By Tia Ghose
The Americas may have been initially settled in two different migrations, a new method for tracing human ancestry reveals. The analysis also suggests populations in the Orkney Islands, a string of islands north of Scotland, share substantial common ancestry with northern Siberian populations.
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The new work by researchers in the United Kingdom and Ireland supports most previous findings, including the “Out of Africa” hypothesis that all humans share common ancestors who first spread from Africa about 50,000 years ago. “The conclusions aren’t all that novel, but the way that they’ve reached the conclusions is extremely novel,” says Donald Conrad, a population geneticist at the Wellcome Trust Sanger Institute in Cambridge, England, who was not involved in the study. “It’s a benchmark of what population genetic research can look like in the coming years.”
A few surprising results emerged from the analysis, published May 23 in PLoS Genetics. Native Americans from North and South America may have had different predecessors. While the North American Pima are genetically similar to Colombian populations, the Pima also had connections to present-day Mongolians. The genetic link to Mongolians suggests that two waves of migrants crossed the Bering Strait into North America. The first group probably made it all the way to South America, while a second group mixed with the first but never made it past North America, says Garrett Hellenthal, a statistician at OxfordUniversity in England who was involved in the study.