Thursday, March 24, 2016

After the first Americans migrated from Asia they spent up to 10,000 years in Beringia before moving south into the Americas

About 11,500 years ago, two infants were laid to rest side by side in a shallow grave 80 kilometers southeast of what is now Fairbanks, Alaska. The area was once part of Beringia, a strip of ice-free land connected to Asia during the last ice age. Researchers found the remains in 2013, and have now sequenced the complete mitochondrial genomes of the two children. The results revealed that the infants had different mothers and that their genetic signatures are found today throughout North and South America.

Anthropologists have long suspected that the Americas were populated by nomadic people from Asia who migrated over the Bering land bridge during the last ice age, when sea levels were much lower. Glacial evidence suggests that this land bridge was open between 28,000 and 18,000 years ago. However, the oldest evidence of people in the Americas dates to about 15,000 years ago, leaving researchers to wonder what took these nomads so long to move south from Beringia after crossing the land bridge.

The newly published mitochondrial DNA sequences — the oldest sequences recovered to date this far north — lend support to an idea called the Beringian standstill hypothesis. The hypothesis suggests that after the first Americans migrated across the Bering land bridge from Asia, they spent up to 10,000 years in Beringia before moving south into the Americas, possibly because ice blocked the route.

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