Scientists modify mice genes to grow thick mammoth-like fur

Scientists modify mice genes to grow thick fur like woolly mammoths — Genetically edited mice with long, thick, woolly hair at a lab in Dallas, Texas, U.S., February 2025. Photo: Colossal Biosciences/via AP

DALLAS, — Scientists at Colossal Biosciences, a biotechnology company, have announced new developments in their attempt to genetically modify living animals to resemble extinct species, such as the woolly mammoth.

The company’s breakthrough includes editing the genes of mice to produce animals with thick, woolly fur, similar to that of the long-extinct mammoth, which roamed Europe, Asia, and North America until around 4,000 years ago.

The company, which gained attention in 2021 for its plan to bring the woolly mammoth back to life, now focuses on identifying and replicating key genetic traits of extinct species. CEO Ben Lamm stated that the objective is to “incorporate these traits into living animals” through the study of ancient DNA.

Colossal’s announcement on Tuesday revealed its success in editing seven genes in mice embryos, resulting in mice with dense, fur-covered bodies.

The genetically engineered animals, referred to as “Colossal woolly mice,” have not yet been published in a scientific journal and have not undergone independent peer review.

Experts outside Colossal have expressed mixed opinions about the project’s potential impact on conservation efforts. Christopher Preston, a wildlife expert at the University of Montana, said that while the research is fascinating, it does not bring back extinct animals, but rather modifies living species. “It’s not resurrecting the past,” Preston explained.

Vincent Lynch, a biologist at the University of Buffalo, acknowledged that the research was “technologically impressive.” Lynch noted that while genetic engineering in mice has been a common practice since the 1970s, advances in gene-editing tools like CRISPR have made the process more efficient.

Colossal’s team selected traits linked to hair texture and fat metabolism in order to increase cold tolerance, a key feature of woolly mammoths, which survived in the Arctic’s frigid conditions.

The company’s chief scientist, Beth Shapiro, explained that these traits already exist in some living mice, but Colossal has combined them into a single mouse.

The company’s primary focus with the woolly mice is to test its gene-editing techniques before attempting similar modifications to Asian elephants, the closest living relatives of the woolly mammoth.

However, Lamm acknowledged that working with Asian elephants—an endangered species—will involve regulatory challenges.

Independent scientists remain cautious about the concept of “de-extinction.” Preston stressed that altering an Asian elephant’s appearance or cold tolerance does not equate to resurrecting a woolly mammoth, but rather adapting the existing species.

Despite this, experts like Bhanu Telugu, a researcher at the University of Missouri, see promise in the potential applications of precision gene-editing for conservation and agriculture.

Colossal’s work may eventually benefit human health, as the company has also launched two healthcare subsidiaries. According to Lamm, these advancements are part of Colossal’s broader business strategy to monetize their technology.

(With files from AP)