How did it spread? Were hunter-gatherers converted to the efficiencies of agriculture? Or did farmers from the south spread north, bringing their agriculture with them?
A new study suggests that farming spread because farmers moved. The movement was slow, taking five to six thousand years to reach Scandinavia. Early in the process, farmers of southern ancestry lived side by side with their more northerly human cousins, who still lived by hunting and gathering. Eventually, after a thousand years or so, farmers interbred with hunter-gatherers and farming became the dominant way of life.
The new study, which appears in the April 27 issue of Science, is based on an analysis of four skeletons, all found in Sweden and dating from about 5,000 years ago. Three were hunter-gatherers and one was a farmer. All of them lived their entire lives close to where they were buried, the hunter-gatherers in a flat grave and the farmer a stone megalith like the one pictured below.
Caption: Several hundred megalith tombs are known from the Falbygden area, including Gökhem and Valle parishes in Östergötland,Sweden.Credit: Göran Burenhult
"We know that the hunter-gatherer remains were buried in flat-bed grave sites, in stark contrast to the megalithic sites that the farmers built," said Mattias Jakobsson, a senior author from Uppsala University. "The farmer we analyzed was buried under such a megalith, and that's just one difference that helps distinguish the two cultures," Jakobsson said in a press release issued by the journal.
What is most significant in this study comes from an analysis of the human DNA extracted from the four skeletons. By studying their DNA, researchers found that the farmer belonged to a community with ancestral roots in the eastern Mediterranean, most closely resembling today's Greeks and Cypriots. The hunter-gatherers, on the other hand, were more like today’s northern Europeans, most closely resembling today's Finns. "What is interesting and surprising is that Stone Age farmers and hunter-gatherers from the same time had entirely different genetic backgrounds and lived side by side for more than a thousand years, to finally interbreed," Jakobsson said.
Caption: The skeleton belongs to a young female in her 20s, and can be dated to around 4,700 years ago. Credit: Göran Burenhult
"The results suggest that agriculture spread across Europe in concert with a migration of people," added Pontus Skoglund, also of Uppsala University. "If farming had spread solely as a cultural process, we would not expect to see a farmer in the north with such genetic affinity to southern populations."
The article, entitled "Origins and Genetic Legacy of Neolithic Farmers and Hunter-Gatherers in Europe," appears in the April 27 issue of Science, published by the American Association for the Advancement of Science.