South American Indians are partly descended from Pacific peoples, new study confirms – 04/01/2021 – Science

The idea that the South American Native Americans descended in part from groups related to the oldest people in Oceania has just gained weight thanks to genomic studies conducted by Brazilian researchers.

They found that the DNA of a multitude of indigenous peoples now found in a region from the Pacific coast to Mato Grosso do Sul across the Amazon is home to remnants of these distant kinships with people such as the Australian Aborigines and New Yorkers. Guinea.

The geographical distribution and variability of this so-called “Australasian genetic mark” suggests that it is very ancient and incorporated into the ancestors of the South American indigenous people long before they separated and formed the immense diversity of the ethnicities known to us today.

Details on the new findings can be found in an article in this week’s issue of the American science magazine “PNAS”. However, they still do not allow us to imagine a direct crossing of the ocean between places like Australia and our part of the continent, says Tábita Hünemeier, geneticist at USP and coordinator of the study.

“I think a route other than the northern hemisphere is very unlikely. Another point is that this Australian sign appears to be very old, while the settlement of the Pacific islands, which are closest to America, is very recent, ”she explains.

In works published in the past decade, Hünemeier and his colleagues such as Maria Cátira Bortolini from the UFRGS (Federal University of Rio Grande do Sul) had already identified the mysterious sign in Amazonian groups. The group named the people who carried this genetic material of the population Y (from “Ypikuéra”, a Tupi term meaning “ancestor”).

In summary, it can be said that the ancestors of the indigenous peoples would have emerged from at least two large population groups, probably between 20,000 and 15,000 years before the present. The largest contribution would have come from Siberian groups associated with ethnic groups still living in this region of Asia who crossed the so-called Beringia (land language that connected Alaska to Siberia in the north of the American continent). towards America.

However, this crossing, possibly on land, is accompanied by evidence of a faster route through the water that borders the Pacific coast and reaches the southern tip of the continent relatively quickly. After all, the oldest archaeological site in America is, for most scholars, a place called Monte Verde in southern Chile that is at least 15,000 years old.

The leap into the new study is precisely the discovery of the genomic signature of population Y in groups from the Pacific coast, such as the Chotunas (descendants of the ancient Mochica civilization in northern Peru), as well as its confirmation in a number of Brazilian ethnic groups such as the Caritianas and Surui from the Amazon, the Guaranis-Caiovás from Mato Grosso do Sul and the Xavantes from the east of Mato Grosso. The results came after a DNA analysis of nearly 400 people belonging to dozens of different South American races.

Another important detail: the Australasian genetic signal appears to be different in each population. This means that some indigenous peoples have a clearer genetic inheritance from the hypothetical population Y, while others rarely have this mark.

According to the USP researcher, this would explain why it is difficult to identify the Australasian signal in DNA extracted from ancient skeletons in America. With the extraction of genetic material from a few individuals from rare populations whose remains have reached us, detection would tend to be more difficult.

On the other hand, a trip along the coast during the Ice Age could also pose another mystery: the lack of the Australasian genetic signal in indigenous groups in North America. “A coastal route reduces the points of contact and the settlement of population groups. Entering the continent, on the other hand, would likely leave groups with this Y ancestry scattered, ”says Hünemeier.

For the geneticist, it is more likely that the groups that carried these genes also arrived in Beringia and mingled with the other ancestors of the first Americans who later spread along the Pacific route.

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