Modern Europeans descended from three groups of ancestors

There are at least three major, highly differentiated populations that have contributed substantial amounts of ancestry to almost everybody that has European ancestry today, a new study has found.
By comparing nine ancient genomes to those of modern humans, Howard Hughes Medical Institute (HHMI) scientists have shown that previously unrecognised groups contributed to the genetic mix now present in most modern-day Europeans.
"There are at least three major, highly differentiated populations that have contributed substantial amounts of ancestry to almost everybody that has European ancestry today," said David Reich, an HHMI investigator at Harvard Medical School.
Those include hunter-gatherers from western Europe, the early farmers who brought agriculture to Europe from the Near East, and a newly identified group of ancient north Eurasians who arrived in Europe sometime after the introduction of agriculture.

That means there were major movements of people into Europe later than previously thought, said the research team led by Reich and Johannes Krause at the University of Tubingen in Germany.
In the last five years, genetic evidence has demonstrated that migrants from the Near East brought agriculture with them to Europe when they arrived about 8,500 years ago.

But the genomes of present-day Europeans show signs that they come from more than just the indigenous hunter-gatherers and these early farmers.
Two years ago, Reich's group uncovered genetic evidence that most present-day Europeans are a mixture of groups related to southern Europeans, Near Easterners, and a third group most closely related to Native Americans.

"That was a crazy observation, but it's very strong statistically," Reich said.
"We argued that this is because of the contribution of an ancient north Eurasian population some of whose members contributed to the peopling of the Americas more than 15,000 years ago, and others of which later migrated to Europe," said Reich.
To clarify that early history, Reich's team, including more than 100 collaborators worldwide, collected genetic data from nine ancient skeletons and 203 present-day populations living all over the world.
Collaborators isolated human DNA and sequenced the complete genomes from the bones of a 7,000-year old skeleton found in Germany and eight skeletons of hunter-gatherers who lived in Luxembourg and Sweden about 8,000 years ago.

They compared those genomes to those of the 2,345 people in their contemporary populations.
"What we find is unambiguous evidence that people in Europe today have all three of these ancestries: early European farmers who brought agriculture to Europe, the indigenous hunter-gatherers who were in Europe prior to 8,000 years ago, and these ancient north Eurasians," Reich said.
The findings were published in the journal Nature.