Research Reveals New Link In Australasian and South American Ancestry

A new DNA study  has confirmed that indigenous people living in multiple locations in South America are distantly related to the people of Australasia, an umbrella term that includes indigenous Australians and Melanesians (inhabitants of the islands of Oceania, which are located south of Southeast Asia).

This new genetic survey, which was led by geneticist Tábita Hünemeier and evolutionary biologist Marcos Araújo Castro e Silva from the University of São Paulo in Brazil, analyzed genetic data obtained from 383 indigenous people living in various areas of South America. After completing a comparative analysis, they discovered distinctive genetic traces that were shared by indigenous people in Australasia and three indigenous South American groups: the  Chotuna (from the Pacific coast region of Peru), the Guaraní Kaiowá (from west central Brazil), and the Xavánte (from central Brazil).

While this study is revealing in itself, what makes it especially noteworthy is its relationship to  a similar 2015 genetic study  carried out in the rainforests of Brazil. This research project found genetic links between the people of Australasia and two indigenous groups living in the Amazon, the  Karitiana and the Suruí . They named the set of genetic markers these groups all shared the ‘Y signal,’ referring to an indigenous Brazilian word ( ypikuéra) that means “ancestor.”

Amazon and Australian Aboriginals share common ancestors. Left: Amazon shaman (Veton PICQ, CC BY-SA 3.0). Right: Australian Aboriginal ( Steve Evans / CC BY-NC 2.0)

Amazon and Australian Aboriginals share common ancestors. Left: Amazon shaman (Veton PICQ,  CC BY-SA 3.0 ). Right: Australian Aboriginal (  Steve Evans / CC BY-NC 2.0 )

In fact, it is this same Y signal that has now been detected in the Chotuna, the Guaraní Kaiowá, and the Xavánte. So the new study confirms the 2015 study, but it also expands on it in important ways.

“Our results showed that the Australasian genetic signal, previously described as exclusive to  Amazonian groups, was also identified in the Pacific coastal population, pointing to a more widespread signal distribution within South America, and possibly implicating an ancient contact between Pacific and Amazonian dwellers,”  the researchers wrote  in an article appearing in the most recent edition of  PNAS.

The Story of Beringia and an Epic Journey to the Americas

Using software programs that allowed them to test different migratory scenarios, the Brazilian researchers concluded that the distinctive genetic markers that connect these disparate peoples were introduced to the  Americas sometime between 8,000 and 15,000 years ago. The ancestors who connect the indigenous people of Australasia with those of South America likely originated in what is now Southeast Asia, and it was from there that some sailed southward to  Australia and the islands of  Oceania while others migrated eastward to the Americas.

But the latter group wouldn’t have made their journey by sea, according to the Brazilian genetic research team. Instead, they would have participated in the epic, continuous, millennia-long migration that brought people from Eurasia and the surrounding areas to the Americas on foot. These travelers fanned out across North, South, and Central America, settling in all locations from coast to coast and building unique societies that were to remain undisturbed until the arrival of the  Europeans in the 15 th and 16 th centuries.

Lagoinha Beach, Ceará, Brazil (Luiza / Adobe Stock)

Lagoinha Beach, Ceará, Brazil ( Luiza / Adobe Stock)

This was possible because in the past, sea levels were much lower than they are now. In these distant times, Eurasia and the Americas were connected by a land bridge called  Beringia, which connected what is now Siberia with present-day Alaska. Between 20,000 and 15,000 years ago, migrants began to move from  Siberia across Beringia, populating that land but also moving beyond it in a series of migratory waves.

The migrants moved south and east, likely seeking more hospitable climes, and by approximately 14,800 years ago some had settled in the southernmost reaches of Chile, which marked the southern limit of their astonishing and history-altering travels. Most of these migrants (the descendants of the Native Americans) have been presumed to have come from Siberia originally, but some groups likely began their journeys from more distant locations (the ancestors linking indigenous Australasians and South Americans would have been one such group).

Migrations from Eurasia and Beringia to North, South, and Central America likely continued until approximately 11,000 years ago, when Beringia was submerged by rising sea levels associated with the end of the last  Ice Age .

The individuals who carried the Y signal in their genomes began their southward journey sometime before this, although it is uncertain just exactly how long it took them to reach the Pacific coast and the interior regions of Brazil after their migration began (hence the 7,000 year time frame for their possible arrival referenced by the Brazilian researchers in their study).

How Genetic Evidence Can Settle Historical Disputes (or Create New Ones)

When the results of the 2015 genetic study were announced, different interpretations for the results were offered. Some concluded that the ancestors of the Amazon rainforest peoples were a part of the ancient migrations, and had indeed traveled from Southeast Asia up through Beringia and ultimately down into the rainforests of South America. Other researchers believed the migrants must have come to South America at a much later time, sailing across the waters of the Pacific long after Beringia had disappeared beneath the sea.

The Brazilian researchers believe their findings will end this dispute. Given the currently identified patterns of genetic dispersal, which are much broader than previously suspected, they have concluded that the Beringia model must be correct. Migrants carrying the distinctive Y signal would have followed a Pacific coastal route through Central and South America several thousand years ago, and then split off into separate groups after reaching South America, with some heading east to the Amazon and Brazil’s central plateau.

“[The data] matches exactly what you’d predict if that were the case,”  confirmed Jennifer Raff , an anthropological geneticist from the University of Kansas who has closely analyzed the results of the Brazilian study.

Unfortunately, current knowledge about the dispersal of the Y signal genetic markers is extremely limited, making it impossible to definitively trace the migration patterns of the people who brought it to South America. More genetic studies will be required to find out for sure if the descendants of the carriers of this signal are confined to a few areas of this region, or are actually spread out over a much vaster area (possibly including Central and North America).

But two things can be asserted with a fair degree of confidence.

First, that the ranks of the sojourners who crossed Beringia before the end of the last Ice Age included individuals who carried the Y genetic signal to South America. And second, that other individuals who were related to these people carried this same signal to Australia and to the islands of Oceania. Whether their journeys to these two widely separated sections of the globes occurred simultaneously or at different times is another question that for now must remain unanswered.

Top image: Paracas National Reserve, Peru                    Source:  Erlantz / Adobe Stock

By Nathan Falde


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