Scientists say they’re a step closer to reviving mammoths. What could go wrong?

A company aiming to bring extinct animals back from the dead said it has taken an elephant-sized step toward genetically resurrecting the woolly mammoth, a wild if contentious goal to repopulate the Arctic tundra with a missing titan.

Colossal Biosciences, a biotechnology company based in Dallas, announced Wednesday it has produced a line of Asian elephant stem cells that can be coaxed to transform into other types of cells needed to reconstruct the extinct giant - or at a least a mammoth-like elephant designed to thrive in the cold.

“It’s probably the most significant thing so far in the project,” said George Church, a Harvard geneticist and Colossal co-founder. “There are many steps in the future.”

For proponents, bringing back vanished animals is a chance to correct humanity’s role in the ongoing extinction crisis. Breakthroughs in their field, they say, may yield benefits for animals still with us, including endangered elephants.

Yet the technical challenges of birthing into the world a living, breathing mammoth remain, well, colossal. And the project raises hairy ethical questions: Who decides what comes back? Where will the reborn species go? Could the money be better spent elsewhere? And how hard will “de-extinction,” as the revival efforts are known, be on the animals themselves?

“The lack of knowledge is the thing that worries me about the welfare of animals,” said Heather Browning, a philosopher at the University of Southampton in England and a former zookeeper.

Can we really bring back the mammoth?

During the last ice age, the woolly mammoth owned the top of the world, plodding across Eurasia and North America and as far south as the modern-day Midwest.

As the creatures died out 4,000 years ago, some carcasses froze over in icy tundra that preserved not only their bones but also their flesh and fur, giving paleontologists the chance to collect DNA fragments. Some mammoth meat was so well kept that at least one adventurous researcher has eaten it.

By 2015, scientists sequenced its genetic blueprint well enough to offer a potential manual for remaking a mammoth. But to test what exactly each of these genes do - which give the beast their curved tusks, fatty build and, of course, thick fur - Church wants elephant stem cells in which he could engineer mammoth DNA and grow tissue samples.

Scientists have produced such stem cells in the lab for other animals, including humans, mice, pigs and even rhinos. But for years, getting the right elephant stem cells to test all those cold-climate characteristics proved elusive, in part because elephant cells’ ability to avoid cancer made reprogramming them difficult.

Colossal said they have produced the stem cells they need by suppressing the anti-cancer genes and bathing the cells in the right chemical cocktail. Colossal published a preprint Wednesday that is not yet peer-reviewed. The company said it is working to place the study in a peer-reviewed scientific journal.

“It hasn’t been straightforward,” said Eriona Hysolli, the company’s head of biological sciences. “It hasn’t been immediately obvious. There were a lot of innovations along the way.”

Eventually, the company wants to genetically edit a nucleus of a stem cell with mammoth genes and fuse it into an elephant egg. From there, if everything goes according to plan - still a big if - they will implant the embryo in an elephant surrogate and wait for it to give birth.

Even if we can, should we?

Matthew Cobb, a zoologist at the University of Manchester in England, said all those “ifs” may be insurmountable. There is no guarantee that the modified chromosomes can be introduced to an elephant cell, or if that an embryo will take hold in an elephant womb.

And perhaps more profoundly, there is the question of how a mammoth, if born, will learn to behave like a mammoth. “Most of the mammals and birds that are being talked about have complex social and cultural interactions that have been lost,” Cobb said. “They are not simply their genes.”

Modern elephants, for instance, are highly social beings, passing down knowledge about the location of watering holes and other survival skills from one generation to the next. Their ancient cousins may be similar. “They’ve got no elders to raise them, to teach them,” Browning said. “They’re got no way of learning how to be mammoths.”

And any living surrogate elephant meant to gestate and give birth to a new mammoth will go through some degree of hardship. “How many dead elephants are we willing to have to get one woolly one?” said Tori Herridge, a paleobiologist specializing in ancient elephants.

Colossal said its long-term goal is to use artificial wombs to gestate the animals, itself a tall technological task. The company notes that its research into elephant cells can help with current conversation efforts, such as potential treatments for a form of herpes that kills young elephants. Indeed, the company hopes to make money by licensing or selling some of the technologies it creates along the way.

“It’s not so much bringing back the mammoth, it’s saving an endangered species,” Church said. “It’s working out technology that’s useful for conservation and climate change.”

But Cobb said the biggest threats facing elephants are hunting, habitat destruction and other conflicts with humans. “How will a greater understanding of cell biology help?”

What if they go extinct again?

One of Colossal’s overarching arguments for bringing back the mammoth is climate change. Scientists at the company say future Arctic herds can stomp down permafrost and prevent more of it from thawing and releasing atmosphere-warming carbon into the air.

“They’re a lot of reasons to restore that environment to what it was,” Church said. “This is the keystone species that’s missing for that.”

Then there is this philosophical question: Is a bioengineered mammoth truly a mammoth? Or is it a furrier elephant that can tolerate the cold?

“It’s a completely new organism that’s being created,” Herridge said. She added that it is still an open question as to what killed off the woolly mammoth: Was it humans overhunting them, or the natural end of the last ice age? If the answer is the latter, then the Arctic may be unsuitable for the resurrected creature, whatever you want to call it.

“I would love to see a mammoth alive,” she said. “I would absolutely love to have a time machine where I could go back to the ice age, and I could see a herd of mammoths being mammoths in the landscape in which they evolved.”

“But all of that has gone.”