For years, scientists have argued over over the extent to which present-day people descended from Europe's initial peopling of hunter-gatherers some 35,000 years ago in comparison to a migration by Near Eastern farmers that occurred in roughly 4000 BC.
However, a new analysis of DNA remains from 39 ancient skeletons from the Mitelelbe Saale region of Germany reveals the former group's gene's were all but erased by later migrations, including but not limited to the latter group of farmers.
However, the DNA analysis told another story as well - one researchers weren't expecting.
While sequencing the mitochondrial genomes of the skeletons, which span 3,500 years from the Early Neolithic to the Bronze Age, scientists found a sudden disappearance of the genetic signatures of the former group. In all, only 19 percent of skeletons' examined belonged to the Early Neolithic clan.
The genes found in the subsequent group, those of the Middle Neolithic, however, remained very much in tact through the years and closely resemble the genetic makeup of the people who live there today.
All of this, scientists say, points to a major population upheaval around 4,000 BC. And whatever that upheaval was, not only was it nearly complete, it was sudden.
"The genetic markers of this first pan-European culture, which was clearly very successful, were then suddenly replaced around 4,500 years ago, and we don't know why," the study's co-author Alan Cooper from the University of Adelaide in Australia said, according to BBC News.
But, he said, whatever it was, it was "major," and "the hunt is now on to find out what that was."
One possibility, Cooper suggests, is the migration of the Bell Beaker people whom many believe moved east from the Iberian Peninsula around the year 2800 BC. However, whether this group instigated the major genetic change or only contributed later, is not clear.