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Ice Age Babies Buried in Alaska Reveals Early Genetic Diversity in North America

The infants’ DNA shows that humans may have stayed near the Bering Strait for thousands of years before moving farther south

Archeologists working at the Upward Sun River site in Alaska, where they found the 11,500-year-old remains of two infants (Ben Potter, University of Alaska Fairbanks)
smithsonian.com

For the people that buried them 11,500 years ago, the death of two infants at an Alaskan fishing campsite was surely tragic. But for scientists who discovered them many centuries later, they were an exciting find. The DNA of these two babies tells a previously unknown story of migration.

The 6-to-12-week old baby and a stillborn or preterm 30-week-old fetus represent two different genetic lineages that are rare in modern Native American populations. The findings reveal that the people living in Ice Age Alaska were more diverse than previously thought, reports Yereth Rosen for Arctic Newswire

Most scientists think that the first people to enter the Americas crossed the land bridge over the Bering Strait between 23,000 and 30,000 years ago. But the story beyond these basic details—like exactly how many groups crossed and how quickly they dispersed through the continents—looks to be a less than straightforward tale. During recent decades, scientists have learned that some groups that once lived in the subarctic vanished and others migrated farther south, but the timeline is still fuzzy.

The findings, published this week in Proceedings of the National Academy of Sciences, add weight to the idea that people settled in the area around the Bering Strait for as long as 10,000 years before moving farther south. This idea is called the Beringian Standstill hypothesis, named for the region, Beringia, where the ancient migration would have paused for thousands of years.

Both babies, along with the cremated remains of a three-year-old child, evidence of several dwellings, and a large number of artifacts, come from a location now called the Upland Sun River site, east of Fairbanks, Alaska near the Tanana river.  While the researchers don’t know how they died, the babies were buried in a ceremonial fashion, placed on red ocher and surrounded by hunting darts fashioned from antlers, reports Carl Zimmer for The New York Times.

The research team analyzed the infants’ mitochondrial DNA, genetic material from the structures sometimes called cell powerhouses, because they produce energy. This DNA is inherited only from a person’s mother, so provides a way to trace maternal lineages. 

Surprisingly, the infants did not share a mother but rather originated from two separate genetic lineages. At other ancient sites, human remains tend to be from single families, according to a press release. The fact that both lineages lived so far north so long ago bolsters the standstill model.

"You don't see any of these lineages that are distinctly Native American in Asia, even Siberia, so there had to be a period of isolation for these distinctive Native American lineages to have evolved away from their Asian ancestors," Dennis O’Rourke, author on the paper, says in the press release.

The babies have some of the oldest mitochondrial DNA ever analyzed in North America. Yet an older site would provide more conclusive support for the standstill model, according to Ripan Malhi, who was part of the group that originally proposed the model in 2007.

“It’s valuable information, but it’s a little bit late to be extremely informative to let us know if the Beringian Standstill hypothesis holds,” he tells Zimmer.

But finding that older site may prove to be tricky. "There are archaeologists up there looking for such sites," he says. "But I think it’s probably unlikely, largely because a lot of Beringia is now under water."

Without that confirmation, the babies and the encampment where their families lived still provide a valuable look into an ancient time. The artifacts at the site indicate the people there engaged in some of the earliest salmon fishing found in Alaska. And the genetic material adds valuable nuance to the complicated picture of early Native American history.

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