A new study has found that Native Americans in the Amazon bear an unexpected genetic connection to indigenous people of Australasia. The results suggest a previously unknown wave of migration to the Americas thousands of years ago:
“It’s incredibly surprising,” said David Reich, Harvard Medical School professor of genetics and senior author of the study. “There’s a strong working model in archaeology and genetics, of which I have been a proponent, that most Native Americans today extend from a single pulse of expansion south of the ice sheets—and that’s wrong. We missed something very important in the original data.”
Previous research had shown that Native Americans from the Arctic to the southern tip of South America can trace their ancestry to a single “founding population” called the First Americans, who came across the Bering land bridge about 15,000 years ago. In 2012, Reich and colleagues enriched this history by showing that certain indigenous groups in northern Canada inherited DNA from at least two subsequent waves of migration.
The new study, published July 21 in Nature, indicates that there’s more to the story.
Researcher Pontus Skoglund was studying genetic data gathered as part of a previous study when he noticed the link between a couple of Native American groups in Brazil and indigenous groups in Australasia. Reich admitted that it was “an unexpected and somewhat confusing result…we spent a really long time trying to make this result go away and it just got stronger.”
After looking into this link further, they found that the Tupí-speaking Suruí and Karitiana, and the Ge-speaking Xavante of the Amazon shared a common ancestor – no longer in existence – more closely related to indigenous Australasians than any other present-day population, though no traces of this ancestor’s genetic lineage were found in other Native American groups in South, Central or North America.
While the migration route of this ancestral group remains a mystery, the study proposes that ‘Population Y’ came down from the ice sheets along with the First Americans, forming the two founding populations of the Americas.