Scientists working to revive the woolly mammoth have accidentally created the cutest mice in the world. Introducing: the Colossal Woolly Mouse. I need at least 10 of these toasted marshmallows in my pocket right now.

Colossal Laboratories and Biosciences announced today that it has created almost 100 living cotton balls by genetically engineering mice to display cold adaptation traits similar to those in woolly mammoths. Such traits include fur which has been significantly altered in colour, texture, and thickness, as evidenced from the prodigious amount of fluff on these squeaky powder puffs.

Yet as cute as these critters are, the Colossal Woolly Mouse’s aggressive adorableness wasn’t the end goal. These mice are just the latest development in Colossal’s quest to “de-extinct” the woolly mammoth. Crucially, the biotechnology company isn’t resurrecting a woolly mammoth from a preserved woolly mammoth cell. Instead, Colossal intends to alter genes from the closely related Asian elephant to create a representative, or proxy, species.

How Colossal created the cutest mice to ever exist

Credit: Colossal Laboratories and Biosciences

To create the woolly mice, Colossal began by analysing 121 mammoth and elephant genomes, including those for Asian and African elephants. Comparing the genomes, the scientists identified the core mammoth genes which they believed were responsible for cold-adaptation traits such as fat metabolism and fur.

Colossal then refined this list to just 10 related genes related to fur and metabolising fat which were also compatible with mice, and used gene editing to modify seven of them in the rodents.

“Since there is more than 200 million years of genetic divergents from woolly mammoths to mice, we decided to look for similar pathways and edits in similar genes to ensure that the edits we were going to make in our our woolly mice would be compatible with life while driving the core genotype to phenotype relationships we were looking for,” Ben Lamm, co-founder and CEO of Colossal Biosciences, told Mashable.

Fat little fuzzballs

The Colossal Woolly Mouse and a normal mouse, next to the Colossal logo.
Credit: Colossal Laboratories and Biosciences

The woolly mouse’s fluffy fur isn’t the only alteration Colossal made. Genes associated with body weight and fat metabolism have also been edited in the mice to better mirror that in mammoths. These changes aren’t as immediately observable as the satisfyingly spherical mice’s fuzzy coats. Colossal’s chief science officer Dr. Beth Shapiro told Mashable that they expect to have more information on the impact on the mice before the end of the year.

“We believe that these changes will impact fat metabolism in response to cold climates,” said Shapiro. “These are experiments that will take some time, because we have to have age matched controls that we can feed different diets and explore behavioural responses to different temperatures.”

Shapiro reports that all of the woolly mice are “happy and thriving,” Colossal advising that the rotund clouds with feet are currently being cared for in a humane, secure facility. Lamm further noted that Colossal’s gene editing hasn’t had any unforeseen consequences on the mice thus far, “except for extreme cuteness which we did not intend for.” 

Credit: Colossal Laboratories and Biosciences

This reported clean bill of health extends to the woolly mice’s reproductive systems, which Colossal says are fully intact and theoretically capable of creating even more of the fuzzballs. Even so, Colossal can’t just allow these palm-sized pom poms to be fruitful and multiply — or at least not yet. The company is currently seeking approval to do so.

“[W]e have submitted to our external ethics panel a request for an amendment to our approved protocol so that we can allow them to breed, which will enable us to do the behavioural experiments to assess the impact of our edits in response to cold,” said Lamm.

Even if Colossal does get approval, it’s unlikely that any of us will ever have one of these tiny tribbles as a ridiculously cute pet. There’s nothing stopping us from dreaming, though.

The mammoth task of de-extinction

A diagram indicating that the creation of the Colossal Woolly Mouse involved editing genes related to a rough coat, curly hair, and lipid metabolism.
Credit: Colossal Laboratories and Biosciences

Genetically engineering miniature sheep for fairies wasn’t Colossal Bioscience’s main agenda. As adorable as the woolly mouse is, its creation is just a step in Colossal’s larger goal of bringing back the woolly mammoth. 

Billing itself as “the world’s first and only de-extinction company,” Colossal is working to modify existing animals to better resemble their extinct relatives, rather than attempt to clone long-gone species. In the case of the woolly mammoth, Colossal hopes to alter an Asian elephant’s genome, as it is the pachyderm’s closest living relative. 

The company aims to deliver its first woolly mammoth calf by the end of 2028, with Lamm stating that they’re on track to have embryos ready in 2026 for a 22-month gestation period. Using mice allows Colossal to test its hypothesis and see the results of their experiments much more quickly, as the average gestation period of a mouse is around three weeks.

“The mouse is validation that our de-extinction pipeline — from genomic analysis, to mapping ancient DNA variants to physical traits, to engineering those genetic edits into an animal and observing the predicted changes — is successful,” said Shapiro. 

Lamm notes that while Colossal is working on multiple parts of its woolly mammoth project in parallel, it’s now mostly in the gene editing phase, having already successfully edited 25 genes in their Asian elephant cells.

“We currently expect to alter around 85 genes in the Asian elephant to de-extinct the core genes and cold-tolerant phenotypes but will know a better exact answer as we get closer to the completion of the project,” said Lamm.

Skepticism about bringing back the woolly mammoth

Two portrait images. On the left is a Colossal Woolly Mouse and a normal mouse being held in someone’s gloved hands. On the right is a Colossal Woolly Mouse on someone’s gloved hand.
Credit: Colossal Laboratories and Biosciences

Despite his and Shapiro’s enthusiasm, there has been significant doubt amongst the scientific community regarding whether Colossal’s ambition to revive extinct species is realistic or beneficial. Ethical concerns have also been raised, including fears that genetic editing could have an unintended detrimental impact on the health of the resultant animals. In 2015, Shapiro herself told NPR that gene editing tools would be better used to save current species than attempt to revive extinct ones, and that she “[didn’t] want to see mammoths come back.” 

Now a decade later, Shapiro appears to have changed her view, and hopes the apparent success of Colossal’s woolly mouse project assuages at least some other people’s concerns as well.

“[W]e only chose genes to edit that we already knew were compatible with healthy mice based on previous work and research,” said Shapiro. “We carefully assessed the efficiency of our editing process and whether there were unintended edits before using cells to make living mice. And we’re doing everything we can to understand the potential impacts of our edits before we move to working with elephants.”

Though she acknowledged that “there are always concerns about technologies that are new or not fully understood,” Shapiro believes that it’s also risky to shun these tools, or refuse to assess they can be used to protect endangered species.

“[I]t is clear that we need to be thinking of new ways to combat the extinction crisis underway today,” Shapiro continued. “As we work toward the goal of a woolly mammoth, we will discover tools that are immediately useful to protect other species from becoming extinct… We can predict the outcome if we continue along the current path, and that is not an outcome that I want to see.”

Why is reviving the woolly mammoth important?

Credit: Colossal Laboratories and Biosciences

Though reviving the woolly mammoth is a mammoth task, Lamm and Shapiro claim that success would have a wider beneficial impact beyond just creating a close-representative of an extinct species. Lamm asserts that Colossal’s work to de-extinct the woolly mammoth has already garnered increased attention and funding for the biodiversity crisis, and that all the technology the company creates is provided to its conservation partners. 

Shapiro further noted that woolly mammoths aerated soil, spread seeds, and removed snow, invigorating tundra ecosystems and increasing biodiversity. Even so, this is an incredibly distant benefit that currently seems unlikely to materialise before climate change threatens or destroys such habitats. It will be many years before Colossal is able to create and breed enough woolly mammoths to make such an impact, assuming this goal is ever achieved at all.

Instead, the greatest potential benefit to reviving the woolly mammoth is likely to be the inspiring impact such an accomplishment would have.

“The mammoth de-extinction project also provides a kind of moonshot goal that inspires people to come together and solve the hard problems that we need to solve in order to save other large megafauna (and smaller animals!) from becoming extinct,” said Shapiro. “It’s also an optimistic story about biodiversity loss, at a time when we really need optimism.”

We’re still far from seeing the first genetically modified woolly mammoth calf take its first steps, and reasonable concerns remain about the endeavour. Yet regardless of your views on Colossal’s woolly mammoth project, the need for more positivity and hope in the world is a sentiment most people can agree with.