SEPTEMBER 3, 2017
THE IDEA OF BRINGING previously extinct species back to life through technology has obsessed the public at least since 1990, when Michael Crichton’s Jurassic Park was published. Other books, including Australian novelist John Brosnan’s 1984 Carnosaur, explored the concept earlier, but it was Crichton’s novel — and Steven Spielberg’s 1993 film adaptation — that cemented the idea of what scientists now call “de-extinction” in our popular imagination. Of course, the whole point of Jurassic Park is that attempting such a thing is a colossally stupid idea: a great way to end up with a bunch of dead scientists and theme park guests. While Dr. Ian Malcolm (played by Jeff Goldblum in the film) pontificates about science’s hubris, gleeful Velociraptors go about proving his point far more viscerally. And yet, despite three sequels, each further proving how suicidal the fantasy of de-extinction is, we continue to dream: what if?
It’s not only Hollywood producers that have refused to let go of this scenario. As Helen Pilcher’s Bring Back the King: The New Science of De-Extinction attests, this extremely terrible idea has kept pace with technological progress, and is now closer to reality than ever. Pilcher looks at attempts to resurrect not just the T. rex but also other iconic victims of extinction: the woolly mammoth, the passenger pigeon, the Neanderthal, the thylacine (a carnivorous marsupial that went extinct in Australia in 1936), and Elvis Presley. (The “King” of the title stands for both the King of Rock ’n’ Roll and the king of the dinosaurs.) In successive chapters, she runs down the current state of the art in terms of DNA sequencing and repair, incubation and possible surrogates, and the likelihood of successfully bringing an extinct species back to life. In most cases, while the science is currently out of reach, it won’t be for long. The techniques Crichton drew on for Jurassic Park have become far more refined: incomplete strains of DNA are extracted from extant preserved specimens, filled out, and completed (sometimes borrowing from the closest living relatives). In many cases, this feat is less daunting than what comes next: incubating these new specimens. Woolly mammoth cloning would involve implanting a fertilized egg inside of a living elephant, an undertaking that involves either negotiating a six-foot-long reproductive tract, or going through the rectum and then trying to cut through to the elephant’s womb. Neither process has been successfully accomplished by humans.
Bring Back the King, Pilcher writes in her preface, is meant to celebrate the ingenuity and dogged persistence of the scientists behind these efforts, “their reassuringly thick skins in the face of sceptics and critics who say de-extinction either can’t or shouldn’t be done.” The book’s early pages are unpromising, its boosterish tone and forced jocularity suggesting the worst of pop science. “De-extinction, I hope to persuade you, is not something to be feared or resisted,” she writes in the preface to Bring Back the King. “It’s a force for good, not a tool of the dark side.” There doesn’t seem to be much room in this Manichean worldview for the trickier ethical and philosophical questions raised by de-extinction. Nor does Pilcher seem at first to be much interested in larger questions of biodiversity. “I have unashamedly chosen to feature the species and projects that interest me most,” she writes. “Apologies to the world’s ugly animals and to plants — you don’t get much of a look in.” As such, she focuses primarily on well-known examples of extinction, and what sometimes get referred to as “charismatic megafauna”: well-known and aesthetically pleasing large animals, the kind that have so often driven environmentalism for the past few decades.
But Bring Back the King slowly reveals itself to be a more nuanced account of its subject than this initial impression suggests; indeed, she continually contradicts her own pro-de-extinction thesis, and begins to sound more and more like one of the pesky skeptics her heroic scientists blithely ignore. Through the book, as she considers what it would take to bring back these animals, she concludes that doing so is not worth the effort. The real difficulties, Pilcher reveals, are presented not by the technology itself, but by nearly everything else. An animal, after all, is not simply a living being in isolation: it’s one tiny part of a much larger biome, an intricately working machine in delicate balance. Several of the species she considers are herd animals, which means these animals can’t be brought back in isolation: one cannot bring back a woolly mammoth without bringing back several dozen, enough so that they can flourish and thrive. Add to this the problems with their host mothers: mammoths would have to be bred by in vitro fertilization with their closest living relatives, elephants, but how would such births work with matriarchal pachyderms?
[W]ould a woolly mammoth calf recognise its mum? Would it know to suckle? How about the mother? Would a modern elephant mum caress her hairy newborn with her tactile trunk, or reject it as an aberration? And if she did decide to care for a Pleistocene misfit, how could she possibly teach it to act like a mammoth rather than an elephant?
Once you start thinking through the ramifications of de-extinction, complications quickly mount. Recreating a healthy woolly mammoth, for instance, would also involve developing her gut bacteria, necessary for proper digestion, which means we’d not only have to synthesize the mammoth itself but also successfully identify and recreate a species-specific microbiome. As for the T. rex, Pilcher discusses at length the kind of elaborate zoo enclosure that would be necessary to keep it not only from eating humans, but also to keep it alive. And as we’ve seen from documentaries like Blackfish, keeping massive animals in pens not much larger than themselves leads to depression, aggression, and illness. Is it worth going to such great lengths to bring back the King only to leave him confined and suicidal?
If the task of bringing back several dozen mammoths at once seems difficult, consider the case of the passenger pigeon, which went extinct in 1914. Passenger pigeons flourished not in flocks of several dozen or several hundred, but literally in the billions. The 19th-century ornithologist Alexander Wilson once tried to estimate the number of passenger pigeons in a flock that took over three hours to pass over his house and came up with a rough estimate of 2.2 billion. John James Audubon likewise came up with an estimate in the billions when he tried to count the size of a flock so thick and voluminous with passenger pigeons that the “light of noonday was obscured as by an eclipse.” The passenger pigeon’s extinction, many naturalists now agree, came about in part because the species could only thrive in such enormous groups; once their numbers had been reduced to the millions through hunting and deforestation, the species entered a death spiral and couldn’t recover. Thus, while splicing passenger pigeon DNA with that of related, extant species is not out of the realm of technology, there’d be no way to successfully recreate the species without creating billions of passenger pigeons: anything less would doom them to re-extinction. “We can’t bring back and release a handful of passenger pigeons,” Pilcher concludes. “They wouldn’t stand a chance. With the passenger pigeon it’s all or nothing. We either bring back a flock so large it would darken the sky, or we don’t bother at all.”
Gradually, Bring Back the King becomes a meditation not on de-extinction per se, or the technological advances required to re-engineer a lost animal, but the role that animal once played in a past ecosystem, and how difficult it is to re-fill that niche after the extinct creature has exited the stage. “The de-extinction process isn’t just about ‘making’ the de-extinct animal,” Pilcher writes, “it’s about ensuring there is a place for it and giving it the best start so that one day it will be able to thrive on its own.” There’s no point, for example, in bringing back an animal like the Yangtze river dolphin, whose natural habitat has subsequently been destroyed: it would have no place to go.
“De-extinction isn’t about creating lonely zoo exhibits,” Pilcher insists, “it’s about producing sustainable animal populations that will thrive in the wild.” As such, Bring Back the King is an exercise, almost despite itself, in thinking beyond charismatic megafauna. We can’t bring back the king without considering the queens and knaves, the jesters and the peasants, the court and the castle and the far fallow fields, all of which are just as important as the sovereign. Rather than just naming off famously extinct species, “we should ponder instead what job vacancies there are. What ecological ‘holes’ are there that need plugging? What roles are left unfilled?” Despite her own apparent bias toward the singular and iconic, Pilcher ultimately moves her reader toward an understanding of the importance of biodiversity: the goal is not de-extinction per se, but rather “ecological enrichment, returning communities of animals to the wild where they can live and interact with one another, and positively influence their surroundings.” De-extinction may someday soon be a tool for this project, but it can only ever be a means, not an end in itself.
But why, Ursula K. Heise asks, do we care about animals going extinct in the first place? Why this obsession with creatures dead and gone? Heise’s book Imagining Extinction: The Cultural Meanings of Endangered Species attempts to probe the underlying concerns and contradictions of a question too easily taken for granted. “How, when, and why do we invest culturally, emotionally, and economically in the fate of threatened species?” she asks.
What stories do we tell, and which ones do we not tell, about them? What do the images that we use to represent them reveal, and what do they hide? What kind of awareness, emotion, and action are such stories and images meant to generate? What broader cultural values and social conflicts are they associated with?
If Pilcher’s book reframes the debate of extinction and de-extinction around the importance of biodiversity (instead of technological achievement), Imagining Extinction takes this one step further, asking on a more fundamental level what’s really informing our discussions of extinction and biodiversity in the first place. Again and again, Heise finds that when we talk of endangered and extinct species, or habitats and biodiversity, we are mainly talking about ourselves. Environmentalists’ personal stories often read like religious testimonials: a given species, or even a given animal, awakens a deep sense of empathy and purpose in a writer or activist, who then devotes her or his life to fostering awareness and conservation. These environmentalists’ “engagements with these species,” Heise notes, “gain sociocultural traction to the extent that they become part of the stories that human communities tell about themselves: stories about their origins, their development, their identity, and their future horizons.”
Heise is a literary scholar, and her contribution is to see extinction narratives in terms of genre. One of the most common and long-standing tropes among environmentalists is the recourse to elegy, letting the plight of individual species kindle emotions of loss and grief in humans: “Stories about species that have already gone extinct or may soon disappear frequently rely on the politically mobilizing power of mourning and melancholy.” They also invoke narratives of dramatic tragedy (the inevitable and partly undeserved fall of a powerful figure). This, in Heise’s view, explains our bias toward charismatic megafauna: “the sheer size and the perceived majesty and fierceness of major predators makes it easy to cast them in narratives of tragic falls from grace.” By contrast, Heise goes on to note, animals and plants that don’t fit this trope receive far less attention from conservationists: animals whose appearance is less magisterial, plants and fungi who don’t receive anthropomorphism as easily, and pests whose eradication is actively desired are all often excluded from extinction narratives. “Certain species, in other words, lack the cultural standing that might make them tragic or elegiac figures,” Heise concludes.
Coupled with this is a nostalgia and yearning for a pre-modern era in which humanity lived in perfect harmony with its surroundings, an Edenic landscape in which industrialization and capitalism stand in for the Fall. For many environmentalists, this vision is harshly juxtaposed against a sense that the splendor and beauty of the world has been irrevocably poisoned and lost, an environmental posture that neatly mimics a postlapsarian theology. Books like Bill McKibben’s The End of Nature offer a history of humanity’s interaction with nature that’s structured around a central break, with its attendant sense of mourning for what’s been lost.
This trope has long characterized environmental discourse, particularly in Europe and North America, but anthropologists have begun to push back on this notion, reminding us that pre-modern cultures regularly altered their environments to their own benefit. The Australian outback, for example, was managed by aboriginal cultures through water projects, fire management, and other sophisticated acts of environmental control that lasted thousands of years before white settlers displaced these people. Similar programs have been found in pre-Columbian cultures in both North and South America, including the Brazilian rain forest itself, which has now been shown to have been cultivated by early populations. All of which is to say that this nostalgic yearning for a natural world untouched by human engineering is not only based on a fiction, but carries with it a none-too-subtle chauvinism, with its absurd presumption that non-European cultures were unable to manage (and yes, even harm) the lands they occupied. As Heise suggests,
[T]he idea of nature as Bill McKibben and other North American environmentalists have defined it increasingly appears as, at best, a retrospective misperception and, at worst, a misconstruction of the historical context and ecological impact of Euro-American colonial ventures.
Elegy and nostalgia have since been joined in these last few decades by an increasingly dire apocalypticism, a mood which, in the era of climate change, has begun to infuse environmental discourse to an ever greater extent. Our nostalgic laments for a time now gone are increasingly being drowned out by prophecies shouting the End Times, a secular Second Coming whose imminent destruction will end life as we know it. David Wallace-Wells’s recent New York Magazine piece that outlined an extremely dire picture of global warming is only the latest in a series of doomsday proclamations arguing it’s already too late and we’re all going to die. It’s hard to say whether this kind of fatalism is productive or not; since Wallace-Wells’s piece was published, numerous climate scientists have pushed back both on his data and his tactics. Writing for The Atlantic, Robinson Meyer tried to parse the debate and concluded that a more likely warmed globe might be “a place where sea levels cause mass migration within and without the developed world; where the economy is never great but isn’t in shambles either; where voters fear for their livelihoods and superpowers poke at each others’ weaknesses.”
One thing is for sure, though: the apocalypticism of modern environmentalist discourse continues to distort our perception of nature. Heise describes how Elizabeth Kolbert, in her best-selling book The Sixth Extinction, details the extinction of the golden frog in Panama — an extinction which, scientists ultimately learned, was caused by a previously unknown fungus, one so rare and unusual that a new genus had to be created to taxonomize it. As Heise notes, this fact “elicits no wonder or celebration from [Kolbert], indeed, no comment at all.” Why, Heise asks, is the frog prioritized over the fungus? A perspective less focused on animals innately valued by humans might find it “remarkable that at the moment of investigating extinction, a new species and genus was discovered, so that the reduction and expansion of biodiversity in human knowledge go hand in hand.” But, of course, “the logic of species preferences has it that we care about beautiful or strange frogs (somewhat), whereas fungi leave us indifferent. They do not fit into our narratives except as villains we are glad to rid ourselves of.”
There is no way, Heise argues, to strip away all of these affective filters, to look at the natural world and its animals without human biases and preoccupation. Even relying simply on scientific data reveals another set of innate biases, since “a good deal of the science is shaped by […] the same stories about the decline of nature that have shaped our ecological culture at large.” Take, for example, the International Union for the Conservation of Nature (IUCN), which has long maintained a taxonomy of species’ vulnerability known as the Red List of Threatened Species. Since 1964, the IUCN has been documenting animals on a spectrum from “Least Concern” to “Critically Endangered,” “Extinct in the Wild,” and “Extinct.” The list, which is regularly used to provide data on biodiversity to influence policy making, tilts heavily toward mammals and birds: while the IUCN has evaluated the status of all 5,488 known mammals, and all 9,990 described species of birds, it has evaluated for conservation status only 6,161 of the approximately 1.2 million known invertebrates, only 12,000 out of 300,000 known plant species, and only one type of mushroom out of 30,000 known varieties. So while scientists have long recognized that the public’s focus on charismatic megafauna like wolves and whales distorts the problems with extinction and conservation, their own efforts to quantify the natural world contribute to this problem, ignoring the vast majority of different kind of animal and plant life to focus on evaluating a very narrow band of vertebrates.
If Pilcher’s Bring Back the King asks us to look beyond charismatic megafauna to a more holistic understanding of the world’s ecosystems, Imagining Extinction suggests just how difficult gaining such a perspective may be. The trail of the human serpent, as William James once put it, is over everything. We can look at nature as a resource to be plundered, or we can look at nature as a vulnerable victim of our own excesses, but either way it is we who are doing the looking, and no matter how hard we look, we only ever see ourselves.
Colin Dickey is the author, most recently, of Ghostland: An American History in Haunted Places.
Earth is in the midst of its sixth mass extinction: Somewhere between 30 and 159 species disappear every day, thanks largely to humans, and more than 300 types of mammals, birds, reptiles, and amphibians have vanished since 1500. These rates do not bode well for the future of life on our planet, but what if extinction wasn’t permanent? What if we could resurrect some of the species we’ve lost?
For decades the notion of “de-extinction” hovered on the scientific fringes, but new advances in genetic engineering, especially the CRISPR-Cas9 revolution, have researchers believing that it’s time to start thinking seriously about which animals we might be able to bring back, and which ones would do the most good for the ecosystems they left behind. Indeed, earlier this month, ecologists at the University of California, Santa Barbara (UCSB), published guidelines for how to choose which species to revive if we want to do the most good for our planet's ecosystems.
The two animals at the forefront of this discussion are the woolly mammoth, a hairy, close relative of the elephant that lived in the Arctic, and the passenger pigeon, a small, gray bird with a pinkish red breast once extremely common in North America. The last mammoths died about 4000 years ago, and the passenger pigeon vanished around 1900. Research on reviving both species is well underway, and scientists close to the field think de-extinction for these animals is now a matter of “when,” not “if.”
With that prospect in mind, here’s what we know so far about de-extinction:
Why bring back extinct animals?
As cool as it might be to visit a zoo filled with woolly mammoths, saber-toothed tigers, and giant tortoises, the best reasons for bringing back extinct animals have more to do with ecology than tourism. “If this is always going to be a zoo animal, then stop,” says ecologist Ben Novak, the lead researcher on the passenger pigeon project at Revive & Restore—a foundation devoted to genetically rescuing endangered and extinct species in San Francisco, California. “The goals have to be about ecological restoration and function.”
Every animal in an ecosystem has a function: Bats eat insects, fish clean algae from coral, grazers spread nutrient-rich dung across habitats. Some functions are redundant —shared among multiple different animals—but others are fulfilled by just one or two species.
Both the passenger pigeon and woolly mammoth were functionally unique species, and when they went extinct, their habitats changed dramatically. Harvard University’s George Church, the lead researcher working to de-extinct the mammoth, says that bringing back the giants could help convert the Arctic tundra back to grasslands that existed during the last ice age. He points to research that shows that mammoths and other large herbivores trampling across the ancient Arctic ecosystems helped maintain the grasslands by knocking down trees and spreading grass seeds in the dung. When the large herbivores disappeared, the ecosystem transitioned to today’s mossy tundra and taiga that is beginning to melt and release carbon dioxide into the atmosphere. Reviving the mammoth, Church says, could help slow climate change by shifting the landscape back toward the grasslands. “There’s twice as much carbon at risk in the tundra than in all the forests of the world put together.”
Likewise, the passenger pigeons, whose numbers are estimated to have reached nearly 5 billion at the start of the 19th century, played a dramatic role in shaping the forests they inhabited. Their numbers were so great and their droppings so prevalent and flammable that they destroyed trees and increased forest fires. After their extinction, these healthy natural disturbances ceased, white oaks lost their primary mode of seed dispersal (i.e., via bird droppings), and the forests have never been the same. “The passenger pigeon is a very important ecological species for the habitat that we want to restore,” Novak says.
How do you de-extinct an animal?
There are three main approaches to de-extinction scientists talk about. The first, called backbreeding, involves finding living species that have traits similar to the extinct species. Then scientists would selectively breed these animals to try to make a version that more closely resembles the extinct animal—a process already underway for some extinct species like aurochs. This isn’t really a true de-extinction, but it might still let us fill in missing ecological functions. In the case of mammoths, scientists might try to mate Asian elephants with more body hair than usual, for example.
A second option is cloning. Scientists would take a preserved cell from a recently extinct animal (ideally before the last of its kind died) and extract the nucleus. They would then swap this nucleus into an egg cell from the animal’s closest living relative and implant the egg into a surrogate host. (Researchers actually did this in 2007, and a common goat gave birth to an extinct species, the Pyrenean ibex. The infant lived only 7 minutes however, because of genetic problems with its lungs.) Cloning may eventually give us basically identical genetic copies of extinct species, but we’ll be restricted to animals that went extinct more recently and have well-preserved cells with intact nuclei. The mammoth and the passenger pigeon may never be cloned.
The newest option is genetic engineering. Here, researchers would line up the genome of an extinct animal with that of its closest living relative. They would then use CRISPR and other gene-editing tools to swap relevant genes from the extinct animal into the living species and implant the hybrid genome into a surrogate (or grow it in an artificial womb). This approach doesn’t produce genetically identical copies of extinct animals, but rather modern versions of an animal engineered to look and behave like its extinct relatives. This is the technology being used by the mammoth and passenger pigeon groups.
How close are we?
That depends on what you count as a true de-extinction, which is sort of a gray area. If scientists engineer an Asian elephant to have small ears, extra fur, and more body fat by swapping in mammoth DNA, is it still an Asian elephant?
“If you're willing to accept something that is an elephant that has a few mammoth genes inserted into its genome and therefore is able to make some proteins that mammoths might, we're probably closer to that,” says Beth Shapiro, author of How to Clone a Mammoth: The Science of De-Extinction and an evolutionary biologist at UC Santa Cruz specializing in ancient DNA.
The passenger pigeons project faces similar questions. Novak wants to resurrect the bird using its closest living relative, the band-tailed pigeon, but how many genes need to be swapped to constitute success is somewhat arbitrary. “The two genomes are 97% the same. That 3% has built up over many millions of years and the majority of it is noise,” he says. “So the actual differences are much likely a smaller portion—probably within the realm of several thousand mutations. What we want to find is the key 20 or 100 mutations that affect the traits that are most important.”
There’s also a divide as to what constitutes a de-extinction success for the scientists versus the public. Genetically coaxing to behave like their extinct relatives might restore the ecosystem’s lost function, Novak says. But is that good enough to count? “I don’t think anyone in the world is really going to call it de-extinction unless the bird looks right.”
Even if researchers can pinpoint and transfer those key mutations (a daunting task), DNA is only half the battle. From there it’s a matter of getting the hybrid cell to grow in a surrogate, hoping all the genes work harmoniously together, bringing the hybrid to term, and hoping it acts like the extinct species even though it was raised by a modern relative. If all that goes right, you still need the hybrids to mate and give birth to fertile offspring. “I think the hardest part is getting developmental biology to go,” says Philip Seddon, a conservation biologist at the University of Otago, Dunedin, in New Zealand and the lead author on a recent report by the International Union for Conservation of Nature (IUCN) that issued guidelines for de-extinction research.
It’s a monumental task, but Novak says that if his team can secure enough funding, “there’s no reason that we can’t have the first generations of passenger pigeons by something like 2022 to 2025. Everyone running these projects would very much like to be in 10-year time frames.”
How do we choose which animals to de-extinct?
In their recent publication, Douglas McCauley, an ecologist at UCSB, and his colleagues argue for three criteria to consider when choosing de-extinction candidates: Select target species with unique functions, concentrate on species that went extinct recently, and only work with species that can be restored to levels of abundance that meaningfully restore ecological function.
Although the mammoth and the passenger pigeon might pass McCauley’s first criterion, experts are skeptical about whether they’re truly the best animals to focus on. Shapiro points out that ecosystems are not static and have continued to change since these animals went extinct. “I worry about the dramatic changes to the forest in the eastern part of the North American continent,” she says. “I think there’s a lot we need to understand better about the passenger pigeon’s ecology and the effect that the passenger pigeon would have on that habitat before we can make a sufficiently educated decision.”
McCauley has similar worries: “Forests have fragmented, forests have expanded and contracted. A passenger pigeon that hits that forest again is going to be like a middle-aged guy who really wants to go back to high school and then he gets back there and he’s like, ‘Whoa I don’t fit in anymore.’”
He thinks that de-extinction efforts should instead be focused on recently extinct animals like the Christmas Island pipistrelle bat (Pipistrellusmurrayi), the Réunion giant tortoise (Cylindraspisindica), and the lesser stick-nest rat (Leporillusapicalis). Although not as charismatic as a woolly mammoth, he says these creatures still have habitats to return to and would restore a unique function in their ecosystems. The lesser stick-nest rat, for instance, did what its name implies and built large stick nests in central Australia that became hubs of biodiversity.
What are the risks?
The spread of genes can be difficult to control. We probably won’t lose track of mammoths in Siberia, but what about rats? “It becomes hard to control those sorts of populations,” Seddon says. “And there are the same fears one might have about genetically modified crops—the idea that a modification may move into relatives, may jump in and out, or may not be expressed in the way that you expect.” Scientists are confident that there’s a safe way to proceed, but mistakes may come at a high cost if we can’t put the genie back into the bottle if something goes wrong. “If we lose sight of the true gravity of extinction and overzealously embrace de-extinction as a mitigation tool, it would be really easy to manufacture forests, savannas, and oceans full of Franken-species and Eco-zombies,” McCauley says.
But in spite of any danger, McCauley says his biggest concern isn’t a runaway genetic experiment wreaking havoc on a fragile ecosystem. “Honestly, the thing that scares me most is that the public absorbs the misimpression that extinction is no longer scary,” he says. “That the mindset becomes: Deforest, no biggie, we can reforest. If we drive something extinct, no biggie, we can de-extinct it.”
Introducing (or reintroducing) a new species to a habitat always comes with some risk, but de-extinction scientists point out that we’ve been able to manage that risk successfully with living animals like reintroducing wolves into Yellowstone National Park or beavers into the United Kingdom. There have also been disasters, like the poisonous cane toad in Australia, which was originally imported to help control the gray-backed cane beetles that were damaging sugar crops, but is now spreading across the continent and depleting native populations.
“De-extinction is just the next step in a progression that conservation has already been on,” Novak says. “If you want to restore the ecological function of an extinct species, and you don’t have any living species that will do that, you take the closest living species you can get and adapt it based on the genome of the extinct species.”
IUCN has been dealing with these sorts of issues for years now, and so stands uniquely poised to help regulate de-extinction science’s future. Still, there are no laws requiring that researchers take its advice. The only legal structures governing de-extinction are borrowed from genetically modified organism and cloning research—fields regulated by the U.S. Food and Drug Administration, Department of Agriculture, and Environmental Protection Agency.
Regardless, de-extinction is speeding closer to reality, and now is the time to start thinking about it, McCauley says. “For a long time it was easy to just put it aside because the technology wasn’t there,” he says. “But I don’t think we can do that anymore.”