Xavante woman from Brazil. Photo: Agência Brasil. Source: Harvard Medical School.
Native Americans who live in the Amazon have an unexpected genetic connection to indigenous people from Australia, what suggests a wave of migration to the Americas thousands of years ago, unknown to date, according to an American-Brazilian study, reports Tendencias21.
Previous researches had shown that native Americans, from the Artic to the southern end of South America, can locate their ancestry to just one “founder population”, named First Americans, who arrived across the land bridge of Bering 15,000 years ago.
In 2012, researchers from Harvard enriched this story when showing that certain indigenous groups from the North of Canada inherited the DNA of at least two later waves of migration. The new study, published in Nature, indicates that there are still more waves of migration.
When analysing data of 2012, authors noticed that there were a strange similarity between one or two native American groups from Brazil and indigenous groups from Australia, Nueva Guinea, and the Andaman Islands. Pontus Skoglund and his fellows from United States and from various Brazilian universities analysed the public genetic information of 21 American native populations from Central and South America.
Researches also gathered and analysed DNA of nine additional populations from Brazil to ensure that the observed link was not an artefact of the way the first set of genomes had been gathered. Afterwards, the group compared the genomes with the ones of the people of around 200 non-American populations.
The link persisted. The Suruí and the Karitiana, speakers of Tupí, and the Xavante, speakers of Ge from the Amazon rainforest, had a genetic ancestor more closely related to Australasian indigenous than to any other population today. This ancestor does not seem to have left a measurable mark in other groups of native Americans of South, Central, and North America.
Genetic markers of these ancestors do not fit in with any population that had contributed to the ancestry of native Americans. Neither the geographic pattern can be explained by the European, African, or Polynesian post-columbine mixture, say the authors, who believe that the ancestry is much older – maybe as older as the First Americans.
On the following millenniums, the group of ancestors had disappeared. “We had taken many samples in Asia Oriental, and nobody seems to this”, says Skoglund. “It is an unknown group that no longer exists.” The group has named the mysterious ancestors Y Population, for the Tupí word “Ypykuéra”, which means “ancestor”.
Researchers suggest that the Y Population and the First Americans descended from the ice-sheets to be transformed in the two founder populations from the Americas. “We do not know the order, the separation time, or the geographic patterns”, says Skoglund.
Researchers know that the DNA of the First Americans seems similar to the one of the native Americans of the present day. The Y Population is more mysterious. About the two percent of the ancestry of the current Amazonians come from this lineage of Australasia, which is not present in the same way elsewhere in America.
However, this will not clarify that part of their ancestry comes from the Y Population. If Y Population was hundred per cent from Australasia, this could mean that they contribute to the two percent of the DNA of the present Amazonians. But if the Y Population was mixed with other groups as the First Americans before arriving to the Americas, the amount of DNA that contributed to the present Amazonians could be much higher, up to the 85 per cent.
To answer this question, researchers should take samples of DNA of the rests of a person who belonged to the Y Population, but this DNA has not been obtained yet. The skeleton of the first native Americans could be a good place to look for this DNA, whose craniums are said to have characteristics of Australasia. Most of these skeletons were found in Brazil.
Previous researches had shown that native Americans, from the Artic to the southern end of South America, can locate their ancestry to just one “founder population”, named First Americans, who arrived across the land bridge of Bering 15,000 years ago.
In 2012, researchers from Harvard enriched this story when showing that certain indigenous groups from the North of Canada inherited the DNA of at least two later waves of migration. The new study, published in Nature, indicates that there are still more waves of migration.
When analysing data of 2012, authors noticed that there were a strange similarity between one or two native American groups from Brazil and indigenous groups from Australia, Nueva Guinea, and the Andaman Islands. Pontus Skoglund and his fellows from United States and from various Brazilian universities analysed the public genetic information of 21 American native populations from Central and South America.
Researches also gathered and analysed DNA of nine additional populations from Brazil to ensure that the observed link was not an artefact of the way the first set of genomes had been gathered. Afterwards, the group compared the genomes with the ones of the people of around 200 non-American populations.
The link persisted. The Suruí and the Karitiana, speakers of Tupí, and the Xavante, speakers of Ge from the Amazon rainforest, had a genetic ancestor more closely related to Australasian indigenous than to any other population today. This ancestor does not seem to have left a measurable mark in other groups of native Americans of South, Central, and North America.
Genetic markers of these ancestors do not fit in with any population that had contributed to the ancestry of native Americans. Neither the geographic pattern can be explained by the European, African, or Polynesian post-columbine mixture, say the authors, who believe that the ancestry is much older – maybe as older as the First Americans.
On the following millenniums, the group of ancestors had disappeared. “We had taken many samples in Asia Oriental, and nobody seems to this”, says Skoglund. “It is an unknown group that no longer exists.” The group has named the mysterious ancestors Y Population, for the Tupí word “Ypykuéra”, which means “ancestor”.
Researchers suggest that the Y Population and the First Americans descended from the ice-sheets to be transformed in the two founder populations from the Americas. “We do not know the order, the separation time, or the geographic patterns”, says Skoglund.
Researchers know that the DNA of the First Americans seems similar to the one of the native Americans of the present day. The Y Population is more mysterious. About the two percent of the ancestry of the current Amazonians come from this lineage of Australasia, which is not present in the same way elsewhere in America.
However, this will not clarify that part of their ancestry comes from the Y Population. If Y Population was hundred per cent from Australasia, this could mean that they contribute to the two percent of the DNA of the present Amazonians. But if the Y Population was mixed with other groups as the First Americans before arriving to the Americas, the amount of DNA that contributed to the present Amazonians could be much higher, up to the 85 per cent.
To answer this question, researchers should take samples of DNA of the rests of a person who belonged to the Y Population, but this DNA has not been obtained yet. The skeleton of the first native Americans could be a good place to look for this DNA, whose craniums are said to have characteristics of Australasia. Most of these skeletons were found in Brazil.
English
