Is de-extinction only a pipette dream? This startup has a big, expensive plan to find out.

Colossal is promising to turn long-dead mammoths, dodos, and thylacines into living hybrids that can be returned to nature. Critics want to see the results.

ON A COMPUTER MONITOR, in a laboratory half the size of a galley kitchen, I’m taking a look at the future. But the grainy object on the screen isn’t all that remarkable. It’s just a horse egg in a petri dish, blown up to the point where I can see the outline of its outer membrane. That’s when a white-coated scientist directs my attention to the device at my right: a high-powered microscope projecting the image of the horse egg, with two metal spikes the size of syringes angled at each side of the plate. Beneath me on the floor is an orange pedal I’m instructed to press with my foot. Suddenly, on the screen, I see a laser beam carve an incision into the membrane of the horse egg, like a hot knife going through butter.

In a few more years, the same laser-guided system will be used to punch a hole into an egg taken from an Asian elephant, remove the nucleus of that cell, and insert a nucleus containing edited genes required for surviving arctic temperatures, such as fuzzy hair and extra fat—all in the pursuit of creating the closest animal to a woolly mammoth to walk the Earth in many millennia.

The lab is one stop on my tour of the bioengineering facility of Colossal Biosciences. Co-founded in 2021 by Harvard geneticist George Church and serial entrepreneur Ben Lamm, Colossal is the world’s first de-extinction company. Its purpose? To rewild lost species. In June, I traveled to Dallas to get an in-person look at the 26,000-square-foot research facility where the startup’s innovative might is brought to bear. 

Colossal’s plan is to design a hybrid of a prehistoric woolly mammoth—which Church has described as “the cuddly version of a velociraptor”—as well as the thylacine, a marsupial from Australia and Papua New Guinea that died out in 1936, and the quintessential symbol of human-made extinction, the dodo, the last of which was snuffed out on its native island of Mauritius in 1662. 

Scientist in white coat looks into eyepiece as nearby video screen shows closeup of embryo in Colossal's lab
Colossal senior scientist Anna Keyte checks the progress of growing avian embryos in the company’s lab in Austin, Texas. John Davidson

De-extinction as an idea is not new. Church has discussed engineering a new lineage of woolly mammoths from frozen genetic material since 2008. The nonprofit organization Revive & Restore harbors aspirations of returning the extinct passenger pigeon to the skies. Scientists at the San Diego Zoo Wildlife Alliance hope to make gametes from cryopreserved skin cells of northern white rhinoceroses, a subspecies down to its last two members. What makes Colossal unique is its unicorn status: It has raised $225 million in investment capital in just two years and is now valued at $1.45 billion. Peter Thiel, Chris and Liam Hemsworth, the Winklevoss twins, Paris Hilton, and even the not-for-profit partner of the Central Intelligence Agency have all chipped in. (So has Matt Sechrest, co-founder of Recurrent Ventures, which owns Popular Science.)

Which raises a thorny question: What happens when you venture-fund nature?

Lamm, an energetic 41-year-old with a shoulder-length mop of dark hair, is well versed in this space. He comes from the tech world and has founded six different companies in his native Texas. (One of them, an artificial intelligence defense platform that counts the US Space Force and NASA as customers, was just acquired by a Texas-based private equity firm in August.) But the focus on money and investors belies the larger point. De-extinction, Lamm says, is a way to return keystone species to degraded ecosystems while developing the techniques to support future conservation projects. If we can genetically engineer a dodo, for example, what’s to stop us from breeding a more disease-resistant offshoot of Hawaiian honeycreepers, who are currently being decimated by avian malaria?

“[Some of] the technology advances that are going to be necessitated to de-extinct a creature are exactly the same technologies that will be necessary to help creatures not fall over the brink,” says Kenneth Lacovara, a paleontologist and geologist at Rowan University who agrees with Colossal’s mission.

computer-generated x-ray-type model of internal bones and organs of extinct thylacine
A computer model of the internal organs and skeletal structure of a young thylacine specimen could help with engineering future marsupial hybrids. Colossal Biosciences

Critics, meanwhile, say it’s misguided to scrape the natural world for genetic material to fulfill scientific whims. Why de-extinct obsolete species when there are more than 1,300 endangered and threatened ones in the United States alone that need protection? Observers also argue that introducing the genetic traits of dead creatures into modern analogs is not a means to conservation when the habitats of still-living endangered animals are continually under threat.

“We should protect species and do what we can,” says Lamm. “But that current model of just putting our arms around it, protecting it, just doesn’t work at the same speed at which we are destroying environments.”

The pioneering work Lamm speaks of will take decades. The company expects to birth a mammoth-like calf in about five years and then build up to a whole herd of woolly proxies. But in Colossal’s vision, the reintroduction of lost species is not only a way to right the wrongs of humanity but also a way to generate significant scientific know-how—so we can sustain species currently at risk in an increasingly inhospitable world, lest they perish forever.

THAT AN EARTHBOUND CREATURE like a woolly mammoth could vanish was once utterly unbelievable. French naturalist Georges Cuvier eventually delivered the sobering truth. He made his bones in 1790s Paris studying elephant fossils. Concluding that the remains were too distinct to be directly related to modern-day elephants, Cuvier posited the notion of espèces perdues, “lost species.” It was clear to him that the skeletons belonged to another megafauna that had vanished. Voilà: Extinction became a dilemma for modern science to solve.

Lamm’s fascination began with an introductory call to Church in 2019. His business acumen lay in using artificial intelligence for satellite software systems, and he wondered if the machines could also help with synthetic biology—the practice of building living systems from DNA and other small molecules. At the end of the call, after he idly asked Church what else he was working on, the mammoth comeback came up. “I was like, ‘Wait, what?’ I stayed up all night reading” everything Church had written about his quest, recalls Lamm. Soon he teamed up with the geneticist to form Colossal, where he is now CEO. In September 2021, the company launched with $15 million in seed funding and announced its plan to revive a version of the woolly mammoth.

Colossal widened its focus to the thylacine after Lamm was introduced to Andrew Pask at the University of Melbourne, who had already been conducting research on the marsupial and now consults on the company’s project on the species. More money came in, at which point investors asked the obvious question: What can we do for extinction’s mascot, the dodo? Beth Shapiro, who co-directs the Paleogenomics Lab at the University of California at Santa Cruz and has studied the flightless bird’s genome for almost two decades, advises Colossal’s avian genomics work. A few years ago, she and collaborators from other institutions had assembled the first complete genome of the dodo.

To any expert in this field, the tools in Colossal’s Texas labs aren’t unfamiliar. There are desktop gene sequencers and centrifuges. Hooded substations in a tissue culture lab for manipulating bits of animals. Computers that peer into sequenced DNA and analyze nucleotide bases. The laser-guided microscope I saw in the embryology lab is a proprietary device Colossal invented. In a company of 116 people, more than 60 are cell engineers and geneticists using these tools daily.

What’s important to understand, however, is that despite its talk of de-extinction, not to mention the graphics peppering its website, Colossal will never resurrect an animal. There’s no way to truly reanimate an extinct species by synthesizing its DNA from scratch—even with cutting-edge technology and living cells from an organism, and there are no such cells of a mammoth, dodo, or thylacine. 

“It’s still not possible to bring an extinct species back to life if what you mean is an exact copy,” says Shapiro. “What we’re working to do is to create proxies for these extinct species using some of their traits.”

scientist extracts DNA sample from woolly mammoth specimen
Eriona Hysolli, head of biological sciences at Colossal, samples DNA from a frozen woolly mammoth in Siberia. Colossal Biosciences

Colossal’s real aim is to take existing species closely related to extinct animals, modify their DNA to give them traits similar to the company’s de-extinction targets, and place them in ecological settings that are as similar as possible to where previously extinct species once lived. For the dodo, it may be the Nicobar pigeon, a living cousin that inhabits islands in southeast Asia. For the thylacine, it’s the fat-tailed dunnart, a marsupial that resembles a rat. Modern-day elephants are also in the mix: Although the woolly mammoth has been gone for anywhere from 4,000 to 10,000 years, it has a close relative in the Asian elephant—so close, in fact, that more than 99 percent of the animals’ genomes are identical.

“A mammoth to an Asian elephant is more closely related than an African elephant is to an Asian elephant,” says Eriona Hysolli, Colossal’s head of biological sciences, who works closely with Church out of his lab in Boston and supervises the mammoth work.

What Colossal scientists are trying to do is understand links between genotype and phenotype: how the sequence of letters in DNA code translates to how an animal looks and behaves. Hysolli says they are targeting about 65 sequences in the mammoth genome that confer various cold-adaptive traits, like subcutaneous fat, woolly hair, and dome-shaped craniums. In the genome engineering lab, computers compare the ancient DNA of the mammoth to that of the Asian elephant to identify areas of the elephant genome that must be modified in a future hybrid to express extinct characteristics. 

“Are all the phenotypes there? Are all the ecological functions there? That is, for us, what we’re saying is de-extinction,” says Matt James, a former director of animal care at the Dallas Zoo, now chief animal officer at Colossal. “We de-extincted critical genes for these species.”

To do that, Colossal is trying out pluripotent stem cells, which are capable of turning into any adult cell type. Those are created inside the company’s tissue culture lab from Asian elephant cells donated from various sources. (Colossal partners with 11 zoos across the US.) This is where genome engineering and cell manipulation will eventually intersect. There are two ways to insert mammoth genes into an elephant cell: use the ever-popular CRISPR/Cas9 gene-editing tool to insert enzymes that make changes to nucleotide bases along the Asian elephant’s genome, or make multiple sequence changes at once, a process known as multiplexing, with the help of other molecular tools. 

close-up of stem cell genes from fat-tailed dunnart appear in bright colors
Researchers can customize a long-tailed dunnart’s embryonic stem cell by altering the SOX2 genes (seen here in fluorescent colors). Colossal Biosciences

Finally, to complete the mammothification of an Asian elephant, a nucleus from a regular elephant egg would be swapped with the nucleus from a cell modified with snippets of the mammoth genome—something they are planning for by early 2026 so Colossal can meet its projected date of 2028. Known as somatic cell nuclear transfer, it’s the same technique scientists used to make the famous clone Dolly the sheep in 1996. Colossal’s scientists are already practicing with gametes from animals like cows and horses. 

Once the hybrid egg develops into an embryo, it will be implanted into a female Asian elephant. The gestation period for a mammoth is the same as for an Asian elephant: around 22 months. And if that fetus survives long enough to be born, it should, hypothetically, be adapted to cold weather because it possesses mammoth traits. It probably won’t have massive tusks, but it will be 200 pounds of flesh, fat, and protective fur.  

James is confident that Colossal will be able to produce a mammoth by implanting a modified embryo into a surrogate. To increase its chances, though, he says the team will develop multiple eggs and work with a couple of female elephants. Even so, the first generation of mammoth hybrids won’t go anywhere near the wild. “They will be in what we would call a managed care facility,” says James, which means a sanctuary or some other facility where their anatomy, physiology, and behavior can be studied regularly. The mammoths will have to prove they have the skills to live and thrive independently in the wild. 

Skeptics might say the means, in this case, don’t justify the end. “It’s not necessarily accurate to say that the animals will benefit more by being brought back to life rather than just staying dead,” says Zohar Lederman, a physician and bioethicist at the University of Hong Kong. 

Others are much more strident. “It seems like a terrible idea to me,” says Karl Flessa, a geosciences professor at the University of Arizona who centers his research work on conservation biology and habitat and species restoration. “Why are you bringing back a Pleistocene animal as the world continues to warm and all of the habitats that were once available for mammoths are pretty much gone? Why would you want to do that?”

IN AN OP-ED for Rolling Stone in July, Colossal CEO Lamm argued that the company’s efforts are absolutely essential to sustaining the biodiversity of the planet. “I came to the conclusion,” he wrote, “that the question is no longer should we practice de-extinction science but how long do we have to get it right.”

Global authorities continually point out that Earth is currently in the middle of an extinction crisis. In 2019, the United Nations published a landmark report stating that one million animal and plant species are close to dying out, which is more than ever before in our history. A subsequent report issued in 2020 by the World Wildlife Fund found that wildlife populations had decreased by two-thirds in the last half-century alone, mainly due to human activities like deforestation, insecticide use, and poaching. In May, four researchers published a study in the journal Nature Ecology & Evolution linking climate change to another mass extinction. They evaluated almost 36,000 species on land and in the ocean and used climate models to show that 15 percent of those organisms will experience dangerous and potentially fatal temperatures if the planet warms by 1.5 degrees Celsius by 2100.

Asian elephant walks through grass; illustration of woolly mammoth stepping across stream
The Asian elephant (left) has the most genetic overlap with the woolly mammoth (right) of any living species. From left: AB Apana / Getty Images; Colossal Biosciences

Lamm, Church, and the rest of Colossal’s corporate chain contend that those sorts of numbers animate the underlying principle of the company: that their lab-made proxies aren’t just some well-funded science project—they can legitimately be used to build resilience in species by pushing them toward the right adaptations in a changing world. The mammoth-elephant hybrid is the classic example. Asian elephants are listed as endangered by the International Union for Conservation of Nature. Merging snippets of woolly mammoth genome with the Asian elephant might give the big mammal a chance to inhabit a place like Pleistocene Park, a large tract of tundra in Russian Siberia that’s free from our interference.

“People say we should be working on endangered species. That’s exactly what we’re working on,” Church told me via video call the day after I toured Colossal’s lab. “One of the advantages of making a hybrid starting from an endangered species is that you give that endangered species a whole new place to live, which is much larger and less encumbered by human conflict than their current location.”

At the same time, the genomic sequencing Colossal currently leads is being put toward the development of a vaccine for a herpesvirus—the primary cause of death of young Asian elephants in zoos in North America.

But geneticist Stephan Schuster remains incredulous. Schuster was part of the Pennsylvania State University team that, in 2008, was the first to sequence nearly a full genome of an extinct animal when it assembled 2.9 billion base pairs from the genome of an 18,000-year-old woolly mammoth found in Siberia. “If there is a single person on the planet that I would trust to get the project accomplished, it is George Church,” he says. But, he adds, talk of resurrecting a mammoth has gone on for a decade, without much to show for it.

Schuster has a long list of queries about Colossal’s methodology. Will changes made to Asian elephant DNA lead to unpredictable mutations elsewhere on the genome? How many elephant pregnancies must happen to create one transgenic animal? How do you implant a mammoth-hybrid embryo into the uterus of an Asian elephant, which is deep inside the animal? “Just show success,” says Schuster. “All the rest, it’s just blah, blah, blah, blah.”

Another one of the scientific community’s main criticisms of Colossal is money versus impact. A $225 million capital fund for species restoration is nothing to sneeze at. Meanwhile, based on an analysis by the Center for Biological Diversity and other conservation groups, the US Fish and Wildlife Service requires a total of $841 million to fully fund all recovery efforts under the Endangered Species Act. The agency’s 2023 budget for protection efforts is just $331 million.

Nicobar pigeon sits on rock; dodo illustration
The Nicobar pigeon (left) has a modern island lifestyle that could meld well with unique attributes of the dodo (right). From left: Tambako the Jaguar / Getty Images; Colossal Biosciences

Colossal retains the exclusive license to commercialize any biotechnology that emerges from its de-extinction projects. Lamm assures me that anything that might be applicable to human healthcare—for gene therapy and the like—will be strictly proprietary. The one exception is how the instruments, like its laser-guided embryo-editing tool, are employed for various species preservation projects. “We may open-source some of the technology for its application to conservation,” he says.

The proxies themselves, once born, are also likely to be wholly owned by Colossal, at least for a while. Early hybrids will live in a vast fenced-in area like a nature preserve. Once there are enough members of each de-extincted target that can live and survive in the wild, they will start being released. And that’s when, Colossal says, ownership transfers to the natural world.

“They would become more of a natural resource for the area where they’ve been rewilded,” says chief animal officer James. It would be similar to how we might view elephants already existing in the wild. A specific country doesn’t own an African elephant—although it might be argued that those countries do have a responsibility to protect wildlife. (One location that Colossal is considering for future mammoths is North Dakota; the state development fund invested $3 million in the company earlier this year.)

Skeptics of Colossal’s overall strategy also wonder what will happen should de-extinction efforts prove successful. Creatures that have been gone for tens, hundreds, and thousands of years would suddenly emerge into a vastly different world—one that, by the very metrics Colossal cites, is already far too dangerous for the organisms that are still alive.

“Having mammoths isn’t going to solve any of those problems,” says Ronald Sandler, director of the Ethics Institute at Northeastern University. “It’s not going to reduce habitat loss. It’s not going to reduce carbon emissions. It’s not going to help us prevent a currently extant species from going extinct.”

Take the infamous flightless dodo, which could be an inspiration for shoring up vanishing populations of endemic island pigeons. The scientific process for creating its replacement is different from those for the mammoth and thylacine proxies. Currently, there’s no way to genetically edit a living bird. Scientists can manipulate the egg cell of a mammal when it’s ready to be fertilized because its nucleus is easy to get to—but the yolk of a bird egg makes that impossible. Instead, Colossal plans to create primordial germ cells, which can become sperm or egg cells, and inject them into developing embryos of a living bird. One prime candidate is the Nicobar pigeon. A male and female Nicobar would each then grow up with gametes containing the edits required to birth offspring with the characteristics that so distinguished the dodo, like its flightlessness, S-shaped body, and hooked beak. Say that works multiple times over, enough to generate a population of dodo proxies. What good does that do if its historic home of Mauritius is filled with invasive predators and may be flooded in 100 years?

Fat-tailed dunnart sits on wooden stick in grassy area; rendering of thylacine in swampy, rocky area
The fat-tailed dunnart (left) is being studied for “assisted reproductive technologies” to aid the thylacine (right) de-extinction project. From left: Auscape International Pty Ltd / Alamy; Colossal Biosciences

“I’m critical of de-extinction, but I also do think it has a role to play,” says Tom Gilbert, a paleogenomics researcher at the University of Copenhagen. He also worked with Shapiro to produce the dodo genome and is a member of Colossal’s scientific advisory board. In his eyes, releasing “a bad mutant mismatch of something else not adapted to the environment” doesn’t strike him as an effective means of ecosystem restoration. “But if you can excite a generation of young people using crazy de-extinction projects to love nature and get into science, that is going to save the world,” he adds. “If it requires a mutant mammoth-elephant hybrid to get the people excited, that is a valid reason to do it.”

THE BIGGEST OPEN QUESTION is whether Colossal can and will use the bioengineering toolkit it’s developing for the greater conservation good. The startup certainly claims it will: It recently joined forces with Thomas Hildebrandt, another member of its scientific advisory board, who currently leads BioResponse, an international consortium attempting to create a new population of northern white rhinoceroses. Colossal’s supporting role will be to gather DNA from museum specimens of the near-extinct species, analyze the data, and then use its gene-editing tools to help create more diverse northern white rhino embryos. The genetic variation should, in theory, help protect the rare mammals from disease in captive-breeding programs and, eventually, in the wild.

Still, there is no hybrid mammoth, thylacine, or dodo to point to at the moment. For Lamm, generating those ancient species is the priority. “If Colossal does nothing else in conservation or de-extinction, and we cure elephant endotheliotropic herpesvirus and are responsible for saving elephants, that was a pretty good day,” he tells me just after our walk-through of the lab. “But fundamentally…if we aren’t successful in our de-extinction efforts, I will personally not see it as success.” 

Yet there is a danger in pursuing ghosts and still-fictional creatures. Mammothlike elephants or big-beaked pigeons or fiercer dunnarts could overshadow wildlife teetering on the precipice of oblivion right now. After all, who cares, really, about the orangefoot pimpleback, an endangered freshwater mussel, or the Oahu tree snail?

When I present paleontologist Kenneth Lacovara with that conundrum, he deems it a false choice. “Yes, we have to do everything we can to conserve species that are on the brink,” he says. “And yes, we should try to bring back species that have gone extinct that were pushed into extinction by humans. I think that’s justice. Those two things are not at odds with each other.”

Maybe not. Could the return of a mammoth-like beast backed by millions of dollars in capital funds stabilize an ancient Arctic ecosystem that traditionally helped trap greenhouse gases deep inside the frozen tundra? “When a species is introduced to a landscape, you can’t always predict what every one of the consequences is going to be,” says Shapiro.

“If we aren’t successful in our de-extinction efforts, I will personally not see it as success.”

Ben Lamm, CEO of Colossal Biosciences

But we certainly know what happens when a species is removed from where it belongs, be that the fault of overzealous humans or larger environmental degradation. Consider the reintroduction of gray wolf packs to Yellowstone National Park, perhaps the preeminent example of the positive ecological effects born from restoring fauna in their native habitats. As one of the top predators in the region, wolves helped bring other wildlife and natural cycles back into balance. 

We don’t know what will happen if a woolly mammoth hybrid makes its debut in the 21st century. But the future that Colossal envisions is one in which the act of protecting the animal kingdom goes beyond building fences, zoos, or preserves—one in which humans invest in and invent tools that could prime species for survival, including those that haven’t been dead for thousands of years. 

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Andrew Zaleski


Andrew Zaleski is a freelance journalist of nearly a decade who writes frequently about science, technology, and business for a variety of magazines. He’s a contributing writer at Popular Science, and began writing for the magazine in 2014. He lives near Washington, D.C., with his delightful wife, as well as his dog, Finnegan, who is also delightful.