Europe’s genes reveal mysterious “genetic turnover” 4,500 years ago

Apr 24, 2013
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The origins of early Homo Sapiens in Europe have been further revealed in new DNA exploration of skeletal remains, exposing a sudden "genetic turnover" roughly 4,500 years ago that indicates a massive population change. Previously, scientists had believed European settlers had arrived roughly 7,500 years ago and modern Europeans descended from them; however, research led by the University of Adelaide indicates a mysterious event more than four millennia ago saw that group wiped out and replaced with the true European ancestors, origins unknown.

"The population moves in around 4,000 to 5,000 years ago, but where it came from remains a mystery" director of the Australian Centre for Ancient DNA, Alan Cooper, said of the findings, published in Nature Communications this week. "We can't see anything like it in the areas surrounding Europe."

The study used extracted mitochondrial DNA from 39 skeletons that had been found in central Germany and Italy, ranging from as young as 2,500 years old, to as old as 7,500 years. From those samples, comparisons with the "haplogroup H" mutations found in up to 45-percent of modern Europeans were made.

Previous theory had led to expectations that the mutations would be widely carried. However, in actual fact there was evidence of multiple waves of different groups, shaking up a period that had hitherto been presumed to be stable. Genetic markers from earlier remains did not match up with counterparts in modern groups.

"We don't know what happened or why, and [the mid-Neolithic] has not been previously identified as [a time] of major change," Cooper said of the surprise findings. However, other researchers - not connected with this study - have pointed out that there are many archeological changes approximately 4,000 years ago.

That includes less evidence of the sort of long structures the older settlers preferred, and changes in the tools they used.

"What is intriguing is that the genetic markers of this first pan-European culture," Cooper said, "which was clearly very successful, were then suddenly replaced around 4,500 years ago, and we don't know why." One possibility is climate change, though Princeton University archeologist Peter Bugucki argues it's unlikely to be the sole cause.

"It looks like the whole system of agricultural settlement that got established with the [original settlers] ran its course through the fifth millennium and something caused people to change" he told National Geographic. After that point, further genetic diversity was introduced as "a series of incoming and expanding cultures from Iberia and Eastern Europe" arrived, Dr Wolfgang Haak, co-author of the study, said, "through the Late Neolithic [period]."

[via National Geographic; via BBC]


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