A 216,000-year-old woolly mammoth tooth unearthed in Canada’s Yukon territory has shattered previous assumptions about when these Ice Age giants arrived in North America. Discovered along the banks of the Old Crow River, the fossil is now confirmed to be the oldest known specimen of a woolly mammoth (Mammuthus primigenius) on the continent, predating earlier estimates by over 100,000 years.
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The find was announced in a study published April 9, 2025, in the journal Molecular Biology and Evolution. It provides the first physical evidence that woolly mammoths roamed North America far earlier than previously believed.
A Rare and Remarkable Find
Camilo Chacón-Duque, a researcher at the Centre for Palaeogenetics at Stockholm University and lead author of the study, described the discovery as highly unusual. “Most North American mammoth specimens of this age likely belong to other species that existed before woolly mammoths,” he said. “To our knowledge, the Old Crow mammoth is the oldest North American mammoth fossil that can be morphologically identified with confidence as a woolly mammoth.”
Prior to this discovery, scientists believed woolly mammoths crossed into North America from Siberia between 120,000 and 10,000 years ago. However, this specimen pushes that timeline back significantly and offers concrete evidence supporting older, previously unconfirmed genetic models suggesting mammoth migration began much earlier.
Unlocking Deep-Time DNA
Beyond the fossil’s age, its preserved DNA offered a rare opportunity to examine the genetic heritage of mammoths. Extracted as part of a broader study on mammoth genetics, the tooth revealed long-lost genetic diversity across multiple mammoth lineages over a million-year timespan.
While the Old Crow mammoth’s DNA is not the oldest in the study—samples from Russia date back as far as 1.3 million years—it belongs to the oldest group in the North American dataset. Researchers analyzed 34 newly collected DNA samples along with over 200 previously studied ones from across the Northern Hemisphere, mainly from Siberia and North America.
The team focused on mitochondrial genomes, which are passed from mothers to offspring, to better understand lineage and migration. They used a combination of radiocarbon and molecular clock dating to determine the age of each sample. Because radiocarbon dating is only reliable up to around 50,000 years, molecular clock techniques—based on the mutation rates of genes—were refined for older samples.
A “Eureka” Moment in Dating
Chacón-Duque described the successful molecular dating of the Old Crow sample as a “eureka moment.” After months of fine-tuning dating methods, the DNA-based estimate perfectly matched geological data from the rock layers where the tooth was found. The researchers also improved accuracy by dating samples individually rather than in groups, a departure from previous methodologies. “We built upon previous methodologies and carefully fine-tuned these to get more reliable age estimates,” Chacón-Duque said.
Mammoths on the Move
The study also contextualizes woolly mammoths within the broader narrative of mammoth evolution. Mammoths first evolved in tropical Africa and gradually migrated into Eurasia and eventually North America. Columbian mammoths (Mammuthus columbi), which crossed into North America around 1.5 million years ago, were already present long before the arrival of their woolly cousins. These Columbian mammoths were typically larger, standing up to 13 feet tall compared to the woolly mammoth’s 11 feet.
While previous studies based on modeling or genetic inference hinted at earlier woolly mammoth arrivals, the Old Crow specimen is the first physical fossil to prove their presence on the continent more than 200,000 years ago.
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The genetic data also revealed how climate cycles shaped mammoth diversity. During warm periods, mammoth populations appear to have contracted into isolated refugia, expanding again during colder glacial phases. This pattern highlights the species’ adaptability but also its vulnerability to climate change. Most mammoths died out around 10,500 years ago at the end of the last Ice Age, as the planet warmed. Some isolated populations, including on islands in Alaska and Siberia, survived for several thousand years longer—until around 4,000 years ago.