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Bringing back woolly mammoths and dodos is a bad idea

De-extinction isn’t worth the ethical cost.

A baby woolly mammoth specimen, which looks shriveled and very old, is visible in a glass display case.
A 42,000-year-old woolly mammoth specimen on display at the Field Museum in Chicago.
M. Spencer Green/AP

On January 6, 2000, the bucardo (also known as the Pyrenean ibex, a subspecies of wild mountain goat) was confirmed extinct — for the first time, at least. Conservationists mourned when Celia, as the final bucardo was known, was found crushed beneath a tree in northeast Spain.

But scientists had removed some of Celia’s cells the year before her death, freezing them for preservation. In 2003 came attempts at cloning: Copies of her cell nucleus, containing her DNA, were implanted into 782 eggs taken from domestic goats (a close enough relative to be compatible with the bucardo nucleus). From these eggs, 407 embryos developed, about half of which the team transferred into the wombs of 57 surrogate goat mothers. Of these, seven turned into pregnancies, and one was born successfully.

Profile view of a brown goat with long, ridged horns, against a backdrop of greenery
An Iberian ibex.
Yann Guichaoua/Getty Images

The bucardo became the first species to return from extinction — but only for a moment. The baby’s lung was misshapen, and she suffocated within minutes. For the second time in three years, the bucardo was gone.

Celia’s story illuminates at least three realities facing “de-extinction,” a scientific pursuit aimed at using advanced cloning to resurrect extinct species. First, de-extinction seems technically possible — in fact, it has already been done once, if only briefly. Second, it won’t be easy. And third, there will be blood.

When people talk about de-extinction today, they’re looking at something much more headline-worthy than Spanish goats. Colossal Biosciences, a buzzy de-extinction company founded in 2021 by Harvard geneticist George Church and tech entrepreneur Ben Lamm, has chosen three species to pursue: the woolly mammoth, an elephant species gone for thousands of years; the Tasmanian tiger, or thylacine, an Australian marsupial believed extinct since the 1930s; and the dodo, a large flightless bird from the island of Mauritius that died out in the 17th century.

Black-and-white sketch of a large, eccentric-looking bird with a large curved bill.
A 19th-century rendering of a dodo.
Getty Images

For the first two, Colossal claims de-extinction could bring ecological benefits. With the dodo, a species synonymous with the concept of extinction, it hopes to create “a symbol of hope” for conservation. The company also believes that techniques developed to bring these animals back could then be applied to help protect present-day endangered species.

It’s an exciting idea — after all, who wouldn’t thrill at an Ice Age symbol lumbering through Siberian snow? But while the technical challenges are enormous, the ethical ones are even more so. De-extinction raises fundamental questions about conservation’s priorities, why species matter, and the risks of scientific progress. And as the bucardo shows, one of the most intractable problems is the harm to individual animals: Both the surrogate parents and newborn clones face a risk of suffering and trauma, used as mere instruments in a research project of unclear benefit.

“The first woolly mammoths would be some of the loneliest creatures imaginable”

Church has been planning to bring back the mammoth for more than a decade, working on the problem at his Harvard lab and with the company Revive and Restore before launching Colossal. The project is fueled in part by mammoths’ fame and charisma — the species no doubt generates more funding and interest than, say, bringing back the extinct Christmas Island rat.

But cloning a mammoth will be even harder than the failed effort to clone a bucardo. The goat-cloning scientists had used a still-living cell nucleus from Celia, but no living mammoths remain to harvest cells from, so we have no intact mammoth nucleus, no complete mammoth DNA, and thus no obvious way to transform an elephant egg into a mammoth embryo. Instead, researchers will have to make their own mammoth DNA.

Scientists have already pieced together the species’ genome from fragments of mammoth DNA unearthed from ice, so they have a map for what they are trying to recreate. Colossal’s plan is to use CRISPR gene-editing technology to modify the DNA of an Asian elephant, the mammoth’s closest living relative, inserting specific genes that they consider most essential to being a mammoth: in particular, the hair and other adaptations enabling cold-weather living. The result would not be genetically identical to the mammoths that roamed the planet during the last ice age, but rather a mammoth-ified elephant, a hybrid approximation.

Colossal declares on its website that it’s trying to create a better world “for the planet, for the animals, for the future.” But for many animals, this brave new world could be bleak.

The most direct ethical problems concern the mammoths themselves. The bucardo’s lung deformity was not a fluke. “Rapid aging, ongoing health problems and premature death” are common among cloned animals, philosopher Heather Browning wrote in her 2019 article “Won’t Somebody Please Think of the Mammoths? De-extinction and Animal Welfare.” Many new mammoth babies would likely suffer and die young in the early stages of de-extinction.

The cloning stage also carries risks for the surrogate mothers, who will have no choice about their participation in the project. To gestate a whole herd of mammoths, many elephants would likely have to live in at least partial captivity and deal with the potential trauma of repeated miscarriages. The mother may need a C-section for the birth, as woolly mammoths are larger than Asian elephants — and surgery on an elephant isn’t easy. She would then be confronted by a strange, hairy child whom she may or may not accept.

“Elephants are normally really excited and happy when there’s a new birth,” Matthew Cobb, a biologist and author of As Gods, a book on the ethics of genetic engineering, said in an interview for my podcast, Storytelling Animals. “But they’re going to have this thing that is completely different. … It will smell different. It will behave different.” What if the elephant herd rejects the baby, leaving it alone and orphaned, like a real-life Frankenstein’s monster? “I can’t begin to get over quite how miserable that could be,” Cobb said.

Colossal Biosciences suggests on its website that while the base DNA will come from an Asian elephant, the mammoth embryos will be implanted into African elephants, which are larger and so may handle the birth better. The company also wishes to “eliminate any extra pressure” on the Asian elephant, as it is endangered while the African elephant, the site says, is considered merely “threatened.” That information is outdated, however, as African elephants were upgraded to endangered status in March 2021 (and elsewhere on its site, Colossal does acknowledge that African elephants are endangered).

“The ethical considerations these projects require … are definitely important,“ says Matt James, Colossal’s chief animal officer, in an email to Vox. “We continue to pivot and optimize on a daily basis.” Colossal didn’t respond to questions about the African elephant’s conservation status.

To avoid the complications of animal surrogacy, and to allow for faster breeding, Church has previously declared his intent to develop an artificial womb to gestate the mammoths, a technology that does not yet exist. Even if a synthetic womb were possible, it would only exacerbate the challenge facing the newborn woolies: How will they be raised, with neither a mother nor a father?

Elephants are highly social, culturally complex creatures who live in tight-knit matriarchal bands. Without such a community, “the first few individual wooly mammoths born would be some of the loneliest creatures imaginable,“ philosopher Christopher Preston writes in his book The Synthetic Age.

The first generation of mammoths would likely grow up in captivity, but we have little idea how best to raise them. While paleontological evidence gives some sense of their diet and behavior, the new creatures will be genetically distinct from their wild ancestors, and meeting their exact nutritional and social needs will be guesswork. Normal elephants are hard enough to keep in captivity — the small, enclosed spaces wreak havoc on their bodies and minds, and many zoos have stopped keeping elephants for ethical reasons. Now imagine trying to care for an elephant when we aren’t even sure of basic things like what to feed them.

In response to these and other worries, James explained, Colossal Biosciences has developed a team “tasked with developing not just animal care strategies but socialization plans to rear animals in a healthy setting, even if they are the first of their species to be restored.”

Such planning no doubt can help, but nothing can eliminate the risks and uncertainties of keeping a brand new species in captivity. “Just raising [mammoths] to an age that they are suitable for release [into the wild] may prove to be impossible,” Browning writes, “and the animals are likely to be malnourished and in poor health, with potential psychological and behavioral deficits.”

Mammoths might never be able to survive in the wild

If scientists do succeed at keeping resurrected mammoths alive, they will eventually have to release them. Modern elephants are dependent on intergenerational knowledge transfer to learn the best watering holes and safest migration routes, but how will the first mammoths learn to survive with no generation above them?

Colossal Biosciences hopes that some combination of genetic instinct, surrogate elephant parents, and “on-the-ground animal behavior specialist teams” can teach the mammoths necessary survival skills. But reintroducing captive animals into the wild often fails even under far less exotic circumstances.

Paleontologist Steve Brusatte points out in The Rise and Reign of the Mammals that climate change could also be a hurdle. Mammoths are adapted to Ice Age climates with average temperatures up to 10 degrees Fahrenheit colder than today. If they return, they would be facing temperatures “much warmer than any mammoth ever experienced,” Brusatte writes.

Suppose that mammoths could overcome these obstacles, forging their own path and establishing themselves on the steppe as a happy community. To a hypothetical world of wild mammoths, we’d first have to be willing to put thinking, feeling beings through stress, pain, and often early death. For some animal rights advocates, this alone is enough to oppose de-extinction projects: they believe that nonhuman animals are not mere means to our ends.

For others, the ethical calculus may change if de-extinction brought about sufficient benefit. Perhaps the planet is made richer, in some small way, with one more species in it — one more unique way of the universe knowing itself. The full, joyful lives of some future mammoth herd could arguably justify the sacrifices along the way; we may even owe it to these future mammoths.

The problem with this thinking, write environmental journalist Emma Marris and philosopher Yasha Rohwer, “is that it doesn’t seem like one can have actual moral obligations to what doesn’t exist.” If we create new mammoths, we’ll also be creating immense ethical responsibilities to them. But so long as we don’t, we can focus our moral attention on the living.

The dubious environmental case for de-extincting mammoths

Traditionally, conservation biology has not evinced much concern for the well-being of individual animals, instead prioritizing biodiversity — the health of whole species and ecosystems. Under this framework, a new mammoth population could be justified if it creates concrete benefits for the broader ecosystem.

Mammoths indeed once played a key role as ecosystem engineers: They snapped trees, trampled grasses and mosses, created depressions that became ponds, and otherwise transformed the steppe grasslands in ways that could theoretically help today’s endangered inhabitants such as the reindeer and Saiga antelope.

But a resurrected mammoth would not fix what has primarily been killing these creatures, namely hunting, disease, and the loss of habitat through the expansion of grazing and industry. De-extinction or not, addressing threats like these should be the most urgent conservation priority. In fact, introducing mammoths might invite even heavier human presence to the region: Church himself speculated in a 2019 interview with Harvard Magazine that mammoths could support “business models” including “tourism, meat, hair (following a sheep model of seasonal removal), and maybe legal ivory.” Church didn’t respond to a request for comment about these statements.

Another potential mammoth benefit is fighting climate change: Some scientists believe that mammoths’ compaction of soil could slow the thawing of Arctic permafrost, which releases the greenhouse gas methane. But it could take decades or more to breed enough mammoths to impact a sizable chunk of the permafrost, considering their slow reproductive process.

Even if the benefit were significant, Browning said in an email, it seems unlikely that bringing back a long-extinct creature is the best way to reduce methane emissions. If humans are creative enough to bring back the mammoth, surely we’re creative enough to find other ways of dealing with the permafrost.

Beyond the mammoth

De-extincting other animals is no less fraught. Different species present overlapping but distinct scientific and moral challenges, and de-extinction candidates may best be judged on a case-by-case basis.

“Mammoths seem to me to be the worst candidates due to their size and the likely complexity of their behavioral and social needs,” Browning said in an email, but species that went extinct more recently, she believes, may be easier to resurrect, because we may know more about their dietary and habitat requirements, and to at least some extent their original ecosystems still exist.

Pale color sketch of an animal that looks a bit like a wolf, but orange and with tiger-like strikes. The animal is crouching down and appears to be in a hunting pose.
Illustration of a thylacine, or Tasmanian tiger.
Getty Images

But in most cases, those ecosystems would hardly be safe. Most of the serious de-extinction candidates were wiped out due to human impact such as overhunting or habitat destruction. These pressures would likely still exist should they be resurrected. Philosopher Thom van Dooren and anthropologist Deborah Bird Rose wrote of de-extincting the thylacine, or Tasmanian tiger: “What sense does it make to dream of returning the thylacine when we cannot even ask people to make room for dingoes? How have the sheep farmers that once played a pivotal role in the extinction of the thylacine in Tasmania so changed their ways that this resurrection will be a success?” Without a protected area to return to, de-extinct animals might be relegated to zoo curiosities or exotic pets.

Color sketch of a serene-looking, blueish gray pigeon with a coral-colored breast and eyes
Rendering of a passenger pigeon.
Getty Images

Ethicist T.J. Kasperbauer raises similar worries about the passenger pigeon, which the company Revive and Restore is attempting to revive. The North American bird once flew in flocks of hundreds of thousands, but might again be hunted and treated as a pest if it reaches its former numbers. Kasperbauer also cites some scientists’ fears that passenger pigeon flocks are not self-sustaining beneath a certain size — that is, we would need to breed a truly ginormous number of birds to be able to successfully release them into the wild.

Alex Lee, a philosopher at Alaska Pacific University, is most concerned about the moral hazard: If de-extinction technology becomes developed and widely accessible, will people become less worried about extinction in general? After all, why go through too much trouble to save a dying species when we could just bring them back a few years later? Empirical research is still needed to figure out how people’s attitudes are changed by the prospect of de-extinction, Rohwer and Marris suggest. Perhaps a newborn mammoth could inspire a sense of awe and wonder at the natural world that drives people to fight harder for all life, rather than seeing it as expendable.

For Beth Shapiro, a scientist involved in both Colossal and Revive and Restore, de-extinction itself is not really the point. Instead, she explains in her book, How to Clone a Mammoth, the scientific tools developed to resurrect dodos or mammoths could be used to help other creatures. Colossal’s James told Vox that the company is partnered with several elephant conservation organizations, and that its “advancements in assisted reproductive technologies,” “genetic engineering for disease resistance,” and more will benefit both de-extinction and existing wild elephant populations.

For instance, the company explains on its site, Colossal researchers are investigating how to insert genes into Asian elephants that would instill resistance to deadly elephant herpesviruses. De-extinction technology could also bring back species we lose in the future. While this at least seems ethically preferable to mammoth de-extinction, any potentially invasive research program involving sentient beings should inspire caution.

James said that much of the company’s testing is being done using AI or in vitro cell cultures, rather than in live animals. If and when live animals do become involved, he says, “whether that be a lab mouse or an elephant,” the company has bioethicist advisers, an independent Institutional Animal Care and Use Committee (IACUC), and an internal review process “to decide if and how we should pursue every aspect of our work. … Animal welfare, well-being, and health are at the forefront of our minds.”

These considerations are encouraging — but they can’t indicate that a research project is ethical because the Animal Welfare Act, which governs animal testing in the US, is highly limited and says little about what can be done to animals in experiments themselves, as Vox has reported. Most animal research facilities have an IACUC, but they do little to prevent research that many find unjustifiable.

De-extinction should be decided democratically

The ethical issues raised by cloning, captive breeding, wildlife reintroductions, and animal experimentation writ large are not unique to de-extinction, and de-extinction is far from the worst threat to animal well-being today. But they still matter, and they can force us to consider our relationship with animals more broadly. When we imagine a lonely newborn mammoth, we might be moved to consider an individual animal’s welfare and subjective well-being in other decisions around wildlife.

Just as important: Who is the “we” who makes these decisions? Decisions about the dodo, for instance, should be made in concert with the people of Mauritius, where the bird’s ancestors lived for potentially millions of years, not solely by scientists thousands of miles away. Colossal “understand[s]...the importance [of] building mechanisms to give a voice to the local communities that co-exist with these animals,” James said. But mammoth expert Tori Herridge thinks more must be done to democratize the process. After declining a position on the company’s advisory board, she wrote in Nature, “The ethical road to de-extinction has to include informed citizen voices. … Let the people decide the future world they want to build.”

How to do this, exactly, will be difficult. But modern genetic technologies are too powerful to be controlled even by well-intentioned scientists, let alone for-profit corporations — some deliberative democratic process is needed. And more complicated still, that democracy must strive to represent non-human voices. Any decision on resurrecting species must consider the needs and desires of the elephants, pigeons, and other creatures whose lives would be upended, constrained, created, and destroyed to make de-extinction a reality.

One day, new knowledge or technology may allow us to avoid de-extinction’s ethical costs. But until then, the woolly mammoth should remain nothing more or less than a memory.

Dayton Martindale is a freelance writer and editor covering climate, ecology, animals, and politics. He hosts Storytelling Animals, an environmental books podcast, and serves as editor-at-large for the rural news publication Barn Raiser. This year, he will begin a PhD program in environmental studies at the University of Colorado Boulder, studying the ethics, politics, and policy of human-nonhuman interaction.