The Ancient Ancestors of Modern Europeans: Three Groups, Not Two, Create Today's Genetics

First Posted: Sep 18, 2014 08:18 AM EDT
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About 7,500 years ago in Europe, two ancient populations of people mixed, forming the genetic combination that still persists today. Now, researchers have found that there's more to the story; it turns out that a third population also contributed DNA to present-day Europeans as well as to the people who traveled across the Bering Strait into the Americas more than 15,000 years ago.

Before now, researchers believed that only two populations helped formed the modern genetics of today's Europeans. When agriculture swept in from the Near East, it brought early farmers into contact with hunger-gatherers. These two genetically distinct populations mixed and contributed to the DNA of modern Europeans. Yet it turns out that this isn't the full story.

"Prior to this paper, the models we had for European ancestry were two-ways mixtures," said David Reich, co-senior author of the new study, in a news release. "We show that there are three groups. This also explains the recently discovered genetic connection between Europeans and Native Americans. The same ancient North Eurasian group contributed to both of them."

In order to learn more about Europeans' genetic heritage, the researchers sequenced the DNA of more than 2,300 present-day people from around the world. They also examined the DNA from nine ancient humans from Sweden, Luxembourg and Germany. These bones came from hunter-gatherers who lived about 8,000 years ago before the arrival of farmer. There was also one farmer specimen from about 7,000 years ago. In the end, they found that Ancient North Eurasian DNA wasn't present in the hunter-gatherers or the early farmers. This suggested that the Ancient North Eurasians arrived in the area later.

"Nearly all Europeans have ancestry from all three ancestral groups," said Iosif Lazaridis, first author of the new paper, in a news release. "Differences between them are due to the relative proportions of ancestry. Northern Europeans have more hunter-gatherer ancestry-up to about 50 percent in Lithuanians-and Southern Europeans have more farmer ancestry."

While this latest research shows three ancient groups that contributed to today's European genetic profile, scientists believe there could be more. Yet studies can only go so far due to the limited number of ancient DNA samples. That said, the three-way models doesn't tell the whole story for certain regions of Europe, such as Mediterranean groups and Ashkenazi Jews, which have more Near East ancestry than anticipated.

Currently, the scientists hope to continue their research. More specifically, they want to figure out when Ancient North Eurasians arrived in Europe in the first place.

The findings are published in the journal Nature.

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