A sealed vial of sediment pulled from Yukon permafrost doesn’t seem like much of an accomplishment. It looks like dirt until the sequencing results arrive. Inside it, scientists from institutions including McMaster University and the University of Alberta have found genetic traces of mammoths, horses and predators that have not roamed the Arctic for tens of thousands of years.
The material was not bone or tooth enamel. It has been fossilized droppings of an Arctic ground squirrel preserved in ice for up to 700,000 years.The study, published in the journal Nature Communications, titled “Ground squirrel squirrels preserve complex archives of ancient environmental DNA over 700,000 years,” forces us to rethink what counts as a viable fossil record. In practical terms, this represents a technological breakthrough in paleontology: using ancient environmental DNA trapped in coprolites to reconstruct entire food webs that once existed in Beringia.
How squirrel poop preserved DNA from mammoths, wolves and hundreds of ancient plants
The arctic ground squirrel (Arctic ground squirrel) doesn’t just leave droppings behind. It leaves behind a compressed snapshot of its environment. These squirrels feed widely, including plants, fungi, insects, and sometimes carrion, and they also store material within burrows that remain sealed in the permafrost for thousands of years. In state-of-the-art sequencing laboratories, researchers have recovered more than 18 mitochondrial genomes from specimens, including woolly mammoth, steppe bison, and horse subspecies.
They also identified DNA signatures of wolves and big cats, including cougar or cheetah predators, and more than 200 plant groups spanning multiple glacial periods dating back approximately 30,000 to 700,000 years ago.What makes this possible is not just cold preservation, but accumulation. Each pellet contains environmental DNA from whatever the animal has interacted with, whether ingested, inhaled or collected in its burrow.
It turns a single biological sample into a multiplexed environmental record.
What do 700,000-year-old coprolites tell us about predator-prey and plant relationships?
Bones preserve anatomy, teeth preserve diet, coprolites, fossilized feces, preserve interaction. This distinction is why this work has attracted attention across paleontology. A bone confirms the presence of a mammoth in the area. Squirrel droppings can show what these mammoths coexisted with, what they ate indirectly through plant chains, and which predators were moving across the same landscape.Tyler Murchie of the Hakai Institute, lead author on the study, described squirrels as natural collectors. This analogy is useful because the burrow acts like a low-temperature archive with stable humidity, little microbial activity, and rapid burial in permafrost layers that slow DNA degradation.At the molecular level, the maintenance of mitochondrial DNA flexibility and the protective effect of low-oxygen frozen conditions depend.
Over time, enzymatic decomposition slows dramatically, allowing the parts to remain recoverable long after most of the organic matter is gone.
What ancient DNA is rewriting about Arctic species persistence over 700,000 years
One of the most important findings is not the species list but the mismatch between putative continuity and genetic turnover.For many years, Arctic paleontology assumed that fossil ground squirrel remains represented a single long-lived subspecies in the Yukon. Genetic data complicates this picture. Researchers have identified a previously unknown diversity, including a lineage dating back nearly 700,000 years with modern relatives in western Siberia. Evolutionary geneticist Hendrik Poinar, director of the McMaster Center for Ancient DNA, noted that genomic regions under selection during past climate shifts may help inform models of how modern species respond to current warming trends.
The main limitation in ancient DNA research is fragmentation over time. Most usable sequences decay after about 100,000 years under typical conditions. These samples extend beyond this limit.
