Two ice-age infants discovered in Interior Alaska left a genetic record that suggests ancient culture in this part of the world was more diverse and complex than previously understood, new research shows.
The infants -- one who died at about 6 weeks of age and one who died preterm at over 30 weeks of gestation -- were buried together and discovered in 2013 at a location east of Fairbanks near the Tanana River. The infants were buried with objects like decorated dart points and antler rods below what was determined to be an ancient hearth. Above the hearth were the cremated remains of a 3-year-old, found in 2010.
All of the findings date to about 11,500 years ago.
They are now the oldest human remains found in northern North America; the location is known as the Upward Sun River site.
Now DNA analysis reveals that the infants had different mothers and descended from lineages that are "rare to absent" in modern northern populations, said the study, which was published Monday in the Proceedings of the National Academies of Science.
That the infants had separate mothers is an unusual result for such old human remains, said study co-author Ben Potter, a University of Alaska Fairbanks archaeologist who has worked at the site for several years and was part of the team that made the original discovery. At other ancient sites, human remains buried together tend to be from single families, he said.
This site "gives us a better sense of the population, the genetic diversity at the time," Potter said.
Additionally, the infants' mitochondrial DNA -- genetic information inherited only from mothers -- is valuable to modern science because so little has been recovered from ancient human remains. The Upward Sun River site is among only eight in North America dating back at least 8,000 years that have provided scientists with such DNA, a statement from UAF said.
That the infants died at about the same time and were buried together in apparent ceremonial fashion suggests that some hardship struck the entire group, Potter said. "This could be something that informs us more broadly about resource stress among the population," he said. He noted that the infants died in summer, normally a time of greater food abundance.
The genetic analysis adds to evidence supporting what is known as the "Beringian Standstill Hypothesis," the theory that descendants of the early Bering land bridge migrants lingered in the region for several thousand years instead of sweeping quickly down to more southern parts of North American and into South America.
The analysis also adds to other information coming out of the Upward Sun River site, an area originally explored in preparation for a proposed Alaska Railroad extension.
There were several dwellings at the site, and researchers discovered remains of animals that were likely game for the ancient inhabitants, as well as remains of fish. Scientists studying the site determined that the Upper Sun River people, considered Paleoindians, ate chum salmon, making the site the oldest in North America holding evidence of salmon harvests.
A report on that salmon evidence was published last month in the Proceedings of the National Academy of Sciences.
The burial discoveries also give hints about cultural practices and behavior at the time.
At the time the children were buried, the landscape was a series of vegetated sand dunes and different from the forest that exists now, Potter said. The climate was in transition, with species like poplar, willow and birch dominating the vegetation, he said. The tundra that existed there about 14,000 years earlier was gone, but the spruce-dominated boreal ecosystem had not yet arrived, he said.
Also at the time, the Upward Sun River site was a natural place for human habitation, he said. It was perched on the edge of ecosystems that provided different resources -- a floodplain where salmon could be caught and uplands where game animals roamed, he said.
It is possible that the Paleoindians had a "more nuanced, more sophisticated use of the landscape," and a varied diet similar to a more modern traditional subsistence diet for people of the region, Potter said.
Analysis of the Upward Sun River site continues. Work is underway to discover more genetic information, analyzing the entire genome, Potter said. There is also work underway to better understand the ancient diet, including isotope analysis, he said.
What is not underway is the Alaska Railroad extension that would have developed the area. The site is now protected for its archaeological value, Potter said, "so nothing will happen to it."