From woolly mouse to mammoth

Suddenly, a cute little ball of wool scurries across the table in the biology lab. You are amazed at the sight. This is because the “Colossal Woolly Mouse”, born in October 2024, only resembles mice as we know them to a limited extent. It has been genetically modified so that it has characteristics that could be used to create a woolly mammoth embryo.

The big in miniature: a mouse bred with mammoth fur.

“They're a lot cuter than we thought,” Ben Lamm, co-founder and CEO of Colossal, told USA TODAY. The genetic engineers' goal now is to create a mammoth that can survive in the Arctic and help restore the region's ecosystem.

Born in October 2024, the “Colossal Woolly Mouse” bears only a limited resemblance to mice as we know them.

The researchers compared mouse genes with those found in the mammoth genome. Finally, they altered seven genes of the laboratory mice to breed animals that resembled the phenotypes of the woolly mammoth with dramatically altered coat color, texture and thickness. The genetically modified mice had curly whiskers with wavy, lighter-colored hair that grows up to three times longer with a rough, woolly texture. The mice are also fuller because an altered gene has led to an increase in body weight. And then there is another unintended consequence: they are in demand. “People have asked us if we are going to sell them,” says Lamm.

The next step is to find out whether the mice can cope better with cold than normal mice. If so, these genes would be helpful in the return of the woolly mammoth.

But where did Colossal get the mammoth DNA from? The scientists have analyzed the genetic material of 59 woolly mammoths, Columbian mammoths and steppe mammoths that are between 3,500 and over 1,200,000 years old. The findings are now helping to identify genetic targets for the creation of a next-generation woolly mammoth - effectively a “cold-resistant elephant with all the key biological traits of the woolly mammoth,” the company says on its website. “It will walk like a woolly mammoth, look like one, sound like one, but most importantly, it will be able to inhabit the same ecosystem that was abandoned by the mammoth's extinction,” the geneticists said.

Genes that determine the fur.

The revival attempts are not without controversy. “We must also consider the harm that could result: for example, the suffering of elephant egg donors and surrogate mothers and cloned mammoths with anatomical defects,” write science journalist Emma Marris and Yasha Rohwer, assistant professor of philosophy at the Oregon Institute of Technology, on the website of the Center for Humans and Nature. Ben Lamm replies: “Colossal is consulting with its ethics committee and will follow the protocols of the Institutional Animal Care and Use Committee in future tests”.

“A healthy animal is not one hundred percent guaranteed,” says Christopher Preston, Professor of Environmental Philosophy at the University of Montana. Furthermore, the clone will not be a true woolly mammoth. “So what we're going to bring back is an adapted relative, so basically an Asian elephant that has more hair and better cold tolerance genes,” Preston told USA TODAY.

Original publication:

Chen R et al. (2025)

Multiplex-edited mice recapitulate woolly mammoth hair phenotypes.

BioRxiv. DOI: 10.1101/2025.03.03.641227.