Indigenous Americans, who include Alaska Natives, Canadian First Nations, and Native Americans, descend from humans who crossed an ancient land bridge connecting Siberia in Russia to Alaska tens of thousands of years ago. But scientists are unclear when and where these early migrants moved from place to place. Two new studies shed light on this mystery and uncover the most closely related Native American ancestor outside North America.
In the first study, researchers led by Eske Willerslev, a geneticist at the University of Copenhagen, sequenced the whole genomes of 34 individuals who lived in Siberia, the land bridge Beringia, and Alaska from 600 to nearly 32,000 years ago. The oldest individuals in the sample—two men who lived in far northern Siberia—represent the earliest known humans from that part of the world. There are no direct genetic traces of these men in any of the other groups the team surveyed, suggesting their culture likely died out about 23,000 years ago when the region became too cold to be inhabitable.
Elsewhere on the Eurasian continent, however, a group arose that would eventually move into Siberia, splinter, and cross Beringia into North America, the DNA analysis reveals. A woman known as Kolyma1, who lived in northeastern Siberia about 10,000 years ago, shares about two-thirds of her genome with living Native Americans. “It’s the closest we have ever gotten to a Native American ancestor outside the Americas,” Willerslev says. Still, notes Ben Potter, an archaeologist at the University of Alaska in Fairbanks who was not involved with the work, the relation is nevertheless distant.
Based on the time it would have taken for key mutations to pop up, the ancestors of today’s Native Americans splintered off from these ancient Siberians about 24,000 years ago, roughly matching up with previous archaeological and genetic evidence for when the peopling of the Americas occurred, the team reports today in Nature.
Additional DNA evidence suggests a third wave of migrants, the Neo-Siberians, moved into northeastern Siberia from the south sometime after 10,000 years ago. These migrants mixed with the ancient Siberians, planting the genetic roots of many of the area’s present-day populations.
The results are exciting, if a bit unsurprising, says Connie Mulligan, an anthropologist at the University of Florida in Gainesville. “To me, it makes total sense that there were a lot of populations migrating through the region and replacing each other, with some of them moving into the Americas.”
In the second study, led by biologist Pavel Flegontov at the University of Ostrava in the Czech Republic and also appearing today in Nature, Potter and colleagues attempt to uncover the roots of a genetic family known to scientists as Paleo-Eskimos (although this term is disputed by Indigenous groups themselves). Archaeological records suggest the ancestors of these individuals moved into modern-day Alaska and the Canadian Arctic about 5000 years ago, but how they relate to modern groups remains a mystery.
The scientists analyzed the genomes of 48 ancient individuals from sites in the North American Arctic and Siberia dating from between about 7000 to 300 years ago. They then compared their DNA to those of other modern and ancient Indigenous people across northern North America and looked for patterns in shared ancestry and language families.
Paleo-Eskimos originating in Siberia crossed Beringia about 5000 years ago, mixing with indigenous Americans from a previous wave of Siberian migrants, as well as a much later lineage called Neo-Eskimos, the team concludes. This tangled family tree underpins the ancestry of modern speakers of indigenous Na-Dene and Eskimo-Aleut languages.
Based on the DNA analysis, the group that gave rise to Kolyma1 identified by Willerslev’s team may be the ancestors, or very close relations, of the Paleo-Eskimos. “[They are] in the right spot to be ancestors, or related in some way, to the Paleo-Eskimos that expanded into North America around 5000 years ago,” Potter says. “It fits together really nicely.”