Woolly mammoths died out about 3,000 years ago, ending 100,000 years or more of cohabitation with humans, who probably brought about their demise. Plentiful remains have been found in excellent condition suspended in the frozen tundra. Although the ancient DNA is shattered after millennia in Siberian hibernation, the carefully retrieved fragments are long enough to determine their sequence. Church believes that the woolly mammoth—or a close approximation—can be resurrected, so to speak, by introducing key woolly mammoth genes into the genome of the Asian elephant. The two species are about 0.4 percent different at the DNA level, less than the difference between humans and our closest cousin, the chimpanzee (about a 1 percent difference).
Church made his first trip to meet the Zimovs at Pleistocene Park in August 2018 with a small team including his postdoc Eriona Hysolli. During a grueling fifty-hour journey to the Arctic Circle, the group stopped off in Yakutsk in eastern Siberia. In the lobby of the Polar Star hotel, sporting a CRISPR T-shirt, Church posed for a photograph next to a full-size woolly mammoth replica.9 Conditions for hiking along the banks of the Kolyma River near Chersky, an arctic town 800 miles west of the Bering Strait, were not ideal. “It’s a lovely place if you don’t mind having snow flurries and being eaten alive by mosquitoes in the same day,” Church said.10 That’s on a good day. “The worst day, it’s so cold the mosquitoes cannot live, or there are enough mosquitoes it will literally kill a baby caribou.”11
Donning protective overalls and gloves, Church dissected six beautiful woolly mammoth specimens with a power drill, extracting DNA from fat, marrow, and muscle. Two genes have already been brought back from extinction so to speak, including the mammoth’s hemoglobin gene. While the Zimovs wait for the “elemoths” to arrive, they use a decommissioned tank to remove trees and help other growth. Reindeer, yak, sheep, bison, and horses are already roaming the terrain. Church might need to step on the gas: in 2020, temperatures in a northeastern Siberian town above the arctic circle spiked to a record 100º F.
Beth Shapiro, a paleogeneticist at University of California Santa Cruz, and an HHMI investigator, injects a friendly note of pragmatism. She insists it is not possible to clone a mammoth, which is interesting given that she wrote a book entitled How to Clone a Mammoth.12 Shapiro agrees we could potentially use genome editing to introduce the key base changes, if not all 1.5 million. But then, “we’d have to figure out how to get that individual into a female elephant. Then it would have to be born and raised by elephants. It’s hard to imagine that all of those things would happen and we’d end up with something more than just a slightly hairier elephant.”13
Moreover, Shapiro says, elephants do not fare well in captivity. Until we’ve figured out how to meet the physical, emotional, and psychological needs of edited elephants, we shouldn’t be using them for gene-editing research. She’d rather see the technology used to save endangered elephants, by giving a genetic booster shot if necessary to expand their evolutionary fitness.
Shapiro sees little point in applying heroic measures to bring back extinct species only to place these creatures in a zoo or a park named after a geological epoch. What would we do with resurrected saber-toothed tigers or mastodons? How would millions of passenger pigeons cope with our modern urban environment? But as extinction events in modern times are so often the result of human neglect or suffering, why not apply human technological ingenuity to undo our past mistakes?
A memorial to animal species that have recently gone extinct would include Toughie, the last known Rabbs fringe-limbed tree frog; Sudan, the last male white rhino who was euthanized in 2018 in Kenya; and Lonesome George, the last Pinta Island tortoise from the Galapagos Islands, who died in 2012.14 The woolly mammoth may be the fanciful face of de-extinction, but gene editing offers a ray of hope for a growing conservation movement.
In 1933, zoologist David Fleay filmed Benjamin, the last Tasmanian tiger in captivity in Hobart, Australia. The grainy black-and-white film captured the caged ferocity of this creature, with the trademark stripes across his lower back and the extraordinary elongated jaws. Three years later, the last of the thylacines was dead. Like Lonesome George and Martha, the last passenger pigeon who died at the Cincinnati Zoo in 1914, Benjamin was the last of his kind—an endling.15 It is a word, writes Ed Yong, “of soft beauty, heartbreaking solitude, and chilling finality.”16
Two years before the amphibian in his care at the Atlanta Botanical Gardens died, Mark Mandica, the executive director of the Amphibian Foundation, made a recording of Toughie the frog singing. “He was calling for a mate and there wasn’t a mate for him on the entire planet,” Mandica said. By the time a species reaches that point, it is just one small, inevitable step to extinction. On Oahu, Hawaii, a trailer provides the last refuge for dozens of species of snails, passing what could be their final days in plastic containers destined to become coffins.
Environmentalist Stewart Brand recounts the passing of Martha, the last passenger pigeon, as if she was a blood relative. Her species was the most abundant bird in the world, with flocks reportedly one mile wide and four hundred miles long, variously described as a biological storm, a feathered tempest, and distant thunder. Yet within little more than a decade, by 1914, five billion birds spanning the North American continent were reduced to zero.III Hunters slaughtered them by the tens of thousands. The fate of the birds might have saved the endangered American bison but other species weren’t so lucky. When “Booming Ben,” the last heath hen on Martha’s Vineyard, died in 1932, it was the lead story in the local newspaper. The editorial was an obituary: “There is no survivor, there is no future, there is no life to be recreated in this form again. We are looking upon the uttermost finality which can be written.”17
We are in the middle of an existential extinction crisis—the sixth extinction.18 More than half of all mammalian species have become extinct since 1900. Conservation is a vital tool, as is genetic rescue—increasing the fitness and DNA diversity of species, from California mountain lions to Florida panthers. Genome sequencing is an important tool here for tagging and breeding endangered species—a striking example is a bid to save the endangered Tasmanian devil marsupial, which is threatened by a malignant, orally transmitted cancer. Researchers have released cancer-free devils on a small island off Tasmania in case the main population is unable to stabilize. The endangered black-footed ferret in the Great Plains is at serious risk from bacterial sylvatic (bubonic) plague. Animals bred in captivity can be vaccinated before release, but as proposed by Ryan Phelan and colleagues at the nonprofit Revive & Restore, CRISPR editing offers a means to transfer plague resistance from the domestic ferret to its black-footed cousin.19
Meanwhile, similar strategies are needed to save some other iconic American plants and wildlife. The American chestnut tree population has been ravaged by chestnut blight, a disease spread by a Japanese fungus that was first observed in the Bronx Zoo. William Powell’s team has engineered a hybrid genetically modified tree that contains a wheat gene that neutralizes the acid produced by the fungus. Powell is petitioning the US government to produce a transgenic forest species,20 despite opposition from environmentalists who worry about GM trees. But splicing DNA into its nearest living relative isn’t always possible. The Stellar’s sea cow was hunted to extinction about two hundred years ago. Tempting though it might be to de-extinct this extraordinary creature, Shapiro points out that a baby Stellar’s would be larger than the most logical surrogate. Such an effort at de-extinction would end up a bit messy. She also has bad news for fans of the dodo. De-extinct dodo eggs will be just as appetizing to various animals (including humans) as the originals.