History

European Hunter-Gatherers Interbred With Farmers From the Near East

The first farmers were not only well traveled, but also apparently well loved by the hunter-gatherers that they encountered across Europe.

Early populations from Europe and the Near East were not just farming, though. Extensive new DNA evidence reveals that they were making love, with hunter-gatherers frequently interbreeding with farmers.

The findings, published in the journal Nature, confirm earlier speculation about what happened when the two groups met and help to explain the ancestry of European people today. As it turns out, people of European heritage all have a little hunter-gatherer in their genetic makeup.

“It’s likely that most Europeans today retain a small proportion of ancestry from pre-farming groups who lived in the same region of the continent,” lead author Mark Lipson of Harvard Medical School’s department of genetics told Seeker.

For the new study, Lipson, senior author David Reich, and their colleagues analyzed the genomes of 180 ancient individuals who lived between 6,000 and 2,200 BC and were from what are now Hungary, Germany, and Spain.

The authors next built mathematical models that describe how ancient populations might have interacted as they moved from place to place.

The models show that for each of the three regions included in the study, the arrival of farmers prompted interbreeding with local hunter-gatherers. This trend was seen repeatedly over time, with the liaisons leaving distinct genetic signatures in each geographical region.

“I think, by nature, groups of people are more likely to mix and interact than not, regardless of cultural differences,” Lipson said. “We do find, though, that the admixture continued over an extended period, so it wasn’t all immediate.”

The liaisons appear to have been particularly consistent, however, in Hungary, the region in which the researchers had the most number of ancient DNA samples.

The data also suggest that farmers tended to travel a lot, while hunter-gatherers were more apt to stay fairly close to home.

“High population densities among farmers led them to expand to additional arable land,” Lipson said. “During this period, it seems likely that hunter-gatherers were not migrating such long distances, but our knowledge is not complete.”

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It would appear to be equally challenging to distinguish hunter-gatherers from farmers in the archaeological record and from DNA. Lipson indicated that the differences between the two are surprisingly not too difficult to tease apart.

He explained that artifacts and remains left behind by farmers and hunter-gatherers are distinctive to each group.

“On an individual level, differences in diet can also be detected by isotope ratios in bones and teeth,” he said. “And in places where farmers and hunter-gatherers are genetically differentiated, we can measure that by comparing their relationships to other populations.”

The DNA evidence further sheds light on the origins of the Neolithic farmers. Most appear to have been migrants from Anatolia, an area that today falls within Turkey. In geographic terms, this is the area bounded to the north by the Black Sea, to the east and south by the Southeastern Taurus Mountains and the Mediterranean Sea, and to the west by the Aegean Sea and the Sea of Marmara.

Anatolia was within the Fertile Crescent, also known as the cradle of civilization. This crescent-shaped region contains comparatively moist and fertile areas in what is otherwise an arid and semi-arid part of the present Middle East.

Going back even further in time than the Neolithic, prior research shows European hunter-gatherers had about the same amount of Neanderthal-derived ancestry as present-day East Asians, “which is slightly more than Neolithic Anatolians,” Lipson said.

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The precise reason for that difference, as for the reason behind the creation of many famous Neolithic European monoliths, still remains unknown.

In future, the researchers would like to apply their DNA analysis methods to other parts of the world. The results, as for this latest study, could show how different populations interbred — or not — after their fateful initial meetings.

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