Tiny lab mice just got a mammoth-sized upgrade — genetic tweaks have given them thick, woolly fur, bringing science one step closer to reviving traits of extinct species.
Texas-based bioengineering company Colossal Biosciences on Tuesday announced the birth of what it calls the “woolly mouse,” a genetically engineered rodent with key mammoth-like traits.
Its thick, textured coat, reminiscent of a woolly mammoth’s, could help it adapt to colder climates, the company said.
Woolly mammoths roamed the frozen tundras of Europe, Asia and North America for more than 300,000 years before going extinct around 4,000 years ago.
The Ice Age icons had two huge tusks and a thick layer of shaggy, chocolate-brown hair.
Since 2021, Colossal has been working on a plan to revive the woolly mammoth and later the dodo bird. To do this, the company has focused on identifying key traits of extinct animals by studying ancient DNA, intending to genetically engineer them into living animals.
And that’s where the woolly mouse comes in.
In this February 2025 photo provided by Colossal Biosciences, a genetically edited mouse with long, thick, woolly hair at a lab in Dallas, Texas.
(Colossal Biosciences via AP)
“The Colossal Woolly Mouse marks a watershed moment in our de-extinction mission,” Ben Lamm, co-founder and CEO of Colossal Biosciences, said in a media release.
“By engineering multiple cold-tolerant traits from mammoth evolutionary pathways into a living model species, we’ve proven our ability to recreate complex genetic combinations that took nature millions of years to create. This success brings us a step closer to our goal of bringing back the woolly mammoth.”
Colossal said it focused on mice first to confirm whether the process works before potentially moving on to edit the embryos of Asian elephants, the closest living relatives to woolly mammoths.
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Results were posted online, but they have not yet been published in a journal or vetted by independent scientists.
The making of the ‘woolly mouse’
To create their woolly mice, Colossal Biosciences studied 121 mammoth and elephant genomes to identify genes linked to traits like thick fur and cold adaptation.
They focused on 10 genes related to hair length, texture and colour, plus fat metabolism. Using advanced gene-editing technologies, they made eight edits in the mouse genome, targeting seven specific genes.
The result? Mice with hair three times longer than normal, and a woolly texture, wavy coats and curled whiskers.
It’s the first living animal engineered to express cold-adapted traits from mammoth genes, the company said, adding it could serve as a valuable model for studying how mammals adapt to cold climates.
“The Colossal Woolly Mouse demonstrates remarkable progress we’ve made in precise genome engineering, including optimized delivery methods, innovative multiplexing and combinations of gene targeting strategies,” George Church, professor of genetics at the Wyss Institute and Harvard Medical School and Co-founder of Colossal, said in a media release.
“We are showing that we can now rationally design and construct complex genetic adaptations, with profound implications for the future of multi-gene de-extinction and engineering.”
Colossal said it focused on mice first to confirm whether the process works before potentially moving on to edit the embryos of Asian elephants, the closest living relatives to woolly mammoths.
Colossal Biosciences via AP
What the science community is saying
Some independent experts are skeptical about the concept of de-extinction, with mixed opinions on whether this approach will benefit conservation efforts.
“You’re not actually resurrecting anything — you’re not bringing back the ancient past,” Christopher Preston, a wildlife and environment expert at the University of Montana, who was not involved in the research, told The Associated Press.
“You might be able to alter the hair pattern of an Asian elephant or adapt it to the cold, but it’s not bringing back a woolly mammoth. It’s changing an Asian elephant.”
Still, the refinement of precision gene-editing in animals could have other uses for conservation or animal agriculture, said Bhanu Telugu, who studies animal biotechnology at the University of Missouri and was not involved in the new research.
Telugu told The Associated Press he was impressed by Colossal’s technological advances that enabled scientists to pinpoint which genes to target.
Colossal is not the first group to take aim at resurrecting the mammoth through gene editing. The California-based Revive & Restore Project also wants to see the woolly mammoth brought back to life.
Scientists have toyed with the idea of resurrecting mammoths for years, in large part because there are so many well-preserved bodies left over in the Russian permafrost. Those bodies are rich with various tissues and DNA, unlike the remains of dinosaurs, which typically turn to stone through the fossilization process.
— with files from Global News and The Associated Press
