Native Americans Spent 10,000 Years on Bering Land Bridge

In a new finding, researchers suggest that early North American migrants from northeast Asia spent thousands of years taking long-term refuge on the Bering Land Bridge, which is now submerged under the Bering Sea.

Based on ancient genetic and environmental evidence, a new study led by researchers at the University of Utah revealed that the early Native Americans spent nearly 10,000 years seeking refuge in the shrubby lowlands on a broad land bridge that connected Siberia and Alaska in the past. This occurred during the ice age 'last glacial maximum'

According to a team of anthropologists, the first Native Americans migrated from Siberia some 25,000 years ago over the Bering Land Bridge. No archaeological traces of these migrants were found until 10,000 years ago.

In this study, the scientists explained that the early Native Americans were initially isolated on the land bridge. However, when this broad land bridge vanished due to rising sea levels, evidence of the Beringian culture was washed away, source NBC News.

Anthropologist Dennis O'Rourke along with his two colleagues plan to bring together genetic and paleo-environmental clues to prove the existence of humans on Beringia despite any archaeological evidence.

The theory currently known as the 'Beringia Standstill' was initially proposed in the year 1997 by two Latin American geneticists. The theory was later improved in 2007 by researchers at the University of Tartu in Estonia after sampling mDNA from nearly 600 Native Americans. During this analysis, they recognized that their direct ancestors were a group of Siberians that were isolated on Beringia. They moved out of Siberia 25,000 years ago, though archaeological evidence dates back 15,000 years ago.

 There has been a growing debate on when early Native Americans migrated to the New World

"A number of supporting pieces have fallen in place during the last decade, including new evidence that central Beringia supported a shrub tundra region with some trees during the last glacial maximum and was characterized by surprisingly mild temperatures, given the high latitude," CU-Boulder researcher John Hoffecker, lead author of a short paper said in the news release.

The paper by Hoffecker, Dennis O'Rourke and co-authro Scott Elias of Royal Holloway offers new clues that support the presence of Beringia culture now lost under the sea.

They highlighted a past study on ancient environment where scientists drilled sediment cores from the Bering Sea and found that the sediments contained traces of fossilized pollen, plants and insects. This clearly indicated that the land bridge, which was about 600 miles wide then, was not barren but was occupied by migrants.

"We're putting it together with the archaeology and genetics that speak to American origins and saying, look, there was an environment with trees and shrubs that was very different than the open, grassy steppe. It was an area where people could have had resources, lived and persisted through the last glacial maximum in Beringia," O'Rourke said in a statement. "That may have been critical for the people to subsist because they would have had wood for construction and for fires. Otherwise, they would have had to use bone, which is difficult to burn."

Analysis of beetles from the sediment cores offer clues on the temperature during the last glacial maximum. It is estimated that temperatures were mild and slightly cooler than the current temperature of the region. When the land bridge existed, the climate was a bit wetter and the data reveals the presence of woody shrubs on the land bridge that the researchers assume were used for making fire.

A genetic study done in 2007 showed mutation in the mDNA that was transfered from mother to offspring, adding weight to evidence that Native Americans came before 25,000 years but didn't enter America until 15,000 years ago.

"The genetic record has been very clear for several years that the Native American genome must have arisen in an isolated population at least by 25,000 years ago, and the bulk of the migrants to the Americas really didn't arrive south of the ice sheets until nearly 15,000 years ago," O'Rourke said. "The paleoecological data, which I think most geneticists have not been familiar with, indicate that Beringia was not a uniform environment, and there was a shrub tundra region, or refugium, that likely provided habitats conducive to continuous human habitation."

The team believes that studies done in the future on Beringia, the lowlands in Western Alaska and eastern Siberia that is still above water, may offer clues on the ancient habitat of Beringia residents.