Stone age farmers and hunters co-existed in Europe for centuries but kept their distance, researchers say, rarely crossing cultural boundaries to find a mate.
Genetic studies of ancient bones suggest when farmers moved from the Near East into Central Europe about 7,500 years ago they were met by indigenous hunters and gatherers not exactly pleased to see them, the scientists said.
For some 2,000 years, the genetic work showed, these distinct groups apparently maintained separate cultures.
"We don't really know who set up those social boundaries, so we don't know if it was the farmers who didn't mix with the hunter gatherers or if it was the hunter-gatherers who wanted to stay by themselves," lead study author Ruth Bollongino, a biologist at the University of Mainz in Germany, told The Washington Post.
"Or maybe it's both groups that wanted to keep their own identity."
Eventually the hunter-gatherer communities died out or adopted the agricultural lifestyle, the researchers said.
Scientists have long wondered what impact both groups had on the gene pool of modern Europeans.
"Neither hunter-gatherers nor farmers can be regarded as the sole ancestors of modern-day Central Europeans," study team member Adam Powell, a population geneticist at the JGU Institute of Anthropology, said. "European ancestry will reflect a mixture of both populations, and the ongoing question is how and to what extent this admixture happened."