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Ancient DNA Reveal the Foundation Event of the Peopling of the Americas

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At a site known today as the Upward Sun River, near the Tanana River Valley in Central Alaska, Ben Potter of the University of Alaska Fairbanks unearthed the cremated remains of a 3-year-old child in 2010. About a meter deep, and three years later, two infants were found buried in a circular pit filled with grave goods underneath the other child. At six weeks old, one was laid to rest near the remains of a stillborn baby, perhaps a first cousin. The grave included blades and hunting tools. Xaasaa Cheege Ts’eniin or Upward Sun River Mouth Child was the name given to the first child by the local Healy Lake Tribe. This individual failed to yield ancient DNA.

The excavation of one of the ancient infants buried at the Upward River Sun site in Alaska. Photo by Ben Potter

The excavation of one of the ancient infants buried at the Upward River Sun site in Alaska. Photo by Ben Potter

The other two infants were named one Xach’itee’aanenh t’eede gaay or sunrise child-girl, the six week old, and the other Yełkaanenh t’eede gaay or dawn twilight child-girl, the likely stillborn cousin. Both covered in red ochre and buried together in a pit burial with four decorated antler rods, two lithic dart points and bifaces. With their descendant’s permission we are now learning the early events in the peopling of the Americas. We already thought we knew that ancient humans from Siberia crossed Bering land bridge into Alaska, descendants who crossed a land connection between Asia and North America sometime during the Last Glacial Maximum (26,500 to 19,000 years ago). We didn’t have clarity on exacting how and where these migrations occurred.

A new paper in NatureTerminal Pleistocene Alaskan genome reveals first founding population of Native Americans, studies the genetics of one of the infants from the Upward Sun River Site. Radiocarbon dating of the individuals reveal that they were roughly 11,500 years old.  Eske Willerslev at the University of Copenhagen has sequenced the complete genome of the 6-week-old infant, sunrise girl-child, the only one of the three who yielded enough ancient DNA. Her DNA was related to the founding population of Native Americans that originated in Siberia. It was added to computer simulations of the timeline of the peopling of North America.

The nuclear genome of sunrise girl child confirm that she belonged to a group which persisted Beringia after Native Americans began their migration southward into the Americas. Nearly half of the girl’s DNA is related to the ancient north Eurasians who lived in what is now Siberia. The rest of her is a roughly an even mix of DNA now carried by the northern and southern Native Americans. Because her genome is equally related, it tells us that her group likely founded a migration event. It goes something like this, around 36,000 years ago in northeast Asia, groups related to modern Native Americans began splitting off from ancestral Asians. But they didn’t completely split. Gene flow continued with other Asian populations. At around  25,000 years ago, the swapping of genes stopped and they were cut off from the rest of Asia, possibly during a migration event.

Around 20,000 years ago, the Ancient Beringians subgroup branched off from the ancestors of modern Native Americans. This single founding population migrated into Beringia and remained for a period termed the Standstill, Pause or Incubation, lingering here long enough for at least three lineages to branch apart. One group, as represented by our sunrise girl child of the ancient Beringians that remained icy north, while two populations then migrated separately into the New World, sometime around 17,000 to 14,600 years ago… Showing the peopling of the Americas can be traced back to one source population, via a single, founding migration event.

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