They've got to get out there and eat as much as they can
In the permafrost of Canada's Yukon, the humble habits of arctic ground squirrels — their frantic hoarding, their long hibernations, their sealed and forgotten burrows — have preserved a biological record spanning 700,000 years. Researchers at McMaster University, searching for something far more modest, found instead genetic fragments from woolly mammoths, wolves, and vanished ecosystems, locked in frozen feces like letters never meant to be read. It is a reminder that the archive of life is written in unexpected places, and that the past does not always announce itself through grandeur.
- A routine study of squirrel gut bacteria unexpectedly cracked open a 700,000-year window into Ice Age ecosystems, catching even the researchers off guard.
- The discovery hinges on the squirrels' own biology — eight months of hibernation, frantic hoarding seasons, and burrows that permafrost sealed into accidental time capsules, one even containing a squirrel frozen mid-sleep.
- Scientists reassembled 18 mitochondrial genomes from DNA fragments scattered across the feces, piecing together the evolutionary histories of woolly mammoths, horses, bison, and a cheetah like a shattered mosaic.
- The data is being made publicly available, feeding into de-extinction ambitions — most notably Colossal's project to resurrect the woolly mammoth — though experts caution the result would be a modified elephant, not a true revival.
- A follow-up study on mammoth evolution is already in preparation, with the lead researcher describing the findings only as 'super cool,' suggesting the burrows have not yet given up all their secrets.
In the frozen Yukon, scientists searching for something small found something vast. Tyler Murchie, a paleogenomics researcher at McMaster University, was studying the gut bacteria of arctic ground squirrels when his team discovered ancient DNA embedded in the animals' feces — genetic material from woolly mammoths, wolves, bison, horses, a cheetah, and hundreds of plant species, spanning 700,000 years to as recently as 3,000 years ago.
The preservation owes everything to the squirrels themselves. Awake for only four months a year, they spend that brief season stuffing their burrows with anything they can find. Over millennia, rising permafrost sealed some of those burrows shut, turning them into biological time capsules. One even contained a squirrel frozen mid-hibernation, never to wake.
Murchie was candid about the unglamorous source material, but the science it yielded was anything but. His team reconstructed 18 mitochondrial genomes — including six from woolly mammoths of different eras — by computationally reassembling DNA fragments into coherent genetic portraits of extinct species.
The data will be made publicly available, offering potential fuel for de-extinction efforts like those pursued by Colossal, a U.S. company aiming to resurrect the woolly mammoth. Experts remain measured, noting that any such animal would be closer to a genetically modified Asian elephant than a true mammoth. The deeper questions — philosophical and practical — are still unanswered.
A follow-up study on mammoth evolution is in preparation. For now, Murchie's team has shown that the past can be recovered from the most unlikely of places, and that the Yukon's frozen ground still has more to say.
In the frozen depths of Canada's Yukon territory, scientists have uncovered something unexpected: a biological archive stretching back 700,000 years, preserved not in amber or ice, but in the droppings of arctic ground squirrels sealed inside their own burrows.
The discovery emerged from research that began with a simple question about squirrel microbiomes. Tyler Murchie, a paleogenomics researcher at McMaster University, and his team were studying the gut bacteria of these small rodents when they stumbled onto something far larger. Embedded in the feces were fragments of ancient DNA—genetic material from woolly mammoths, wolves, bison, horses, a cheetah, and hundreds of plant species. The oldest samples dated back 700,000 years; the youngest, just 3,000 years old. It was, Murchie would later say, a "spectacular" find, even if the source material seemed unpromising at first.
The reason this worked at all comes down to the peculiar biology of arctic ground squirrels. These animals are conscious for only about four months each year, spending the remaining eight months in hibernation. During their brief waking season, they become frantic hoarders, stuffing their burrows with everything they can gather—nuts, seeds, leaves, bones, fur, and whatever else lies within reach. Over millennia, some of these burrows became sealed off by rising permafrost, transforming them into perfectly preserved time capsules. One burrow even contained a squirrel itself, frozen in place after settling down for hibernation one season and never waking again.
Murchie acknowledged the unglamorous nature of the discovery. Digging through squirrel feces lacks the romance of unearthing a mammoth tusk. Yet the genetic material told a story that conventional fossils could not. His team reconstructed eighteen mitochondrial genomes from the samples, including six belonging to woolly mammoths that lived in different eras. This involved using computers to reassemble DNA fragments like pieces of a puzzle, each fragment contributing to a larger picture of how these extinct species lived and evolved.
The findings have immediate relevance to one of modern science's most ambitious projects. Colossal, a U.S. company, has publicly stated its intention to resurrect the woolly mammoth, which disappeared roughly 4,000 years ago. The genetic data recovered from the Yukon burrows will be made publicly available, potentially supporting such efforts. Murchie noted, however, that Colossal already possesses extensive genetic material from multiple organisms, so the new data represents only a small addition to what they already have.
Scientific skepticism surrounds the de-extinction goal nonetheless. Experts have pointed out that any animal produced through such efforts would likely be more accurately described as an Asian elephant with genetic modifications to approximate mammoth traits, rather than a true resurrection of the extinct species. The philosophical and practical questions remain unresolved.
Murchie's team is preparing another study that will examine what the recovered DNA reveals about woolly mammoth evolution—details he declined to discuss beyond calling the work "super cool." For now, the squirrel burrows of the Yukon have yielded their secrets, and the scientific community waits to see what stories the ancient DNA will tell.
Citas Notables
I can't believe that we were able to get these insights from squirrel faeces— Tyler Murchie, paleogenomics researcher at McMaster University
La Conversación del Hearth Otra perspectiva de la historia
Why squirrel droppings? Of all the places to find ancient DNA, that seems almost absurd.
It's actually perfect. These squirrels pack their burrows with everything they can find during their four months awake—seeds, bones, fur, plant matter. When permafrost sealed those burrows, nothing could decompose. It's like they were building time capsules without knowing it.
So you're saying the squirrels were doing the preservation work for you?
Exactly. They gathered the material, the permafrost locked it in place, and 700,000 years later, we find woolly mammoth DNA sitting in their stored food and waste. Nature archived itself.
What does reconstructing a mitochondrial genome actually mean? Is that the whole animal?
No, it's a small piece—the DNA from the mitochondria, the cell's energy factory. But even that fragment tells us about evolution, about which mammoths lived when, how they changed. It's like having a single chapter from a book but being able to infer the whole story.
And Colossal wants to use this to bring mammoths back. Do you think that's possible?
The DNA helps, but experts are honest about the limits. You'd end up with something that looks like a mammoth but is genetically mostly elephant. Whether that's "bringing back" the mammoth or creating something new—that's the real question.