Even the most ordinary traces of life can hold extraordinary stories
Beneath the frozen Yukon, the humble droppings of ancient ground squirrels have preserved a genetic chronicle spanning 700,000 years — a reminder that the most unassuming remnants of life can carry the deepest memory. Researchers from McMaster University, the Hakai Institute, and the University of Alberta have recovered DNA from over 200 plant species and iconic megafauna like woolly mammoths, reconstructing vanished worlds with a fidelity that bones alone could never offer. In studying how ecosystems rose and fell across deep time, science finds not only a record of the past, but a lantern for navigating the climate uncertainties ahead.
- Frozen squirrel burrows in Canada's Yukon have yielded one of the richest ancient DNA archives ever found, containing genetic traces of entire ecosystems stretching back 700,000 years.
- The discovery upends long-held assumptions — a squirrel lineage once native to the Yukon no longer exists there, its closest living relatives now found in western Siberia, revealing dramatic population shifts driven by ancient climate change.
- Permafrost preserved what bones and soil could not, but that same permafrost is now thawing, placing these irreplaceable biological records under urgent threat of permanent loss.
- Scientists developed new extraction techniques to recover high-quality DNA from material once considered too degraded to study, pushing the boundaries of paleogenomics into previously unreachable depths of time.
- The research, conducted with the blessing of the Tr'ondëk Hwëch'in First Nation, now points forward — offering a framework for understanding which species may survive today's climate crisis and which may not.
Buried in the permafrost of Canada's Yukon, ancient ground squirrel droppings have become one of the most remarkable scientific archives ever discovered. Researchers from McMaster University, the Hakai Institute, and the University of Alberta spent years extracting genetic material from these frozen burrows, recovering DNA from more than 200 plant species, insects, microbes, and megafauna — including woolly mammoths, steppe bison, and wolves — along with 18 complete mitochondrial genomes.
The secret lies in the squirrel's own habits. These small burrowing animals gathered seeds, plants, and animal remains from across the landscape and brought them home, leaving behind waste that accumulated into a layered biological record. The cold, stable permafrost slowed decay to nearly nothing, preserving fragile genetic material far better than bones or surrounding soil ever could.
What emerged was a portrait of a lost world — the mammoth steppe, rich with grasses and flowering plants, teeming with large animals. But the findings also surprised researchers: one squirrel lineage dating back 700,000 years has vanished from the Yukon entirely, its closest relatives now living in western Siberia. The animals had moved with their habitats as climates shifted, challenging the assumption that today's regional species were simply ancient ones in place.
By tracking DNA across different time periods, scientists could follow how ecosystems transformed — from open grasslands to forests of spruce and birch — and how species adapted, migrated, or disappeared along the way. Hendrik Poinar of McMaster University noted that the research illuminates not only ancient extinctions but the dynamics of survival itself, offering lessons directly applicable to conservation in a warming world.
The study was conducted with permission from the Tr'ondëk Hwëch'in First Nation, on whose traditional lands the research took place. Many burrows remain unexplored, but as permafrost thaws, these biological records face permanent loss — lending the work a quiet urgency that extends well beyond the laboratory.
Buried beneath the frozen ground of Canada's Yukon, in burrows sealed away for hundreds of thousands of years, lie small pellets of ancient squirrel droppings. These unremarkable-looking deposits have become one of the richest sources of ancient DNA ever recovered, offering scientists an unprecedented window into ecosystems that vanished long before humans walked the Arctic.
Researchers from McMaster University, the Hakai Institute, and the University of Alberta spent years analyzing samples extracted from these permafrost burrows, where the cold had preserved biological material in stunning detail. What they found was extraordinary: genetic traces of entire vanished worlds, stretching back as far as 700,000 years. The droppings contained DNA from more than 200 plant species, insects, microbes, and large animals—including woolly mammoths, horses, steppe bison, wolves, and ancient predators. The samples also yielded 18 complete mitochondrial genomes, each one a genetic snapshot of a creature that once roamed the Arctic landscape.
The key to this discovery lies in the behavior of the Arctic ground squirrel, a small burrowing animal that hibernates for months each year. These squirrels gather seeds, plants, and small animal remains from the surrounding landscape and bring them back to their burrows, where they store food and leave behind waste. Over millennia, as these burrows remained frozen and undisturbed, they accumulated a natural archive of biological material. Tyler Murchie of the Hakai Institute explained the mechanism simply: the squirrels went out into the landscape, collected bits of plant material, bones, and seeds, and brought everything back to their burrow. That varied diet—fungi, small animals, seeds, flowering plants—meant their droppings contained genetic material from dozens of different sources, each one a clue to what the ancient environment contained.
The research revealed a landscape far different from the Arctic tundra of today. The mammoth steppe, as scientists call it, was dominated by grasses and flowering plants that supported a thriving megafauna. But the study also uncovered something unexpected: genetic diversity among the ground squirrels themselves suggested that populations had shifted dramatically over time. One lineage dating back 700,000 years no longer exists in the Yukon. Its closest living relatives now inhabit western Siberia, indicating that as climates changed and habitats moved, the animals moved with them. This finding challenged the long-held assumption that the squirrels living in the region today were the same species as those from hundreds of thousands of years ago.
What surprised researchers most was how well the DNA survived. The permafrost's cold, stable conditions slowed decay to a near halt, preserving fragile genetic material better than bones or surrounding soil samples. The team developed specialized extraction and analysis methods to recover high-quality genetic information from samples hundreds of thousands of years old—material that would normally be too damaged and fragmented to study. The result was a detailed genetic record of how ecosystems transformed over deep time. As the region shifted from open grasslands to forests of spruce and birch, those changes were reflected in the DNA preserved within the droppings. By comparing samples from different periods, scientists could track how species adapted, migrated, or disappeared as the climate shifted.
Hendrik Poinar of McMaster University emphasized the broader significance: the research helps reconstruct paleoenvironments from much deeper in time, providing insights into how megafauna evolved, dispersed, and ultimately went extinct. But the implications extend beyond ancient history. By studying how ecosystems responded to past climate changes, scientists hope to better understand what may happen as the planet warms today. Understanding which species survived dramatic shifts and which did not could guide modern conservation efforts and help identify which animals are most vulnerable to environmental change. The techniques developed for this research can also be applied to other environments, expanding the scope of paleogenomics research and potentially unlocking new discoveries about human history, biodiversity, and evolution.
The work was conducted with permission from the Tr'ondëk Hwëch'in First Nation, whose traditional lands include the study area. Researchers believe many more burrows remain unexplored across the Yukon and beyond, each one potentially holding additional details about ancient life. As permafrost thaws due to climate change, these biological records may be lost forever, making the preservation of Arctic environments increasingly urgent. In the end, these small pellets offer a powerful reminder: even the most ordinary traces of life can hold extraordinary stories about the past.
Notable Quotes
Ground squirrel coprolites preserve remarkably diverse genetic snapshots of ancient Beringia, offering insights into how ecosystems responded to drastic climatic shifts.— Hendrik Poinar, McMaster University
The squirrels go out into the landscape, collect bits of plant material, bones, and seeds, and bring everything back to their burrow, creating a natural archive of biological material.— Tyler Murchie, Hakai Institute
The Hearth Conversation Another angle on the story
How does a squirrel dropping end up preserving DNA better than bone?
The permafrost does the work. It's so cold and stable that decay basically stops. Bone gets broken down by microbes and chemical processes, but in frozen ground, nothing moves. The squirrel's burrow becomes a sealed vault.
So the squirrel is just a collector, really. It goes out, eats things, and brings them home.
Exactly. It's gathering seeds, plants, small animals—whatever it can find. Then it deposits all that genetic material in one place. Over thousands of years, you get layers of these droppings, each one a snapshot of what was alive at that moment.
The fact that one squirrel lineage from 700,000 years ago is now only found in Siberia—what does that tell us?
It tells us the climate was the driver. As the world warmed and cooled, the animals moved. The landscape changed from grassland to forest, and the species that couldn't adapt either shifted their range or disappeared. It's a record of survival and migration written in genes.
And you think this helps us understand what's happening now?
It has to. We're watching species respond to warming in real time, but we don't have a long historical record of how they've coped before. This gives us that record. We can see which traits were selected for under climate stress, which populations were resilient. That's invaluable.
What happens to all these burrows as the permafrost melts?
They're lost. The DNA degrades. The archive disappears. That's why the urgency is real—there's a window closing on understanding these ecosystems before the evidence literally thaws away.