Analysis of the oldest known European DNA, from the 37,000-year-old body of a man found in southwest Russian 60 years ago, shows Europe's genetic diversity stretches back at least that far, researchers say.

It also demonstrates widespread intermingling among peoples during Paleolithic times, much further back in time than previously thought, and that the resulting diversity survived the last Ice Age, they say.

The researchers analyzed the DNA from a leg bone of a hunter-gatherer discovered in Russia at a site known as Kostenzi in 1954, considered one of the most ancient specimen of a modern human ever uncovered from Europe.

"One of the surprising things is that if you go 37,000 years back in time, you find all the major genetic components that are present in modern Europeans," says Eske Willerslev, a geneticist at the University of Copenhagen.

While some geneticists have identified in other human remains found in Europe separate genetic strains from hunter-gatherer peoples and later peoples involved in farming, they are all found together in the Kostenki remains, says Willerslev, co-author of a study published in the journal Science.

"You wouldn't predict if you go back to one of our earliest individuals, all the components of modern Europeans were already there," he says.

Finding such a diverse and complex genetic mixture in remains so old suggests Stone Age Europe may have been home to a single population, genetically similar, stretching from Northern Europe to the Middle East.

This is in contrast to previous beliefs that held the genetic makeup of Europeans was the result of separate peoples encountering each other and occasionally mingling or interbreeding.

"Rather than separate populations moving into each others' areas and having sex with each other," Willerslev says, "there was a single 'meta-population' having sex -- or exchanging genes -- in a complex and heterogeneous way."

The findings lend support to current theories of what happened when humans began to migrate out of Africa.

Genetic evidence suggest three major waves of migration; a first group that ended up in present day Australia and the islands of the Pacific; a population moving into East Asia; and a third wave of western Eurasians who became the Europeans.

The DNA of the Kostenski man is unrelated to either of the first two groups, suggesting the migrating populations diverged at least 37,000 years ago, the researchers say.

The findings suggest the genetic history of Europe's past is more complicated that was believed, Willerslev says.

"We all thought you could sequence these bones and come up with a simple story. This paper really shows things are not as simple as people thought they were," he says. "Europe has always been a melting pot."