Tasmanian tigers, which were native to the Australian mainland, Tasmania and New Guinea, appeared around 4 million years ago and were the largest living carnivorous marsupial until the time of their extinction.
One of Australia’s most iconic species, the thylacine population declined dramatically on the mainland, likely as a result of hunting by humans and competition with the dingo, leading to its disappearance there at least 2,000 years ago, according to the Australian Museum.
The species persisted on the Australian island of Tasmania—located around 150 miles to the south of the mainland—into the 20th century. But numbers also declined here as well, with persecution by European settlers, who considered it a pest, probably playing a key role, alongside other threats such as introduced dogs.
The last known thylacine died in 1936 but the species was not declared extinct by the International Union for Conservation of Nature until 1982. At the time, international standards dictated that 50 years must pass with no confirmed records of an animal before it could officially be declared extinct.
Over the course of the 20th and 21st centuries, several unconfirmed thylacine sightings have been reported, but none of these have proved to be conclusive.
Colossal, which was founded by tech entrepreneur Ben Lamm and renowned Harvard geneticist George Church, has already been working on the de-extinction of the woolly mammoth. This project is aiming to create a genetically-modified hybrid elephant with woolly mammoth traits that will eventually be introduced to the Arctic tundra.
Now the company is planning to do the same for the thylacine by creating a Tasmanian tiger—or more specifically, something that resembles it—and reintroducing the animal to selected areas in Australia with the hopes that it will have a positive impact on local ecosystems.
The Tasmanian tiger once played a key role in regulating the ecosystem by hunting non-native, mid-ranking predators that preyed on native herbivores. Colossal claims that reintroducing the thylacine proxy will re-balance ecosystems that have suffered biodiversity loss and ecosystem degradation since the apex predator and keystone species disappeared.
“From a Colossal perspective, we are interested in pursuing de-extinction projects where the reintroduction of the restored species can fill an ecological void that was created when the species went extinct and help restore the degraded ecosystem,” Lamm told Newsweek.
To make this dream a reality, Colossal is teaming up with and investing in the Thylacine Integrated Genetic Restoration Research Lab (TIGRR) at the University of Melbourne, Australia, headed by Andrew Pask—a leading marsupial evolutionary biologist and Tasmanian tiger expert—which has already sequenced most of the animal’s genome.
The thylacine was sandy yellowish-brown to grey in color and featured several distinctive dark stripes along its back—the inspiration for the Tasmanian tiger moniker. Its large head was almost dog- or wolf-like, which is why it has also been referred to as the Tasmanian wolf. Despite having certain characteristics that are similar to tigers and wolves, it was unrelated to both.
“The thylacine was a completely unique marsupial,” Pask told Newsweek. “It has a distinctive wolf-like appearance, a striped back, but had a pouch where it raised its joeys like other marsupials. It was also the only marsupial apex predator that lived in modern times.
“Because of this, it played an essential role in the ecosystem in Tasmania and its loss has had profound impacts.”
One example of these impacts is the emergence of the fatal Tasmanian devil facial tumor disease, which shows what can happen in an ecosystem when sick animals are no longer preyed upon and removed from the population, according to Pask.
“Thylacines would have helped control the spread of this deadly disease in Tasmania, and could have helped prevent the now near-extinction of the Tasmanian devil,” Pask wrote in a piece for Pursuit, the University of Melbourne’s multimedia platform.
According to Pask, the fact that the thylacine only went extinct relatively recently increases the chances that de-extinction efforts will be successful.
“The Tasmanian tiger was also aggressively hunted to extinction, with the last animal dying in captivity in 1936,” he told Newsweek. “Its recent loss means the ecosystem in which it once lived is still intact, making this species an excellent candidate for de-extinction.”
In its announcement of the news, Colossal pointed to recent rewilding efforts, such as the reintroduction of wolves to the Yellowstone region in the United States, that are widely considered to have been successful.
Like the woolly mammoth project, creating a thylacine proxy species will involve the use of advanced gene-editing technologies.
“We still can’t create life from dead cells. So in any de-extinction project, the aim is to get as close to the extinct animal as possible through editing the genome of living cells from its closest living relative,” Pask said.
To know what edits need to be made to the genome of the closest living relative—a mouse-like marsupial called the fat-tailed dunnart—the scientists need to be able to compare it to the thylacine’s genome and identify any key differences. Pask’s team has completed the sequencing of around 96 percent of the thylacine genome, although some challenging work remains to nail down the remaining 4 percent.
“One of the key resources for this work is a good genome from your extinct species,” Pask said. “Because the thylacine is a relatively recent extinction, there are many samples in museum collections and the DNA is quite intact, enabling us to build an excellent blueprint of the thylacine.
“We are also working very hard to identify key regions of the thylacine’s genetic code that were essential for its unique development. This developmental and functional work is now being assisted by the outstanding computational biology and gene editing teams at Colossal to build our thylacine genome.”
After comparing the genomes of the dunnart and the thylacine, the team will genetically engineer the former in all the places it is different. This edited genome will then be inserted into marsupial stem cells that can be prompted to turn into a thylacine proxy embryo, which can form a whole animal.
The embryo will be brought to term either through the use of a surrogate mother, or an artificial marsupial womb, which has yet to be developed.
“We’d like the ability to grow the embryo from conception to birth in an artificial womb so we don’t need to use a surrogate mum,” Pask said. “But we can also use a surrogate mum for this. One of the magical marvels of marsupials is that they all give birth to tiny young (about the size of a grain of rice) meaning that even a mouse sized dunnart could give birth to a thylacine joey.”
Significantly, Pask said the technologies being developed for this effort will have “immediate conservation applications” for modern marsupials, which are highly concentrated in Australia—a country with one of the fastest rates of biodiversity loss in the world.
“One of the things TIGRR lab and Colossal are most excited about is the amazing conservation resources that this project will create for currently threatened or endangered marsupial species,” Pask said.
Colossal had previously announced an ambitious goal to develop the first mammoth-hybrid calves in the next six years. While Lamm said the company is not announcing a timeline yet for the first thylacine, he noted that the gestational time for marsupials is measured in weeks compared to 22 months with elephants.
“A large part of our mammoth timeline is based on the nearly two-year gestation of the calves. I think it is safe to assume that the thylacine proxy could be one of the first animals to be brought back,” Lamm said.
According to Pask, Colossal’s ultimate goal for the thylacine would be to return it to Tasmania.
“Like any rewilding, releases would happen in large closures first and the interaction of the species with the ecosystem studied in great detail before an island-wide release would be considered,” he said.
Lamm said the process for any rewilding project needs to be studied “carefully” and the plan should be executed in collaboration with local governments, conservation groups, rewilding experts, ecologists, and Indigenous groups.
“While we are many years away from re-introduction of the mammoth and thylacines back into their native ecosystems, we believe it is important to start partnerships conversations very early in the project,” Lamm said.
“We have started conversations with leading rewilding and conservation groups in Australia and Alaska as well as consultants that work with the local indigenous people groups in both Australia and the broader Arctic circle. Our goal is not buy-in but collaboration throughout the entire project, not only the rewilding aspects.”
Like the efforts to revive the woolly mammoth, Colossal’s thylacine plans have prompted skepticism from some scientists given the significant technical challenges involved.
Kris Helgen, a mammal expert at the Australian Museum, told Scientific American the DNAs of the dunnart and the thylacine are so different—separated by several million years of evolution—that creating an animal that looks like the Tasmanian tiger would be impossible.
Aside from the technical challenges, other experts had concerns over potential ethical issues.
“The whole discourse is about bringing this animal back, but the welfare of the individual animals isn’t really talked about,” Carol Freeman, an animal studies researcher at the University of Tasmania, told Scientific American. “Both dunnarts and almost-thylacines would inevitably suffer in the course of these experiments, which cannot be justified for such an uncertain result. It would be many years, if ever, that cloned thylacines could have anything like the life they may have had—and deserve—in the wild.”
Update 08/16/22, 12:27 p.m. ET: This article was updated to include additional information.
