Monday, June 22, 2015

The DNA of Europe

As a young reader, I loved Rosemary Sutcliff's historical novels for kids, which were mostly set in the British Isles between 3,000 B.C. and 1,000 A.D. From these stories, I got a sense of the ongoing waves of migration (or invasion) that happened there, leading to present-day Britain.

Often in the Bronze Age stories, there would be "hill people" or "little dark-haired people" who lived nearby the main characters. They were never explained, but clearly they had been there first.

News of some recent DNA research brought it all back to me. Scientists analyzed skeletons from a range of sites across Europe and found that three particular genetic groups dominate the DNA and can be dated:

[From about 45,000 years ago] until about 9,000 years ago, Europe was home to a genetically distinct population of hunter-gatherers, the researchers found. Then, 9,000 to 7,000 years ago, the genetic profiles of the inhabitants in some parts of Europe abruptly changed, acquiring DNA from Near Eastern populations.

Archaeologists have long known that farming practices spread into Europe at the time from Turkey. But the new evidence shows that it wasn’t just the ideas that spread — the farmers did, too.

The hunter-gatherers didn’t disappear, however. They managed to survive in pockets across Europe between the farming communities.

“It’s an amazing cultural process,” said David Reich, a geneticist at Harvard Medical School who led the university’s team. “You have groups which are as genetically distinct as Europeans and East Asians. And they’re living side by side for thousands of years.”

From 7,000 to 5,000 years ago, however, hunter-gatherer DNA began turning up in the genes of European farmers. “There’s a breakdown of these cultural barriers, and they mix,” Dr. Reich said.

About 4,500 years ago, the final piece of Europe’s genetic puzzle fell into place. A new infusion of DNA arrived — one that is still very common in living Europeans, especially in central and northern Europe.

The closest match to this new DNA, both teams of scientists found, comes from skeletons found in Yamnaya graves in western Russia and Ukraine.
So Sutcliff's hill people were those original hunger gatherers. The Celts were most likely descended from the Middle Eastern farmers. And her Bronze Age redheads were late-arriving Yamnaya descendents.

The new DNA evidence sheds some light on scholarly discussions about the spread of Indo-European languages as well. The DNA evidence shows the Yamnaya went east into Siberia as well as west in Europe:
For decades, linguists have debated how Indo-European got to Europe. Some favor the idea that the original farmers brought Indo-European into Europe from Turkey. Others think the language came from the Russian steppes thousands of years later.

The new genetic results won’t settle the debate, said Eske Willerslev, an evolutionary biologist at Copenhagen University who led the Danish team. But he did say the results were consistent with the idea that the Yamnaya brought Indo-European from the steppes to Europe.

The eastward expansion of Yamnaya, evident in the genetic findings, also supports the theory, Dr. Willerslev said. Linguists have long puzzled over an Indo-European language once spoken in western China called Tocharian. It is known only from 1,200-year-old manuscripts discovered in ancient desert towns. It is possible that Tocharian was a vestige of the eastern spread of the Yamnaya.

“We can just say that the expansion fits very well with the geographical spread of the Indo-European language,” said Dr. Willerslev.
Now if they can just fill me in on how much Neanderthal DNA is in these Yamnaya samples...

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