Genetic evidence for two founding populations of the Americas

Genetic studies have consistently indicated a single common origin of Native American groups from Central and South America (1-4). However, some morphological studies have suggested a more complex picture, whereby the northeast Asian affinities of present-day Native Americans contrast with a distinctive morphology seen in some of the earliest American skeletons, which share traits with present-day Australasians (indigenous groups in Australia, Melanesia, and island Southeast Asia) (5-8). Here we analyse genome-wide data to show that some Amazonian Native Americans descend partly from a Native American founding population that carried ancestry more closely related to indigenous Australians, New Guineans and Andaman Islanders than to any present-day Eurasians or Native Americans. This signature is not present to the same extent, or at all, in present-day Northern and Central Americans or in a ~12,600 year-old Clovis-associated genome, suggesting a more diverse set of founding populations of the Americas than previously accepted.
All Native American groups studied to date can trace all or much of their ancestry to a single ancestral population that probably migrated across the Bering land bridge from Asia [...]