They arrived in the Stone Age and transformed Europe's population. A genetic study reveals that many Europeans are descended from people who moved out of the Iberian peninsula – present-day Spain and Portugal – in a massive wave of migration that began around 6000 years ago.
Modern hunter-gatherers arrived in Europe around 45,000 years ago, followed much later by the first farmers, who arrived from the Middle East 10,000 years ago. Over the next few millennia, society changed rapidly as hunter-gatherers declined, replaced by farmers who developed powerful chiefdoms and technologies for working with metal.
But there was at least one more major migration after this initial wave, says Wolfgang Haak of the University of Adelaide in Australia.
Using samples of DNA from 37 skeletons found in a small area of eastern Germany, Haak and his colleagues studied how the population changed between 7500 and 3500 years ago. They were able to sequence the complete mitochondrial genome for each skeleton, and as the ages of the skeletons were already known, Haak could see how the genomes changed over time.
Haak found a sudden genetic shift in the late Stone Age. Between 6100 and 4200 years ago, genes that were common in the oldest samples were replaced by new genes. These replacement genes are found in over 40 per cent of modern western Europeans, whereas the older genes are virtually absent.
That suggests a new wave of migrants entered central Europe 6000 years ago. Haak found that the later skeletons were genetically similar to modern-day Iberians, and says this offers a hint as to where the second migration wave started. "We think it came from western Europe," he says.
That might be true, but we need much more genetic data to confirm the idea, says Mark Thomas of University College London. "This is a relatively small sample," he says, so the genetic shift could have arisen by pure chance.
Haak thinks the people coming from the west might be linked to the Beaker culture, which created distinctive bell-shaped pots. Beaker culture began in Iberia and spread over much of western Europe, beginning around 4800 years ago. "Over the course of 300 years, we see the spread of the culture," says Haak. He thinks it might have been carried out of Iberia by migrants heading east into central Europe.
Thomas agrees that there is archaeological evidence for a second migration, but he says genetics should be used to rigorously test that hypothesis. "There isn't any testing here."
Journal reference: Nature Communications, doi.org/mbk
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