The Oldest North American Woolly Mammoth Has Been Discovered In Ancient DNA
A 216,000-year-old tooth found along the Old Crow River in the Yukon territory in Canada has confirmed that woolly mammoths arrived in North America at least 100,000 years earlier than previously believed.
Researchers from Stockholm University in Sweden extracted DNA from the Old Crow mammoth fossil as part of an extensive analysis of mammoth genetics.
They revealed the existence of “long-lost” genetic diversity from different lineages across a million years of mammoths’ evolutionary history.
The ancestors of mammoths evolved in tropical Africa. They were closely related to living elephants. Then, the ancestors began moving into the Northern Hemisphere around three million years ago. They adapted to life in the cold and spread out.
The researchers analyzed 34 new mammoth mitochondrial genomes to learn more about mammoth evolution. The new samples came from mainly Siberia and North America.
Most of the samples were less than 50,000 years old. For the older samples, the team developed fresh techniques like DNA-based age estimates to date them accurately.
The first mammoths arrived in North America long before the Old Crow mammoth. The earliest were the Columbian mammoths.
They descended from mammoths in Eurasia. Around 1.5 million years ago, they crossed a piece of land that once stretched from eastern Russia to North America.
According to the National Park Service, Columbian mammoths could grow up to roughly 13 feet tall, while woolly mammoths reached a height of around 11 feet. Woolly mammoths first evolved in eastern Siberia some 700,000 years ago. Later, they spread to North America.
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A popular theory posed that woolly mammoths crossed between Siberia and Alaska 120,000 to 10,000 years ago, but researchers have since found older evidence of their arrival.
“Other studies using genetic inferences or modeling have suggested the presence of mammoths as far back as 400,000 years, but Old Crow confirms with a physical specimen that mammoths indeed had a longer presence in the American continent than initially expected, at least >200,000 years,” said Camilo Chacón-Duque, the lead author of the study and a researcher at the Center for Paleogenetics at Stockholm University.
Overall, the research points to major mammoth lineages originating in ancient Siberia. It also demonstrated how climate affected mammoth diversity over time. During cold periods and the beginning stages of glacial periods, mammoth diversity seemed to spread.
By the end of the last ice age, the majority of mammoths died out around 10,500 years ago as the world became warmer.
Some isolated populations of woolly mammoths on islands managed to persist in Alaska and Siberia for a few thousand more years, but the last of them finally went extinct about 4,000 years ago.
The details of the new study were published in the journal Molecular Biology and Evolution.
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