Meet what’s probably the fluffiest mouse the world has ever seen. Its fur is long, golden, and wavy, its whiskers curled like the tendrils of a vine. Suffice it to say this is no ordinary rodent. It is a genetically engineered “woolly mouse,” a creature designed to carry traits reminiscent of the woolly mammoth, the Ice Age giant that roamed the Arctic tundra thousands of years ago.

It might not have tusks or weigh five tons, but this altered mouse is considered a major step in a controversial and ambitious plan to bring the woolly mammoth back to life.

The project is the brainchild of Colossal Biosciences, a biotechnology company founded in 2021 to much fanfare (and a lot of tech money). Its goal is using cutting-edge genetic engineering to “de-extinct” species like the mammoth, the dodo, and the Tasmanian tiger. The woolly mouse is supposed to be a proof of concept — a demonstration that Colossal can edit multiple genes at once to produce physical traits associated with extinct animals.

From Mice to Mammoths

In their quest to resurrect the woolly mammoth, Colossal researchers have turned to its closest living relative: the Asian elephant. By comparing the genomes of modern elephants with those of mammoths preserved in permafrost, scientists at Colossal identified key genetic differences that may have allowed mammoths to thrive in cold environments. These include genes related to hair growth, fat storage, and other adaptations to the Arctic.

But testing these genetic changes directly in elephants is impractical. Elephants have a 22-month gestation period and are much harder to manipulate genetically than mice, with which scientists have significant experience tweaking their genomes over countless studies.

Using CRISPR, a powerful gene-editing tool, they targeted ten genes in mice associated with traits like hair length, texture, and fat metabolism. The resulting mice had woolly coats, curled whiskers, and golden fur — traits that echo those of their prehistoric cousins.

“For us, it’s an incredibly big deal,” says Beth Shapiro, chief science officer at Colossal Biosciences, a Dallas company.

The research has not yet been peer-reviewed. The team successfully made up to eight edits simultaneously in seven different genes, which is particularly impressive from a technical standpoint. But the work is far from complete. The next step is to test whether these woolly mice are better adapted to cold environments like their mammoth motifs.

A Mammoth Task Ahead

A woolly mouse is definitely a step forward, but the challenges ahead remain immense. Creating a mammoth-like elephant will require far more than a few genetic tweaks. Scientists will need to identify and edit dozens, if not hundreds, of genes to replicate the mammoth’s size, tusks, and cold tolerance. Then, they’ll have to figure out a way to gestate the modified embryo in a surrogate elephant mother or even in an artificial womb. The logistical hurdles of breeding and raising these hybrid animals could take decades.

There’s also the question of whether the work is of value. Critics argue that the project is a distraction from more pressing conservation efforts. “My overall concern is whether this is a sensible use of resources rather than spending the money on trying to prevent species becoming extinct,” Robin Lovell-Badge, a stem cell biologist at the Francis Crick Institute in London, told The Guardian.

Others point out that no matter how much progress scientists achieve, the resulting animals won’t truly be mammoths but merely some long-haired elephant-mammoth-like hybrids. “You are never going to ‘bring back’ a mammoth,” said Tori Herridge, a paleobiologist at the University of Sheffield. “You are only ever going to create a crude approximation.”

Colossal’s founders, however, see their work as part of a broader mission to combat climate change and biodiversity loss. They argue that reintroducing mammoth-like elephants to the Arctic could help restore the tundra ecosystem, slowing the thaw of permafrost and reducing greenhouse gas emissions.

For now, the woolly mouse is a symbol of both the promise and the pitfalls of de-extinction. It is a reminder that science can achieve remarkable feats, but also that some boundaries — whether ethical, ecological, or biological — are not so easily crossed.