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Europe is one big family

Continent shares common ancestry about 30 generations ago

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The branches of Europe’s family tree converge remarkably recently in the continent’s history — around the time of the Norman conquest and the Vikings’ transatlantic voyages.

Virtually every person living in Europe today shares a common set of ancestors that lived about 1,000 years ago, Peter Ralph and Graham Coop of the University of California, Davis report May 7 in PLOS Biology.

“What’s really surprising is just how closely related Europeans — and likely all people in the world — are,” Coop says.

In the past, mathematical analyses have concluded that everyone on the globe shares not just a single ancestor, but a complete set of ancestors who lived about 3,000 years ago. In other words, all of the people living then who have modern descendants are ancestors of everyone living today.

Ralph and Coop set out to test this idea using genetic data. Previously, researchers relied on specific bits of DNA passed exclusively from a person’s mother or father to sketch broad pictures of humans’ ancient history. But by looking through all of the DNA inherited from both parents, Coop’s team was able to fill in some of the more recent details.

Ralph and Coop scanned a dataset containing the genomes of 2,257 Europeans, looking for shared signatures sprinkled throughout people’s DNA. Because long shared chunks tend to come from recent ancestors and short chunks from ancient ones, the researchers could estimate how long ago two people shared a relative.

Then the researchers calculated how many ancestors various pairs of Europeans shared to determine how closely they were related. The researchers’ genetic calculations supported the earlier theoretical work: The DNA data show that everyone living in Europe 1,000 years ago who left any descendants is an ancestor of every European living today.

Next, Ralph and Coop matched up genetic details about local populations with historical data.

Eastern Europeans tended to be slightly more related to each other than to people from other regions, Ralph and Coop found. These close family ties support the historical and linguistic evidence that Eastern Europeans largely descend from Huns and Slavs who migrated from the East during the fourth through the ninth centuries.

Unlike Eastern Europeans, Italians shared fewer ancestors with each other and with other Europeans. Their lack of common ancient relatives meshes with the idea that Italy had a large and stable population that was fed by a diverse assortment of people and not overwhelmed by any single group of migrants.

The work is “a real advance,” says population geneticist John Novembre of the University of Chicago. “We’ve never had the resolution to see these kinds of historical events before.”

Because population genetic data can tease apart the details of people’s ancestry, Coop says the information can help flesh out human history. Next, he’d like to analyze genetic data from people all around the world.

“We’re really excited to think about doing this for larger collections of human populations,” Coop says.

The finding that Europeans are a tight-knit bunch is bound to be true in other groups of people too, he says. Studying larger groups can also help researchers learn about historical events across the globe over the past few thousand years, he says.

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