Bringing an extinct species back to life was once firmly in the realm of science fiction, but as genetic engineering advances rapidly, the prospect of a woolly mammoth again breathing and walking on Earth seems almost within reach. Before fully resurrecting the mammoth, synthetic biologists at the Revive and Restore project are working to resuscitate pieces of ancient genomes with the goal of mixing them with the DNA of living species (Asian elephants—their closest living relatives) in an attempt to create “proxy species”—animals that display the traits of the ancient original.
The end goal, they say, is to populate the tundra region of Siberia known as the “mammoth steppe” with a herd of as-close-to-mammoth-as-possible animals, using them to bring the ecosystem back to its pre-extinction existence. This, naturally, has brought up some ethical dilemmas: Will science take this further and revive the entire woolly mammoth, not just portions of its genome? What is the motivation for doing any of this? And should we be doing it at all?
Woolly mammoths lived in Siberia (among other places) during Earth’s last ice age, also known as the Pleistocene Epoch. They were large mammals, essentially big furry elephants with very long tusks, and their population was quite large, which we know from the abundance of fossils that paleontologists have discovered. There are several theories about how they eventually went extinct about 10,000 years ago. Some scientists believe that humans may have hunted them to extinction, and other theories suggest that the end of the ice age and a warming climate actually caused them to die from heat and dehydration.
Reviving a dead species is a controversial idea. While the scientists undertaking the research see it as a way to restore a ruined ecosystem, detractors see the process as unnatural and even an unnecessary show of scientific hubris. Beth Shapiro, an evolutionary microbiologist at UC Santa Cruz and author of the book How To Clone a Mammoth: The Science of De-Extinction, told Gizmodo that the act of bringing back an extinct creature could be seen as an extension of humanity’s long history of altering other species for our own benefit. She didn’t see such an experiment as unnatural. Shapiro noted that humans have been domesticating and engineering plants and animals for tens of thousands of years; this is what we’re good at and it’s part of our nature, which means it’s a part of the nature of our planet as well.
However, “there is a strong argument to be made that once something is gone for a long time and the ecosystem has adapted to its absence, it’s hard to imagine everything’s going to return to whatever normal you’re describing,” she said. But, she said, the real and lasting benefit of developing these technologies will be to help species that are currently alive—but increasingly threatened by climate change—remain that way. “We have these big brains that have allowed us to make flint technology and 747s and now CRISPR. We can also use our big brains to think about consequences and think long-term. We have the capacity to plan for the future, so let’s do that.”
At a debate at The Kaye Playhouse at Hunter College in New York City in January, some of the world’s leading experts on de-extinction gathered to discuss the pros and cons of fully reviving extinct species. The panel included George Church, a geneticist and molecular engineer who heads the the Harvard Woolly Mammoth Revival project; Stewart Brand, cofounder of the Revive and Restore project; Lynn Rothschild, an evolutionary biologist and astrobiologist at NASA’s Ames Research Center; and Ross MacPhee, curator of the Department of Mammalogy at the American Museum of Natural History.
According to Brand, he and his colleagues see creating proxy species—using portions of extinct genomes in modern animals—and re-introducing them to their previous environments as simply the natural next step in the existing conservation movement. This is “basically bringing biotech to wildlife conservation,” Brand said at the debate. Once the species is developed, it’s a matter of following the same process that has already happened multiple times over in conservation, for animals like wolves in Yellowstone or condors in California. It’s simply “re-introduction of species in places where they haven’t been in a while, transportation of species from where they’ve gotten to now back to where they used to be, and even ecological replacement of one species for another, to serve the same ecological function.”
Brand also noted that the International Union for Conservation of Nature already has in place a series of guidelines specifically for safely creating proxies of extinct species, which, in theory, creates ethical boundaries for the practice.
Church made the case that resurrecting an animal could yield unexpected discoveries—with mammoth revival, specifically, he said scientists might figure out a way to treat the herpesvirus that is ravaging the already-endangered Asian elephant population. The virus strain, which is specific to elephants, has evaded scientists ability to culture in the lab. However, Church and his team, as part of their mammoth project, have sequenced the virus’ genome and are working on synthesizing the virus in hopes of finding a cure. “Is this just something that we’re doing as a stunt, or we’re feeling guilty for our ancestors having killed these things off? I think that’s almost irrelevant,” Church said. “The question is, do these species have something to offer us?”
But NASA’s Rothschild and AMNH’s MacPhee are more cautious. When it comes to full-on de-extinction, they warned of hubris and getting carried away by the desire to perform the science just because we can. The animals, MacPhee argued, have been extinct for so long they have no real connection with the current modern ecosystem. So introducing them back into nature could have a series of unintended consequences—they won’t be able to replicate their ancient microbiome, and they could displace existing species (because ecosystems naturally fill holes when animals go extinct).
“It is said that you can’t walk twice in the same stream. You don’t rejuvenate degraded environments by coming up with implausible jobs for genetically engineered animals whose connection with any real ecosystem either never existed or was severed thousands of years ago,” MacPhee said. “The real de-extinction agenda… is utilising the planet, its resources, asset-stripping it for our purposes. It’s not for repairing ecosystems that, in a sense, don’t need repairing anymore because we’re already 10,000 years down the pike from what they were.”
Rothschild pointed out that in order to revive a long-dead species, there needs to be a recognition that scientists would be working with living beings. And that means risking and impacting the lives of both the revived animals themselves and their modern-day mothers whose wombs would be needed to grow them to full term. (And, MacPhee said, it’s important to consider that these recreated animals would likely be commercialized for human uses, including hunting.)
Rothschild agreed with Church that we need to ask ourselves why we are really focused on bringing long-dead creatures back to life when there are plenty of modern-day animals that are alive and in need of conservation: “Are we making ourselves feel better because our ancestors way back years ago may have been involved in the extinction of this creature? Do we have the right to create individual suffering in order to assuage our guilt?” Humans, agreed MacPhee, are centering ourselves too much in the idea that these animals need to return to the planet. “The real problem, as usual, is us,” he said.
Despite the controversy at the center of de-extinction, the science, for now, is pressing on full steam ahead. The Mammoth Project has already successfully used CRISPR to add a few mammoth genes into Asian elephant DNA to produce what they call “increasingly mammoth-like cells.” Of course, there is a very long road to travel between a few cells and a full herd (or even a single animal). Meanwhile, Revive and Restore is also pursuing other projects, including reviving extinct passenger pigeons, with a goal of hatching the first eggs in 2025. And they’re also working on restoring the extinct heath hen (a species similar to prairie chickens) to Martha’s Vineyard. The goal across all these projects is the same: bring animals back to ecosystems they once played a key role in and learn something along the way. Whether or not the ecosystems will adapt to or benefit from their presence remains to be seen, but it appears that, like it or not, hybrid versions of extinct species will walk the Earth again one day.
Erin Biba is a freelance journalist whose work focuses on how science and technology intersect with climate, the environment, and human health. Her stories regularly appear in BBC, Scientific American, and The Daily Beast, among other publications. Find her @erinbiba.