The idea of reviving extinct species through genetic engineering may sound like something out of the movies, but scientists are coming closer and closer to making it a reality.

In the 1920s, thylacines, also known as Tasmanian tigers, were slaughtered by European colonizers who believed the tigers were a threat to their livestock.

“It was a human-driven extinction — European settlers came to Australia and brutally obliterated this animal,” said geneticist Andrew Pask from the University of Melbourne to the BBC.

Now, Pask is working with a “de-extinction” company, Colossal Biosciences, to conceive of a way of bringing these animals back.

This process is now closer to being completed due to advances in gene editing technology, such as the Crispr-Cas9. It begins by sequencing an animal’s DNA, which Pask did for the Tasmanian tiger in 2017.

“Our sample was a baby taken from its mothers’ (sic) pouch,” Pask explained. “They shot the mum and immediately dropped the baby into alcohol, which preserves DNA. That was the miracle specimen and the holy grail for us in terms of being able to really build that genome.”

Part of this involves putting together pieces of the DNA that have been lost. Fortunately, the dunnart, a small mouse-sized marsupial, has DNA that is up to 95% similar to the Tasmanian tiger and can provide a blueprint.

Technology was previously unable to complete the process and would not be able to produce an animal that is the exact same. Now, Pask believes that technology has advanced enough to make this possible.

“All of those technologies are in place, but nobody’s done it on this scale before because the DNA-editing technology wasn’t good enough or quick enough,” Pask said. “But now it’s come such a long way that we do have that tech, and we have had significant investment to try and make this work.”

Although Pask is hopeful about the potential for this process, not everyone agrees. Some believe other issues affect this work.

“Many attributes that we have as living animals require several different copies of genes, but it’s not easy to tell from looking at a reconstructed genome how many are needed,” said Michael Archer, a paleontologist at Sydney, Australia’s University of New South Wales.

While the process of bringing extinct animals back has come a long way in recent years, some are concerned about ethics.

As Douglas McCauley, an ecologist at the University of California, Santa Barbara, put it, new advances have raised new questions.

“It is like we’ve just about put the last [stitches in Frankenstein’s monster], and there is this moment of pause as we consider whether it is actually a good idea to flip the switch and electrify the thing to life,” said McCauley.

Pask sees the question more as a matter of deciding which species to resurrect. He contended that not every animal should be brought back to avoid upsetting natural ecosystems.

“I don’t think we should bring all animals back. I think it should have to fit certain criteria,” Pask said.

“For the thylacine it’s a recent extinction event, so its habitat in Tasmania still exists, all the food it used to eat still exists, so there’s somewhere for them to go and they can thrive again in that environment.”

Another sticking point is cost, as it is incredibly expensive to fund the genetic and biological technologies necessary to resurrect an extinct species. Then money would be needed to keep the animals alive.

Some question whether that money would be better used to fund conservation efforts that preserve endangered species.

“There are plenty of species out there on the verge of extinction now that could be saved with the same resources,” explained Joseph Bennett, a conservation biologist at Carleton University in Ottawa who studied the issue from an economics point of view.

But Pask believes the technology could also serve this purpose.

“De-extinction tech isn’t just about bringing back the thylacine, it’s about preventing other animals from becoming extinct,” he said.