 2019 with a memorial plaque.Glaciologist Oddur Sigurðsson declared Okjökull a glacier-no-more back in 2014, when the ice became too thin for glacial movement. But it wasn’tuntil 2019 that members of the Icelandic Hiking Society, Rice Universityand the general public installed the monument at its former site. The August induction of the memorial followed the publication of an April Nature study that attributes 25 to 30 percent of the observed global mean sea level rise between 1993 and mid-2014 to glacier melting.FJANUARY/FEBRUARY 2020 DISCOVER. 29Plaque installed in August 2019 at the site of former glacier Okjökull. It reads: A letter to the futureOk is the first Icelandic glacier to lose its status as a glacier. In the next 200 years all our glaciers areexpected to follow the same path. This monument is to acknowledge that we know what is happening and what needs to be done. Only you know if we did it.August 2019415 ppm CO2

300DISCOVERMAGAZINE.COMISCOVERMAGAZINE.COMMovin’ on IceIce is always on the move. Knowing where — and how fast — it’s going is crucial for predicting ice sheet stability, which informs predictions about melt rates and sea levelrise. That’s why researchers in California have created the most precise map so far of Antarctica’s ice velocity, which they published in Geophysical Research Lettersin July. But that wasn’t the only Antarctic news in 2019. In a January study in theProceedings of the National Academy of Sciences, a different team found that the melting continent has contributed morethan half an inch to global sea levels in the past 40 years, and it’s now losing six timesmore ice annually than it did in 1979.3DFOver/UnderIce sheets like LeConte Glacier in Alaska (left)don’t just melt on their open-air surfaces; they canalso lose ice underwater. In a July Science paper,a group of researchers used a multibeam sonarsystem — the same technology anglers use to findlarge schools of fish in the ocean — to directlymeasure underwater melting rates for the first time.The innovative approach shows LeConte could be melting 100 times faster than previously estimatedby theoretical models, suggesting worldwide melt rates may be seriously underestimated.Ice, Ice, MeltyMelt season came early this year to Greenland’s Russell Glacier, researchers working on NASA’sOperation IceBridge noticed in May. And new research suggests that could become a common occurrence across Greenland. Normally, snowcovers and protects most of a massive ice sheetfrom the heat of the sun. But the snow ends atwhat’s called the snowline, leaving the bare ice exposed. A MarchScience Advances study pointedto changes in Greenland’s snowline as a factor accelerating ice loss in the region. Greenland’s snowline moved about 55 feet per year from 2001to 2012, exposing more ice to the sun’s melting rays.1000 kmIce velocity (m/yr)<1 10 1000 1000 >3000

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JANUARY/FEBRUARY 2020 DISCOVER. 33iOften, science moves ahead incrementally. Yet sometimes it advances in dramatic leaps and bounds that can stir new hopes for medical benefits while shaking society to its very core. We saw both in 2019, as work using the gene-editing tool CRISPR gained momentum. The year opened with the scientific community scrambling to respond to the news that Chinese researcher He Jiankui had used CRISPR technology to edit the genomes of human embryos. The experiments resulted in the November 2018 birth of twin girls, the first humans with genetically altered germline cells — which means their genetic changes are heritable and can be passed on to future generations. The National Institutes of Health (NIH), a crucial public sup-porter of biomedical research, is among the many who consider such experiments both irresponsible and unethical. The NIH has not funded any use of heritable gene-editing technologies in human embryos, and it has no intention of doing so. But NIH’s strong stance against heritable gene editing does not mean that we think CRISPR has no role in the future of clin-ical medicine. This innovative technology possesses enormous potential for therapeutic good if used for making nonheritable genetic changes. In that approach, genetic material is altered only in relevant somatic (nonreproductive) cells, so there is no chance of passing those changes on to future offspring. NIH’s highest priorities in 2019 included supporting research aimed at using nonheritable gene editing to help people with life-threatening disorders, such as sickle cell disease, HIV infection, cancer and muscular dystrophy. Indeed, such applications may offer the best hope not only for treating, but for curing, many of the nearly 6,000 human genetic diseases that still lack treatments.Now, scientists and leaders around the globe have an obliga-tion to consider the appropriate use — if any — of heritable human gene editing. This involves scrutinizing the safety of such experiments, including the risk of unintended mutations, as well as a clear-eyed analysis of actual medical need. In our view, the current arguments — that the benefits outweigh the risks — are surprisingly uncompelling. But our deliberations should not stop there. We must weigh the profound social, ethical and moral issues associated with modifying the germline in ways that could change the human species forever. Given the significance of these decisions, in March, lead-ing scientists from seven countries — led by Eric Lander and including CRISPR pioneers Feng Zhang and Emmanuelle Charpentier — called for a five-year international moratorium on the use of gene editing to modify the human germline for clinical purposes. The NIH supports such a moratorium.Despite the calls for caution, some researchers are forging ahead. In June, Russian molecular biologist Denis Rebrikov announced plans to implant gene-edited embryos into women. Like his Chinese counterpart, Rebrikov planned to use CRISPR to target the CCR5 gene to protect against HIV; he later changed course to focus on GJB2, a gene linked to heritable hearing loss. Direct editing of embryos is not the only way to alter the human germline in heritable ways: In August, New York-based reproductive biologist Gianpiero Palermo went public with his plans to use CRISPR technology to target a gene that increases cancer risk in human sperm. But such moves continued to meet vigorous opposition. In August, a number of research groups working on gene-editing therapeutics issued a statement asserting heritable gene editing is currently inappropriate for use in human clinical studies. That same month, a group of international research societies convened to discuss recommendations for appropriate research, which are slated for completion in spring of 2020. Meanwhile, the World Health Organization’s new expert advisory committee, convened in the wake of He’s experiments, sidestepped the issue of a moratorium at its August meeting. It did, however, establish a global registry to track all kinds of human gene-editing research and to offer consultation on governance of such technologies. A moratorium of at least five years on heritable human gene editing would provide us time to engage in proactive, rather than reactive, discussions about the future of such technology. That discussion has to be inclusive of many societal perspectives. We must never allow our technology to eclipse our humanity. As an interconnected global society, we have a responsibility to ask ourselves some very hard questions about heritable gene editing and the dangers of human hubris. While difficult, this is a debate that we simply cannot afford to postpone. Francis S. Collins is the director of the National Institutes of Health.The First Gene-Edited Babies Turn 1BY FRANCIS S. COLLINSESSAYC

12S34DISCOVERMAGAZINE.COMiSince the end of the space shuttle program in 2011, the U.S. has used Russian Soyuz spacecraft every time it wants to, well, shuttle humans to and from space. While NASA is busy work-ing on its own solution, the agency has increasingly turned to private companies, such as Elon Musk’s SpaceX, to cover its off-planet transportation needs. Although SpaceX has successfully flown cargo flights for NASA since 2012 via the reusable Dragon spacecraft, the company has yet to launch humans in its so-called Crew Dragon capsule. Originally promised to launch in 2017, the program has seen multiple delays. It is, after all, rocket sci-ence, and the path has not been easy. But this year seemed different. NASA’s pre-purchased Soyuz flights run out by the end of 2019, and SpaceX — along with Boeing — had scheduled all its final tests to achieve certification in time to pick up where Soyuz left off. On March 2, the Crew Dragon capsule launched on a dry run without crew toward the ISS. It docked, unloaded supplies and splashed back down in the Atlantic Ocean on March 8. The flight, known as Demo-1, went flawlessly. The Bumpy Roadto Launching a DragonBY KOREY HAYNES The SpaceX Crew Dragon docks at the International Space Station in this artist’s illustration. NASA, Boeing and SpaceX are partnering to build the spacecraft (opposite).

CiUntil recently, a lack of blood flow in the brain was thought to guarantee instant, irreversible death. But researchers reported in Nature in April that this may not always be the case, after they successfully resurrected the brains of pigs four hours after the animals had died.Scientists already knew it was possible to harvest cells from brains after death and keep them alive in petri dishes. “This indicated that cells in the postmortem brain may still have the capacity to be revived,” lead researcher and Yale School of Medicine neuroscientist Nenad Sestan explained during a press conference.The scientists removed the decapitated pigs’ brains and connected about 30 of them to a system of chambers, pumps and tubes. For six hours, the system, which they call BrainEx, pumped a solution of synthetic nutrients through the brains. The goal was to mimic the role living organs in the body normally play to sustain the brain.It worked: The system successfully restored some blood flow and cell activity to the deceased animals’ brains. The researchers note the brains were never alert or conscious. In addition to monitoring the electrical activity of individual cells, the scientists monitored the brains’ activity as a whole. The researchers found no evidence for higher-order brain activity or any indication the brains could perceive the environment or experience sensations.“This is not a living brain. But it is a cellularly active brain,” Sestan said. The researchers emphasized the goal of the research was never to bring about consciousness. In fact, they had steps in place to shut down the experiment had they discovered certain types of electrical signals that can be associated with consciousness. Instead, the researchers hope the work will lead to new ways to aid recovery after trauma such as heart attacks and strokes.The researchers received the heads of pigs that had been slaughtered at a Connecticut food-processing plant. Because the animals were bred and butchered as part of the food industry, they weren’t killed solely for research, the authors say.Brains Brought Back to LifeBY RONI DENGLER13 The next major milestone scheduled was the in-flight abort test, another uncrewed mission meant to test the reli-ability of the abort system that would save the crew in case of any mishap during launch. The plan was to use the same cap-sule from the Demo-1 flight. But SpaceX never got the chance. On April 20, the company ran what was supposed to be a routine test, firing certain rockets with the capsule anchored firmly to ground. Some 100 milliseconds before the engines fired, a leak of oxidizer into a pressurized helium line caused an explo-sion that completely destroyed the capsule. SpaceX spent the rest of spring and early summer figuring out what had gone wrong and scrambling to prep a replace-ment capsule. While the problem is now solved, and the replacement capsule should be ready by the end of the year, the in-flight abort test has yet to happen as of press time. The Demo-2 mission, the first to fly with actual humans on board, was set to launch no earlier than Nov. 15, but it’s doubtful that SpaceX will carry passengers before 2020.A new method restored some cellular function to pig brains (top) four hours after death. An untreated brain (middle) is dark compared with a treated brain (above), which shows significant neural (in green) and other electrical activity.

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JANUARY/FEBRUARY 2020 DISCOVER. 37FScott Maxwell, former Mars rover driver team lead“Put simply, I loved Opportunity, as I did her twin sister, Spirit. I was privileged to be part of a team that was ecstatically devoted to them for years. We sacrificed dinners with family, vacations, whole marriages to those rovers. And they were worth it: In exchange, they gave us a planet. They were our eyes and ears, our remote robot bodies.“The thought of saying good-bye to Opportunity fills me with mixed emotions: pride, certainly, at her enormous accomplish-ments, but grief and despair at her loss. And, truthfully, I think the pride will have to wait a while. There’s no room for it now.”Abby Fraeman, deputy project scientist, who first worked with the mission as a teenager“In terms of the science accom-plishments, Opportunity was the first rover to find definitive evidence for liquid water on the surface of Mars. We learned a lot about how to drive rovers on another planet using Opportunity.“Another legacy that I think is important from my personal story is the legacy of inspiration. I know I’m not the only one who has a story, who thinks that Spirit and Opportunity flipped a switch in their heads and said, ‘Oh my gosh, I’d love to pursue a career in math or in science to be able to do something like this for a career.’ I think that’s another important legacy that’s a little bit harder to quantify, but it’s just as important as the science results that have come out.”Keri Bean, science planner on Opportunity“I think Opportunity has made the solid case that, at least in some point in the past, Mars was habitable. We don’t know when, we don’t know if it ever happened, but at least there were several spots on Mars where we could have potentially had life, whether now or in the past, and I think that’s really fascinating.“For me personally, I think Opportunity has always just kind of persevered. Mars has thrown a heck of a lot at her. This isn’t even her first global dust storm. She’s survived so much. Parts have broken along the way. There’ve been problems along the way. Yet every single time, we’ve overcome it, and this is finally the one we can’t overcome. I wish she could have persevered a little longer, but Mars had other plans.”Tanya Harrison, science team collaborator“If I had the chance to say one last goodbye to Oppy, I would thank her for her tireless service above and beyond all possible expectations. There’s probably no more fitting way for her to have gone than in the strongest dust storm we’ve ever seen on Mars — for her, I would expect nothing less. Now she can rest beneath a thin layer of dust, knowing she did humanity proud.”Remembering the Opportunity RoverBY JOHN WENZiAfter some 15 prolific years on the martian surface, NASA’s Opportunity rover has gone silent. It took a whopping planet-wide dust storm to fell the solar-powered robot, but, in February, the space agency officially ended the mission. We talked with NASA scientists about their experiences working on the golf-cart-sized rover and what Opportunity meant to them. Their eulogies for the lost rover, originally intended to last just three months on Mars, are below.Intended to last just three months on Mars, Opportunity went the distance for about 15 years, providing invaluable data.

38DISCOVERMAGAZINE.COMJiIn February, a very real paper ran in Scientific Reports titled, “Human Mind Control of Rat Cyborg’s Continuous Locomotion with Wireless Brain-to-Brain Interface.” It described how existing technology — such as brain-brain interfaces (BBIs) and, incredibly, rat cyborgs — can work together to produce that eye-popping title.BBIs and brain-machine interfaces (BMIs) have already helped improve how people control prosthetics and other devices. But the technology can also function the other way around — instead of a brain controlling a device, a machine can alter brain patterns or “import tactile information back to the brain,” as the study’s authors put it. So, in effect, BMIs could allow for mechanically “controlling” others’ brains.Here’s how it works in practice: A human manipulator has movement-related thoughts, which a wearable EEG — a device that records brain wave patterns — picks up and transfers to a computer. The computer translates that signal into “control instructions” and wirelessly beams them into a receiver on the back of a rat. The receiver then sends them into the rat’s brain via pre-installed electrodes. And the rat responds to the instructions in its brain by actually doing them.“With this interface, our manipulators were able to mind con-trol a rat cyborg to smoothly complete maze navigation tasks,” the authors write. I know what you’re thinking (a chilling phrase given the context): Is this for real? “[The study] is for real, and I don’t see anything implau-sible about it,” says University of Washington brain researcher Andrea Stocco, who was not involved with the work. He sug-gests the tech could be useful for improving augmented reality systems or even helping an expert surgeon remotely control a local doctor’s hands in a delicate operation.But, he says, “the holy grail of BBI would be sharing rich con-tent that cannot be better expressed in words, such as emotions and feelings. We are still so far from that, but, of course, that would be the dream.”15Mind-Controlled Rats Are Now a ThingBY BILL ANDREWSHow to Tell a Rat Where to Go Source: Zhang, Shaomin, et al, Scientific Reports, 2019CameraAs a human watches the video, their movement-related thoughts provide direction.Thoughts are processed into microelectric instructions and sent to rat’s brain.Live video from the maze

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40DISCOVERMAGAZINE.COMLThe Rules of the Road to Quantum SupremacyBY STEPHEN ORNESLSU physicist Jonathan Dowling (right), shown with alumnus Todd Moulder, has pushed the growth rate in quantum computing.

Q A &JANUARY/FEBRUARY 2020 DISCOVER. 41The subtext: We are venturing into an age of quantum supremacy — the point at which quantum computers outper-form the best classical supercomputers in solving a well-defined problem.Engineers test the accuracy of quantum computing chips by using them to solve a problem, and then verifying the work with a classical machine. But in early 2019, that process became problematic, reported Neven, who runs Google’s Quantum Artificial Intelligence Lab. Google’s quantum chip was improving so quickly that his group had to commandeer increasingly large computers — and then clusters of computers — to check its work. It’s become clear that eventually, they’ll run out of machines. Case in point: Google announced in October that its 53-qubit quantum processor had needed only 200 seconds to complete a problem that would have required 10,000 years on a supercomputer.Neven’s group observed a “double expo-nential” growth rate in the chip’s comput-ing power over a few months. Plain old exponential growth is already really fast: It means that from one step to the next, the value of something multiplies. Bacterial growth can be exponential if the number of organisms doubles during an observed time interval. So can computing power of classical computers under Moore’s Law, the idea that it doubles roughly every year or two. But under double exponential growth, the exponents have exponents. That makes a world of difference: Instead of a progression from 2 to 4 to 8 to 16 to 32 bacteria, for example, a double-exponentially growing colony in the same time would grow from 2 to 4 to 16 to 256 to 65,536. Neven credits the growth rate to two factors: the predicted way that quantum computers improve on the compu-tational power of classical ones, and quick improvement of quantum chips themselves. Some began referring to this growth rate as “Neven’s Law.” Some theo-rists say such growth was unavoidable. We talked to Dowling (who suggests a more fitting moniker: the “Dowling-Neven Law”) about double exponential growth, his prediction and his under-appreciated Beer Theory of Quantum Mechanics. Q: You saw double exponential growth on the horizon long before it showed up in a lab. How?A: Anytime there’s a new technology, if it is worthwhile, eventually it kicks into exponential growth in something. We see this with the internet, we saw this with classical computers. You eventually hit a point where all of the engineers figure out how to make this work, miniaturize it and then you suddenly run into exponential growth in terms of the hardware. If it doesn’t happen, that hardware falls off the face of the Earth as a nonviable technology. Q: So you weren’t surprised to see Google’s chip improving so quickly?A: I’m only surprised that it happened earlier than I expected. In my book, I said within the next 50 to 80 years. I guessed a little too conservatively.Q: You’re a theoretical physicist. Are you typically conservative in your predictions?People say I’m fracking nuts when I publish this stuff. I like to think that I’m the crazy guy that always makes the least conservative prediction. I thought this was far-out wacky stuff, and I was making the most outrageous prediction. That’s why it’s taking everybody by surprise. Nobody expected double exponential growth in processing power to happen this soon.Q: Given that quantum chips are getting so fast, can I buy my own quantum computer now?A: Most of the people think the quantum computer is a solved problem. That we can just wait, and Google will sell you one that can do whatever you want. But no. We’re in the [prototype] era. The number of qubits is doubling every six months, but the qubits are not perfect. They fail a lot and have imperfections and so forth. But Intel and Google and IBM aren’t going to wait for perfect qubits. The people who made the [first computers] didn’t say, “We’re going to stop making bigger computers until we figure out how to make perfect vacuum tubes.”Q: What’s the big deal about doing problems with quantum mechanics instead of classical physics? A: If you have 32 qubits, it’s like you have 2 parallel universes that are working 32on parts of your computation. Or like you have a parallel processor with 2 32processors. But you only pay the electric bill in our universe. Q: Quantum mechanics gets really difficult, really fast. How do you deal with that?A: Everybody has their own interpretation of quantum mechanics. Mine is the Many Beers Interpretation of Quantum Mechanics. With no beer, quantum mechanics doesn’t make any sense. After one, two or three beers, it makes perfect sense. But once you get to six or 10, it doesn’t make any sense again. I’m on my first bottle, so I’m in the zone.NEVEN’S GROUP OBSERVED A “DOUBLE EXPONENTIAL” GROWTH RATE IN THE CHIP’S COMPUTING POWER OVER A FEW MONTHS.iIn his 2013 book, Schrödinger’s Killer App, Louisiana State University theo-retical physicist Jonathan Dowling predicted what he called “super exponen-tial growth.” He was right. Back in May, during Google’s Quantum Spring Symposium, computer engineer Hartmut Neven reported the company’s quantum computing chip had been gaining power at breakneck speed.

42DISCOVERMAGAZINE.COMiAt the northern tip of the Philippine island of Luzon lies Callao Cave, an expansive, seven-chamber limestone warren. In April, researchers reported in the journal Nature that they’d uncovered the bones of a now-extinct, previously unknown human species near the far end of the first chamber. The discovery adds to growing evidence that human evolu-tion and dispersal out of Africa is much more complicated than scientists once thought — and that we’re just starting to understand Southeast Asia’s role in that story.“There is no reason why archaeological research in the Philippines couldn’t dis-cover several species of hominin,” Philip Piper, an archaeologist at the Australian National University who coauthored the new research, said in a statement. “It’s probably just a matter of time.”In 2007, Piper and an international team of researchers discovered a foot bone in Callao Cave that belonged to a member of New Member of Our Family Tree Found in PhilippinesBY RONI DENGLERCRemains preserved in Callao Cave (top) include several teeth (above) with traits that established the individuals belonged to the genus Homo — but also raised questions about their evolution.

JANUARY/FEBRUARY 2020 DISCOVER. 43the genus Homo, though they were unable to determine which species.Researchers continued to excavate the cave, eventually unearthing more bones — plus seven teeth — from three individuals who lived at least 50,000 years ago. That date would mean they were alive at the same time as Neanderthals, Denisovans and our own species, as well as Homo flo-resiensis, short and small-brained ancient humans who lived in Indonesia.The Callao Cave bones have a unique combination of primitive and modern human traits, leading the researchers to classify them as an entirely new spe-cies: Homo luzonensis.The seven teeth found were of par-ticular interest to the researchers. Oddly small molars are similar in shape to those of H. sapiens. However, they also have features that resemble the molars of H. erectus, a much earlier human spe-cies that dispersed out of Africa about 2 million years ago. And parts of the pre-molars of H. luzonensis resemble those of H. floresiensis.Meanwhile, the curved shape of the toe and finger bones of H. luzonensis look like those of australopiths, human predeces-sors that lived some 3 million years ago. That means H. luzonensis likely spent some of its time climbing in trees — even though other Homo species were ground-dwellers by this point.The discovery of H. luzonensis on an island that was never connected to main-land Asia, and which would have required a significant sea crossing to reach, adds to the mystery surrounding the latest addi-tion to our family tree.FL18Editing Out HIVBY RONI DENGLER iNearly 37 million people have human immunodeficiency virus (HIV), the cause of AIDS. The go-to treatment for the infection, antiretroviral therapy (ART), can prevent the disease’s progression, allowing people to live longer and healthier lives. But even with ART, the virus still lingers in the body by copying itself into the DNA of infected cells.This year, researchers described a new form of ART which, in combina-tion with CRISPR gene editing, eradicated the virus during testing on mice — a big step toward new therapeutic avenues for HIV patients. To mimic a human infection in mice, the researchers used “humanized mice,” which make human immune cells, rather than mouse immune cells. These human cells are susceptible to HIV. When the team injected the mice with the virus, they saw the infection take up residence in the places it would in humans: in DNA in cells in the lymph nodes, spleen, liver, lungs and brain.The team used the mice to test a new, so-called “long-acting slow-effective release” (LASER) ART treatment. The therapy uses retroviral nanoparticles that take more time to dissolve and persist longer in the body, to prevent the virus from replicating. They found that LASER ART, administered every few weeks rather than daily, stopped 99 percent of the virus’ replication. But, as with standard ART, the new treatment could not remove any part of the virus that had already entered a patient’s DNA. So for the final punch, the researchers used CRISPR gene editing to cut out the virus’ DNA from the genomes of the infected mice. This eliminated all traces of HIV from more than 30 percent of the mice, the team reported in July in the journal Nature Communications. “Our findings show for the first time that HIV can be cured from an infected cell and the cell will remain virus-free,” said Temple University virologist Kamel Khalili, one of the senior investigators leading the research. He says the results show promise for moving ahead within a couple of years to trials in non-human primates and, eventually, to humans.Temple University virologist Kamel Khalili (front center) and a team of researchers showed that CRISPR gene-editing technology could help remove HIV from the cells of infected mice.Philip Piper

44DISCOVERMAGAZINE.COMELots o’ Motza!BY BRIDGET ALEXi Nine thousand years ago — a couple of millennia after the first humble farming villages appeared in the Middle East — Motza was a town ahead of its time, a vanguard of urban life. Home to thousands, the roughly 80-acre site was about 10 to 100 times larger than other settlements of the day.“Mega-huge,” says Hamoudi Khalaily, who co-led excavations at the site, which nestles between olive and dun-colored hills in present-day Israel. In July, after 16 months of digging, the Israel Antiquities Authority (IAA) team unveiled Motza’s grandeur. The town was a dense hub of workshops, public halls and private homes linked by roads and alleys. Evidence of art and trade was everywhere, including bountiful artifacts such as handcrafted jewelry, Red Sea shells and Anatolian volcanic glass. “You get the big full package, the big full town with all of those luxuries, orga-nized street systems, et cetera,” says Omry Barzilai, head of archaeological research at IAA.Also found were several hundred human burials beneath homes through-out the settlement, similar to other sites of the period.The town’s scale surprised even team members. Researchers had known some early farmers inhabited the area since scattered flint tools, distinctive of the era, surfaced in the 20th century. But they didn’t expect much: The region was thought to be mostly abandoned during this part of the Neolithic. The IAA only probed deeper because a highway was about to be built over Motza.Preliminary pits in 2015 confirmed buildings that were about 9,000 years old just a couple of feet below the surface. But it wasn’t until late 2018, eight months into full-scale excavations, that it became clear “we are dealing with one of the largest sites in the Middle East,” Khalaily says.

JANUARY/FEBRUARY 2020 DISCOVER. 45Usually, archaeologists just dig portions of a site, in order to leave remains for future researchers. But because Motza was des-tined for development, the team sought to excavate its entirety, resulting in a nearly complete picture of life in the New York City of the Neolithic. In excavation layers closer to the surface, the team found far fewer buildings and artifacts, suggesting the settlement peaked and then dwindled.Analysis of the finds will continue for years, potentially explaining what caused the mega-site to boom and fade. Barzilai hypothesizes population growth outpaced resources and social organization. “Maybe it was pushed to the limit,” he says.The Motza mega-site (left) is about 3 miles from Jerusalem. Stabilized by white sandbags, excavation squares contain stone walls and plaster floors, which reveal the ancient town’s architecture and roads. Urban planning and variable-sized homes suggest the presence of formal leaders and social strata.Archaeologists recovered thousands of flint tools crafted by early farmers, such as sickles to harvest crops and arrowheads (above) for hunting and warfare.Archaeologists (top) unearthed about 300 human burials under plaster floors, in courtyards and between walls. Skeletons (above) were curled on their sides, knees tightly tucked, suggesting the bodies had been bound. Some were missing heads. The skulls may have been removed and covered in plaster, as was the custom at other sites in the region.

46DISCOVERMAGAZINE.COMAMost Massive T. Rex Ever Died Old and Battle-WornBY GEMMA TARLACHi “It’s a big honkin’ animal.”That’s how College of Charleston paleontologist Scott Persons describes the fossil that happens to share his name. “Scotty,” named for a celebratory bottle of scotch cracked open to toast its discovery, is the biggest Tyrannosaurus rex in the fossil record — and the most elderly.The first bits of the animal surfaced back in 1991 in southwestern Saskatchewan, Canada, encased in iron-rich, extremely hard sandstone, which made excavation difficult and time-consuming. At the time, Persons notes, “no one knew how much of the animal was there, or how big it was.”It would take decades for researchers to excavate and prepare the bones for study. In fact, it wasn’t until March, when Persons and colleagues published the first full analysis of the animal in The Anatomical Record, that its enormity could be fully appreciated.At an estimated 19,500 pounds and with a length of nearly 43 feet, Scotty is kind of a big deal. It’s larger than the most famous tyrant king fossil, Sue, who currently resides at Chicago’s Field Museum. Sue is a couple feet shorter and about 800 pounds lighter.“You couldn’t say this thing rivals Sue until you had all the numbers,” says Persons. But he is quick to note that size isn’t everything when it comes to the mightiest of apex predators. Scotty is an impressive 65 percent complete, but, at about 90 percent, “Sue is still the most complete. To be fair, in terms of scientific value, that counts for more.”The most significant thing about Scotty may be its advanced age. Coauthor Gregory Erickson studied growth pat-terns preserved in Scotty’s bones, similar to tree rings, to determine the animal was more than 30 years old when it died some 66 million years ago. Says Persons: “Most T. rexes die when they’re teenagers.” (For comparison, paleontologists believe Sue lived to the ripe old age of 28.)“Scotty lived a hard-knock life,” Persons adds, naming a long list of animals, from club-tailed ankylosaurs to another hun-gry T. rex, that could have fought the apex predator. “Little kids tell me all the time they want to be a T. rex and I say, ‘No, no, no! T. rexes had an awful life!’ You’re trying to make a living and find your next meal and you’re getting beat up by everybody.”Scotty had the scars to prove that. The animal’s remains include a broken rib, a nasty, lingering infection in its jaw and a massive compression injury on its tail that may have been the result of chomping by another T. rex.While Persons is thrilled about present-ing his namesake to the world, he believes Scotty won’t hold the heavyweight cham-pion title for long.“I can guarantee you that, in generations to come, it won’t be the biggest,” he says. “T. rex was around for millions of years, [and] we probably haven’t found the full extent of the range. There’s no way that we’ve happened to stumble across the largest member of the species.”Paleontologist Scott Persons (above and top left, with “Scotty” — no relation) believes the 65-percent-complete tyrannosaur, the most elderly and the most massive in the fossil record, won’t be the biggest T. rex ever found.

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