January 19, 2010 | 22
Agriculture emerged on the human cultural scene about 10,000 years ago, spreading rapidly through Europe from the Near East to the British Isles in about 4,000 years. But did this world-changing technology get disseminated via an expanding wave of industrious farmers or through word-of-mouth among local hunter-gatherer populations?
To help answer this much-debated question, researchers have peered into the genetics of modern Europeans for clues. Mark Jobling of the University of Leicester in the U.K. and his colleagues found not only that agriculture seems to have spread westward via a new group of Neolithic people from the Near East, but also that these new farmers were incredibly successful with the local ladies, leaving their genetic traces in their modern male descendents.
"We focused on the commonest Y-chromosome lineage in Europe," Jobling said in a prepared statement. The team analyzed a single haplotype, R1b1b2 (which is carried by about 110 million men in Europe today) from 2,574 European men whose families had been living in the same location for at least two generations. This common haplotype, however, is not randomly distributed across the continent. "It follows a gradient from south-east to north-west," he said. About 12 percent of men in eastern Turkey have it, whereas some 85 percent of men carry it in Ireland.
Others have previously speculated that this distribution was due to earlier, Paleolithic expansion from Africa. But Jobling and his fellow researchers asserted that it reflects a rapid, more recent genetic spread during the Neolithic—one that has a "striking" correlation with known Neolithic sites. "The geographical distribution of diversity within the haplogroup is best explained by its spread from a single source from the Near East via [Turkey] during the Neolithic," the authors concluded in their study, which was published online January 19 in PLoS Biology.
"In total, this means that more than 80 percent of European Y chromosomes descend from incoming farmers," geneticist Patricia Balaresque, also of the University of Leicester and lead study author, said in a prepared statement. "In contrast, most maternal genetic lineages seem to descend from hunter-gatherers."
How could these early European ancestors come from such different groups? "To us, this suggests a reproductive advantage for farming males over indigenous hunter-gatherer males during the switch from hunting and gathering to farming," Balaresque said. "Maybe, back then, it was just sexier to be a farmer."
Image courtesy of iStockphoto/wrangel