A plan to bring the Tasmanian tiger back from extinction raises questions

If you haven't heard of the Tasmanian tiger, it's not because it's unworthy of discussion: it's famously not a feline but a dog-like marsupial, a predator that humans hunted to extinction. The last known specimen died in a zoo in 1936.

Now the "de-extinction" company Colossal Biosciences wants to genetically resurrect the Tasmanian tiger, also known as the thylacine (Thylacinus cynocephalus) or the Tasmanian wolf.

"Whatever you call it, this mythically beautiful carnivorous marsupial was a true masterpiece of biological advancement," the company says of the project. "Yet, the story of its extinction is a tragedy of human interference and aggression."

The thylacine had trademark stripes and, rare in the animal world, abdominal pouches in both females and males. Australian researchers have called it "a dingo with a pouch" or "a dog with a pouch" — but its DNA also has a lot in common with the kangaroo.

Colossal, which has previously aired plans to resurrect the woolly mammoth, is intent on giving the thylacine "a second chance at life."

Here's a rundown of some of the big questions the project raises:

Is the thylacine capable of living again?

Humans have been blamed for the animal's extinction, especially after a bounty program was instituted in Tasmania to protect sheep and other animals. But in 2017, Andrew Pask, a biosciences professor, led research that found the thylacine also suffered from a lack of genetic diversity.

"The population today would be very susceptible to diseases, and would not be very healthy" if it still existed, Pask said back in 2017.

Pask is now part of Colossal's new project to bring the thylacine back. When asked if his view on its viability had changed, he said via email that the plan will incorporate diverse DNA sources.

"We have now sequenced many thylacine specimens and hope to continue doing so in this new partnership with Colossal," Pask said in an email to NPR. "Even species with low genetic diversity can be brought back to healthy population numbers again if they are managed correctly."

The goal, he said, is to bring back "a good number" of animals to help ensure healthy diversity in the new population. And while the thylacine was seen as struggling in the wild, any new population would be closely monitored, he noted.

How would the animals be created?

For one thing, it's not cloning.

"Cloning is a very specific scientific process. That process requires a living cell," evolutionary biologist Beth Shapiro of University of California, Santa Cruz told NPR when talk of resurrecting the mammoth gained new currency in 2015.

Instead, Colossal plans to essentially create a hybrid animal, with many of the characteristics of a Tasmanian tiger. Its scientists will use CRISPR gene editing technology to splice bits of recovered thylacine DNA into the genome of a Dasyurid — a family of carnivorous marsupials such as the numbat and Tasmanian devil that are the extinct animal's closest relatives.

The altered nucleus would then be inserted into a Dasyurid egg — and when it develops into an embryo, it would be implanted into a surrogate.

How would the thylacine affect Tasmania's habitat?

"The thylacine was the only apex predator in the Tasmanian ecosystem, so no other animal was able to fill its place once it was lost," Pask said. "We have seen the impacts of this in the Tasmanian devil population which was nearly wiped out by a facial tumor disease."

The return of an apex predator would "remove the sick and weak animals from the population to control the spread of transmissible diseases and also improve the genetic health of all the populations it impacts," he added.

The thylacine played that role for thousands of years, Pask said, and its return now could restore balance to the entire ecosystem in Tasmania.

When might the first embryo be created?

It could arrive as early as the next few years. By comparison, Colossal hopes to bring its first woolly mammoth calves into the world within the next five or six years, using elephant surrogates.

A timeline for the thylacine hasn't been revealed. But Ben Lamm, Colossal's founder and CEO, noted via email that the Tasmanian tiger's expected gestation period of up to 42 days would be much shorter than that of an elephant-mammoth hybrid.

"A large part of our mammoth timeline is based on the nearly two-year gestation of the calves," Lamm said. "I think it is safe to assume that the thylacine proxy could be one of the first animals to be brought back."

Would the Tasmanian tiger ever be brought to mainland Australia?

"Whether we would return the thylacine to the mainland is a really interesting question," Pask said, noting that the animal is believed to have been found in Australia until 2,000 or 3,000 years ago.

"If the thylacine was effective at eradicating some of our invasive pest species such as rabbits, cats and foxes — their reintroduction to the mainland might have major conservation benefits for other ecosystems," he said.

But, he added, such an idea would have to be vetted and studied in captive areas before any broader release could be considered.

Sure, they could — but should they?

Boosting genetic diversity and helping ecosystems are the same reasons Beth Shapiro has cited in speaking in favor of using genetic editing. But while Colossal focuses on trying to bring back extinct animals, Shapiro suggests the focus should be on the wildlife we currently have that are struggling, such as the black-footed ferret (which was once thought to be extinct).

"Maybe we could use this technology to give those populations a little bit of a genetic booster shot and maybe a fighting a chance against the diseases that are killing them," she told NPR in 2017. "We're facing a crisis — a conservation, biodiversity crisis. This technology might be a very powerful new weapon in our arsenal against what's going on today. I don't think we should dismiss it out of fear."

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