In the ever-evolving field of genetic engineering, even the tiniest breakthroughs can pave the way for colossal change. That’s precisely what Colossal Biosciences hopes to achieve with its latest development—the creation of the world’s first “woolly mice”, a genetically modified species engineered to grow thick, mammoth-like fur.
These fluffy, long-haired rodents might not look like much, but according to Colossal, they represent a significant step toward resurrecting the woolly mammoth, a species that vanished from Earth thousands of years ago. By successfully manipulating key mammoth genes in mice, the company believes it has validated the genetic modification pipeline needed to one day bring back the extinct giants.
Colossal’s scientists began by comparing woolly mammoth DNA to modern elephants, which share 95% of their genome with their ancient relatives. Through this analysis, they identified key genes responsible for the mammoth’s thick fur, wavy coat, and cold-weather adaptations.
The next step? Testing those genes on mice.
Using CRISPR and other gene-editing tools, the team made eight targeted genetic modifications to fertilized mouse embryos, then implanted them into surrogate mothers. The result? A new breed of mice with thicker, longer, and wavier coats—traits that mirror those found in woolly mammoths.
Dr. Beth Shapiro, Colossal’s chief science officer, calls the success a major proof of concept for the company’s larger de-extinction efforts. “The mouse is validation that our de-extinction pipeline is successful,” she told MailOnline.
If everything goes according to plan, Colossal hopes to engineer the first mammoth-elephant hybrid embryos by the end of 2026, with the first calves expected by 2028. The company’s ultimate goal is to reintroduce herds of mammoths to the Arctic tundra, where they believe the animals could help slow climate change by knocking down trees and maintaining grasslands that reflect more sunlight, keeping permafrost frozen.
But not everyone is convinced.
Critics argue that while modifying mice is a useful first step, translating these changes to elephants will be a far greater challenge. Elephant pregnancies last nearly two years, and the species has low reproductive success with artificial reproductive technology, making large-scale breeding efforts slow and difficult.
Professor Dusko Ilic of King’s College London raises a crucial question: “How many elephant cows would need to undergo experimental pregnancies to give birth to a ‘woolly elephant’? And how long would it take before the first such hybrid is born?”
Others question whether releasing mammoths into the wild is scientifically or ethically responsible. Unlike rewilding efforts with bison or beavers, no modern ecosystem has had to accommodate woolly mammoths for thousands of years. There’s no precedent for what might happen if they were reintroduced.
Even Colossal’s own CEO, Ben Lamm, admits there’s no way to be 100% certain of the environmental impact. However, he insists that careful study and controlled reintroduction efforts will ensure any risks are minimized.
