Wikimedia Commons

The term “extinct” used to mean gone forever. Now that scientists can use DNA to create embryos, at least in rare instances, a related term has come into use: de-extinction. This means bringing back a species that has left the earth. The Tasmanian tiger may get its chance, according to Australian scientists. They are encouraged by the discovery of a very well-preserved skin brought to light in New Zealand in January 2019. The skin had been preserved some 76 years earlier and was sitting in a drawer without anyone realizing its importance. No guarantees that the DNA from this well-preserved specimen will succeed in creating a new generation of Tasmanian Tigers, but it does give conservationists hope.

The Age of Tasmania tigers

Tasmanian tigers were Australia’s top predatory animal before dingos arrived with humans. Wolf-like, Thylacinus cynocephalus (thylacine) had skeletons similar to dogs and hunted like dogs. But they also carried their young in pouches, same as kangaroos, wombats, and possums. At 45 to 65 pounds, this made them the largest carnivorous marsupial to survive into the modern era. The name came from dark stripes on their backs. About 3,200 years ago, these fierce predators went extinct on the mainland first, probably due to climate change. Somehow the species survived in Tasmania, though, until European colonists arrived and put a bounty on them. The last known thylacine died in captivity in 1936. That’s not that long ago, but few preserved skins remain. A database lists only 78 thylacine skins preserved worldwide in 21 institutional and four private collections.

One important tiger skin

The story of the recently recovered Tasmanian tiger skin combines forgetfulness and the habits of earlier generations. At the turn of the 20th century, bounty hunters went after the tigers and hobbyists collected the preserved pelts. A Whanganui collector, Archie Robertson, scooped up this particular skin in 1923. But somehow it sat forgotten, or at least hidden, in a drawer. It came to light when the house was sold in 1999 and then went on loan to Kahutara Taxidermy Museum. Another couple of decades passed before four Victoria University spotted those distinctive stripes. Now the skin’s been sold to the National Museum of Australia, and hopes are high it will have DNA that could be used for de-extinction.

Former Australian Museum director Mike Archer took part in a related project 19 years ago. The aim that time was to recreate a living Tasmanian tiger using DNA from a pup preserved since 1866. That project was halted in 2005. If this new skin does re-ignite the process, they’ll be using a technique known as “somatic cell nuclear transfer.” It involves putting cells from the skin or bones of an animal that’s gone extinct into the egg of a living relative to form an embryo.

No clones here

Bringing a species like the Tasmanian tiger back from extinction should never be confused with cloning. As Beth Shapiro, an expert in ancient DNA and a biologist at the University of California, Santa Cruz told Smithsonian, that’s a common myth. “Cloning—the process of somatic cell nuclear transfer, which most famously brought us Dolly the Sheep—is a specific technology that requires cells that are harvested from a living individual,” she said. Scientists working on de-extinction use “new molecular tools to edit the genome” and produce a hybrid of sorts, not a clone. Scientists attempting de-extinction on Tasmanian tigers, for example, would insert DNA from this well-preserved skin into cells from the nearest living relative. The Tasmanian devil is the likely recipient. It has an 89 percent match with the thylacine, though it’s smaller than the extinct carnivorous marsupials.

Preventing extinction in the first place

Like any such activities involving DNA manipulation, de-extinction brings ethical dilemmas along with its mission to boost conservation. Even some close to this potential Tasmanian tiger breakthrough object. Otago Palaeogenetics Laboratory director Dr. Nic Rawlence, for example, is an expert on ancient DNA. But he still told Newstalk ZB he “opposed resurrecting extinct species because their spaces in the ecosystem had now been filled by others and research money should go to conserving existing species.”

Other experts say the technology could keep animals from extinction in the first place, at a time when the earth needs all the help it can get. Shapiro gave the example of using genome-editing technology to re-engineer positive traits from extinct rhinos into declining modern-day populations. “De-extinction may not be the answer to the biodiversity crisis that we are facing today, but the technologies that are being developed in the name of de-extinction may become powerful new tools in an active conservation regime,” she said. “Why not provide populations a little bit of genomic assistance so they can survive in a world that is changing too quickly for natural evolutionary processes to keep up?”

The timetable

As for how long it will take for extinct species to start reappearing on earth, according to Shapiro, that depends on your definition. “If you mean a pigeon born with some passenger pigeon traits or an elephant born with mammoth-like traits, it could happen within a few years to a decade,” she said. “If you mean 100-percent mammoth, with all mammoth genes and behaviors, that will never happen.”
And sorry, ‘Jurassic Park’ fans. T-Rex and friends are going to stay extinct. Resurrecting them is “not possible,” Shapiro added. “The limit of DNA survival, which we’d need for de-extinction, is probably around one million years or less. Dinosaurs had been gone for a very long time by then.”