A rare smidgen of ancient DNA has sharpened the picture of one of humanity’s greatest migrations. Some 15,000 to 25,000 years ago, people wandered from Asia to North America across a now-submerged land called Beringia, which once connected Siberia and Alaska. But exactly when these ancient settlers crossed and how many migrations occurred are hotly debated. Now, the oldest full genome to be sequenced from the Americas suggests that some settlers stayed in Beringia while another group headed south and formed the population from which all living Native Americans descend.
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The genome comes from an 11,500-year-old infant found in 2013 at the site of Upward Sun River in central Alaska’s Tanana River Basin, a part of Beringia that’s still above sea level. The infant, one of two from the site, belonged to a population that likely numbered in the low thousands, who hunted Beringia’s abundant herds and gathered plants.
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Why did one group linger and thrive in Beringia while another took off to explore the Americas? A search for fresh resources could have spurred the migrants, [geneticist Eske] Willerslev says, but so could sheer curiosity. “There were people who were happy with what they had, and there were others who looked out at the great ice caps and wanted to see what was on the other side,” he says.
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