WEDNESDAY, Sept. 17, 2014 (HealthDay News) -- Present-day Europeans are the descendants of at least three groups of ancient humans, according to a new study.

Previous research suggested that Europeans descended from indigenous hunter-gatherers and early European farmers. But, a new genetic analysis involving ancient bone samples revealed they are also the descendants of Ancient North Eurasians. Nearly all present-day Europeans have genetic material from this third ancestral group, researchers from Harvard Medical School said.

In conducting its investigation into Europeans' heritage, the team of researchers collected and sequenced the DNA of more than 2,300 people currently living around the world. They also examined DNA from nine ancient humans from Germany, Luxembourg and Sweden.

The ancient samples were taken from the bones of eight hunter-gatherers who lived about 8,000 years ago, and one farmer who lived about 7,000 years ago.

"Ancient DNA has emerged as a powerful technology that makes it possible to go back in time to understand how people in the past relate to people today," study co-senior author, David Reich, professor of genetics at Harvard Medical School, said in a university news release.

About 7,500 years ago in Europe, agriculture from the Near East brought early farmers into contact with hunter-gatherers who had been living in Europe for tens of thousands of years. Nearly all Europeans are the result of the mixing of these two ancient populations.

"There was a sharp genetic transition between the hunter-gatherers and the farmers, reflecting a major movement of new people into Europe from the Near East," noted Reich.

The study's authors found, however, Ancient North Eurasians also contributed DNA to present-day Europeans. Ancient North Eurasians also likely contributed DNA to people who crossed the Bering Strait into the Americas more than 15,000 years ago, according to the researchers.

"Nearly all Europeans have ancestry from all three ancestral groups," explained the study's first author, 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 percent in Lithuanians -- and Southern Europeans have more farmer ancestry," Lazaridis said in the news release.

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Europeans Are Descendants of at Least 3 Ancient Human Groups: Study