Chief Almir of the Surui Tribe of Brazil. Researchers say his people share ancestry with indigenous groups in Australia, New Guinea and the Andaman Islands. Photo by Andrea Ribeiro / Google

Indigenous peoples in South America, Australia and New Guinea share common ancestry, according to a study published today in the journal Nature.

Researchers looked at the DNA of 30 Native American populations in Central and South America. They found that some groups -- mainly two tribes in the Amazons of Brazil -- share ancestry with indigenous groups in Australia, New Guinea and the Andaman Islands off the coast of India.

But the shared genetic material was not found in other present-day Native American populations, according to the study. And it wasn't found in East Asian groups that have been connected to some present-day Native Americans.

The discrepancy led some researchers to conclude that the Americas were populated by another set of ancestors not previously known to scientists. Many of them believe Native Americans descend from a similar, or even single, group of people.

Researchers mapped similarities in genes, mutations and random pieces of DNA of Central and South American tribes with other groups. Warmer colors indicate links between two tribes in Brazil and indigenous populations in Australia, New Guinea and the Andaman Islands. Image from Pontus Skoglund / Harvard Medical School / Nature

“It’s incredibly surprising,” David Reich, a Harvard Medical School professor of genetics and senior author of the study, said in a press release.

But a different group of researchers came to a different conclusion. They believe the Australasian genetic material showed up due to intermixing after the first Americans had already arrived.

The researchers in the first group are using the term Population Y -- from Ypykuéra, a word meaning ancestor in the language of the Surui and Karitiana peoples of Brazil -- to describe the ancestors with the unique DNA.

Get the Story:
‘Ghost population’ hints at long-lost migration to the Americas (Nature 7/21)
American History 201 (Harvard News 7/21)
Harvard study sheds new light on origin of Native American populations (The Boston Globe 7/21)
Where did the first Americans come from? New studies offer clues. (Christian Science Monitor 7/21)
Tracing Routes to America Through DNA, Both Ancient and New (The New York Times 7/21)
A DNA Search for the First Americans Links Amazon Groups to Indigenous Australians (Smithsonian 7/21)
Indigenous Australians have been found to be closely related to some tribes in the Amazon (Business Insider 7/21)

Get the Study:
Genetic evidence for two founding populations of the Americas (Nature July 2015)

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