DNA shows how Stone Age farmers mixed with hunters

A DNA analysis of four Stone Age humans in Europe published Thursday reveals how farmers likely migrated northward from the Mediterranean and eventually bred with hunter-gathers. The research, by a Swedish-Danish team and published in the US journal Science, sheds light on an oft-debated chapter of human history -- how did agriculture spread from the Middle East to Europe? Scientists believe that farming originated in the Middle East about 11,000 years ago, and had reached most of continental Europe by about 5,000 years ago. The latest findings suggest that farming techniques were introduced by southern populations who lived in the Mediterranean region and brought their know-how northward to hunter-gatherers. Researchers came to this conclusion after using advanced DNA analysis on four sets of Stone Age remains in Sweden -- one farmer and three hunter-gatherers -- dating back about 5,000 years. They could tell the difference in part by the way the remains had been buried -- the farmer in an elevated megalith stone tomb and the hunter-gatherers in flat bed grave sites. "We analyzed genetic data from two different cultures -- one of hunter-gatherers and one of farmers -- that existed around the same time, less than 400 kilometers (250 miles) away from each other," said lead author Pontus Skoglund. "After comparing our data to modern human populations in Europe, we found that the Stone Age hunter-gatherers were outside the genetic variation of modern populations but most similar to Finnish individuals, and that the farmer we analyzed closely matched Mediterranean populations." The data paints a picture of a migration of farming cultures that brought their planting and sowing expertise and eventually mixed with locals, teaching them how to grow their own food. "The Stone Age farmer's genetic profile matched that of people currently living in the vicinity of the Mediterranean, on Cyprus, for example," said Skoglund, a graduate student at Uppsala University in Sweden. "The results suggest that agriculture spread across Europe in concert with a migration of people," added Skoglund. "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." Co-author Mattias Jakobsson, also of Uppsala University, said the two groups "had entirely different genetic backgrounds and lived side by side for more than a thousand years, to finally interbreed." The result is a modern-day European population that shows strong genetic influences from Stone Age immigrant farmers, though some hunter-gatherer genes live on, the researchers said. The study was funded by the Danish National Research Council, the Royal Swedish Academy of Science and the Swedish Research Council, as well as by private foundations.