For nearly a century now, most scholars have agreed that the ancestors of Native Americans likely hailed from Siberia, trekking across the Bering Strait to Alaska via a long-gone land bridge. But certain aspects of the historic migrationâ€”including the settlersâ€™ specific region of origin, when exactly they left it and what drove them to seek new landsâ€”remain matters of debate to this day. A new DNA-based study published today in the American Journal of Human Genetics offers new insight into these questions.
Russiaâ€™s mountainous Altai Republic borders China, Mongolia and Kazakhstan. Inhabited since the Paleolithic, the region is barely larger than Maine but served as a vital gateway to Siberia and the cradle of widespread human lineages found across northern Eurasia. â€œItâ€™s a place where people have been coming and going for thousands and thousands of years,â€ said study co-author Theodore Schurr, an anthropology professor at the University of Pennsylania. According to one prevailing theory, it is also the area where ancestral Native Americans lived before peopling the New World.
Schurr and his team took blood samples from Altai residents and examined their mitochondrial DNA, which is maternally inherited, and Y-chromosome DNA, which passes from father to son. Their analysis showed genetic distinctions between northern and southern Altaians, who also differ from one another both linguistically and culturally. The team then looked for markers known to exist in Native American populations, including a mutation known as Q that is â€œseen ubiquitously across all the Americas,â€ Schurr said. â€œOur goal in working with these communities was to explore their own history in relation to each other but also to other Siberians, as well as the possible links of these groups to Native American population,â€ he explained.
The results revealed genetic ties linking Native Americans to all Altaians, with a significantly stronger relationship connecting the migrants to residents of southern Altai. The researchers also dated the last common genetic ancestor shared by Native Americans and southern Altaians to between 20,000 and 25,000 years ago, an indication of when the New Worldâ€™s earliest settlers left their homeland and headed for the Beringian landmass. â€œWe were able to better define the founding lineages of native Americans,â€ said Schurr, who hypothesized that the settlersâ€™ arrival in what is now Alaska took place some time later, between 15,000 and 20,000 years ago.
This timeline for ancestral Native Americansâ€™ departure adds to a growing body of evidence that humans colonized the Americas earlier than previously thought. …
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