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Researchers found Australasian ancestry in indigenous groups living across South America, including those from the Mochica civilization of Peru.
Luis Rosendo / Heritage Images / Getty Images
By Michael Price
In 2015, scientists discovered something surprising: that some indigenous peoples of the Brazilian Amazon were distant – but distinctly – linked to indigenous Australians and Melanesians. The genetic signal of Australasian ancestry in such a distant population has prompted researchers to seek answers. New study finds this genetic signal is more prevalent across South America than one might think, and suggests people who first carried these genes in the New World got it from a population ancestral Siberian.
The discovery also sheds light on the migratory routes of these people to South America. “It’s a very nice job,” says Jennifer Raff, an anthropological geneticist at the University of Kansas, Lawrence, who was not involved in the study. This shows that the 2015 discovery “was not just an artefact. It really is a widely spread genetic signal. “
Anthropologists believe that groups of hardy hunter-gatherers left Siberia and entered the now submerged land of Beringia, which then connected Eurasia and Alaska, when the sea level was much lower than today, maybe 20,000 years ago. Then, about 15,000 years ago, some left Beringia and dispersed to North and South America. These early migrants had a good time: 14,800 years ago at the latest, radiocarbon dates suggest they were setting up a camp at Monte Verde in southern Chile.
DNA studies from 2015 revealed Australasian ancestry in two indigenous Amazonian groups, the Karitiana and Suruí, based on the DNA of more than 200 living and ancient people. Many carried a distinctive set of genetic mutations, called a “Y signal” after the Brazilian word Tupi meaning “ancestor”. ypikuera. Some scientists have speculated that the Y signal was already present in some of the early South American migrants. Others have suggested that a subsequent migration of people related to today’s Australasians may have introduced the Y signal to people already living in the Amazon.
The new study, led by geneticist Tábita Hünemeier of the University of São Paulo, São Paulo, examined genetic data from 383 modern people from South America, including dozens of newly genotyped individuals living in the Amazon. Brazilian and the central plateau. The researchers worked closely with indigenous peoples, and Hünemeier says they are collaborating with historians, anthropologists and geneticists “to ensure that the results are transferred in the best way to indigenous communities.”
For the first time, scientists have identified the Y signal in groups living outside the Amazon – in the Xavánte, who live on the Brazilian plateau in the center of the country, and in the Chotuna of Peru, who descend from civilization Mochica which occupied the coast of this country from around 100 CE to 800 CE
Next, the researchers used software to test different scenarios that could have led to the current dispersal of DNA. The most suitable scenario concerns some of the oldest, and even the oldest: South American migrants carrying the Y signal with them, researchers in the Proceedings of the National Academy of Sciences. These migrants likely followed a coastal route, says Hünemeier, and then separated between the central plateau and the Amazon some time between 15,000 and 8,000 years ago. “[The data] is exactly what you would predict if it were, ”confirms Raff.
David Meltzer, archaeologist at Southern Methodist University and co-author of the 2015 study identifying the Y signal, says this explanation makes sense. Still, he adds, finding Australasian ancestry in ancient coastal remains would boost his confidence in the authors’ conclusions.
Pontus Skoglund, a population geneticist at the Francis Crick Institute and co-author of one of the 2015 studies with Hünemeier, says he’s happy to see South American scientists build on previous work. “I am delighted that local research groups in Brazil are taking this into account. They are doing exactly the right thing. “
An unanswered question is why the Y signal did not appear in any indigenous group in North or Central America. One possibility, suggests Hünemeier, is that migrants with Y signals simply clung to the coast and made their way to South America without leaving a genetic inheritance in the north. It is also possible that groups of Y ancestry lived in North and Central America, but died out in the aftermath of European colonization. “The population Y signal is a puzzle,” says Meltzer, “but it’s an interesting piece to add to it.”
* Correction, March 29, 3:40 p.m .: This article originally listed the incorrect affiliation for Tábita Hünemeier.
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