An analysis of 5000-year-old DNA taken from the remains of four Stone Age humans excavated in Sweden is helping researchers understand how agriculture spread throughout Europe. According to Pontus Skoglund from Uppsala University in Sweden and colleagues, the practice of farming appears to have moved with migrants from southern to northern Europe.
Agricultural know-how wasn’t the only thing that early European farmers introduced to the region, though. Based on this ancient genetic data from Sweden, Skoglund and the other researchers suggest that Europe’s first farmers eventually mixed their genes with the hunter-gatherers who lived there—a relationship that set the stage for today’s modern European genome.
“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 (249 miles) away from each other,” said 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 researchers reported their findings in the 27 April issue of the journal Science.
“When you put these findings in archaeological context, a picture begins to emerge of Stone Age farmers migrating from south to north across Europe,” said Skoglund. “And the result of this migration, 5000 years later, looks like a mixture of these two groups in the modern population.”
Mattias Jakobsson of Uppsala University discusses the Science research. | Video courtesy of Simon Ydhag, Uppsala University
Most experts agree that the agricultural way of life originated about 11,000 years ago in the Near East, before reaching the European continent some 5000 years later. But this new study should help scientists understand the impact of the agricultural revolution on human diversity, the researchers said at a 26April press conference in Uppsala, Sweden.
“Anthropologists in Europe have puzzled over whether the original Paleolithic hunter-gatherers were replaced by farmers or whether they adopted the methods of the new arrivals,” explained Andrew Sugden, deputy editor of biology at Science. “The evidence from the ancient DNA shows significant differences with respect to their relationship with modern European populations. And that, in turn, suggests distinctive and separate populations of hunter-gatherers and farmers, and that migration and mixture were then responsible for the spread of farming.”
Skoglund and his colleagues performed their analysis with the ancient remains of three hunter-gatherers who were associated with the Pitted Ware Culture and excavated from the island of Gotland, Sweden, along with those of a farmer, who was associated with the Funnel Beaker Culture and excavated from Gökhem parish, Sweden. Both cultures were named after the characteristic pottery that they left behind, and researchers use such artifacts to determine where and when the cultures existed.
“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, also 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.”
The ancient hunter-gatherers had a distinct genetic signature that was similar to that of today’s northern Europeans, while the farmer’s genetic signature closely resembles that of southern Europeans, according to the researchers. Interestingly, these ancient genomes don’t share many similarities with modern-day Swedes, despite their discovery in Sweden.
(l-r) Science authors Jan Storå, Mattias Jakobsson, Pontus Skogland, and Anders Götherström with AAAS at the 26 April press conference. | Photo courtesy of Uppsala University
“The fact that the hunter-gatherers are most similar to Finns, Orcadians, and other extreme-northern populations suggests that they were indeed the last major part of the Mesolithic meta-population that populated large parts of Europe before the early farmers appeared,” said Anders Götherström of Uppsala University. “And the fact that the farmer is most similar to southeastern Europeans makes sense too, as that is from where the spread of agriculture north and eastward started.”
“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.”
“We now see that it was people who brought farming across Europe,” Jakobsson concluded, “instead of a culture that spread the ideas of farming through word-of-mouth.”
The researchers suggest that Europe’s early, intrepid farmers traveled north across the continent, settled in the northern regions, and eventually mixed with resident hunter-gatherer populations. Consequently, they say, the genomes of most modern Europeans were likely shaped by this prehistoric migration that first brought farming to the continent.
“One of the important things to stress about this work is the interdisciplinary nature between archaeologists, molecular geneticists, and population geneticists,” added Sugden. “This is an increasing trend that we’re seeing in science these days, and it’s a very welcome one.”
Listen to the research team discuss its findings at a 26 April press conference in Uppsala, Sweden.
Read the abstract, “Origins and Genetic Legacy of Neolithic Farmers and Hunter-Gatherers in Europe,” by Pontus Skoglund and colleagues.
Listen to a Science Podcast interview with Mattias Jakobsson.