Genetic analysis has revealed that present-day Europeans descended from at least three and not two groups of ancient humans.
About 7,500 years ago, agriculture was sweeping in from the Near East bringing early farmers into contact with hunter-gatherers who had already been living in Europe for tens of thousands of years.
Genetic and archaeological research in the last 10 years has revealed that almost all present-day Europeans descend from the mixing of these two ancient populations.
But it turns out that’s not the full story.
Researchers at Harvard Medical School and the University of Tübingen in Germany have now documented a genetic contribution from a third ancestor: Ancient North Eurasians.
This group appears to have contributed DNA to present-day Europeans as well as to the people who travelled across the Bering Strait into the Americas more than 15,000 years ago.
“Prior to this paper, the models we had for European ancestry were two-way mixtures. We show that there are three groups,” says David Reich, professor of genetics at Harvard.
“This also explains the recently discovered genetic connection between Europeans and Native Americans. The same Ancient North Eurasian group contributed to both of them.”
The research team also discovered that ancient Near Eastern farmers and their European descendants can trace much of their ancestry to a previously unknown, even older lineage called the Basal Eurasians.
The study is published in the journal Nature.
As part of the study, the scientists collected and sequenced the DNA of more than 2,300 present-day people from around the world and of nine ancient humans from Sweden, Luxembourg and Germany.
The ancient bones came from eight hunter-gatherers who lived about 8,000 years ago, before the arrival of farming, and one farmer from about 7,000 years ago.
The researchers also incorporated into their study genetic sequences previously gathered from ancient humans of the same time period, including early farmers such as Ötzi “the Iceman.”
Ancient North Eurasian DNA wasn’t found in either the hunter-gatherers or the early farmers, suggesting the Ancient North Eurasians arrived in the area later.
“Nearly all Europeans have ancestry from all three ancestral groups,” said Iosif Lazaridis, a research fellow in genetics in Reich’s lab.
“Differences between them are due to the relative proportions of ancestry. Northern Europeans have more hunter-gatherer ancestry, up to about 50% in Lithuanians, and Southern Europeans have more farmer ancestry.”
The team was able to go only so far in its analysis because of the limited number of ancient DNA samples.
Reich thinks there could easily be more than three ancient groups who contributed to today’s European genetic profile.
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