Some Europeans are descended from neolithic farmers

If true, northern Europeans share essentially the same genetic makeup as their bison-hunting forefathers.

According to Oxford University's Ryk Ward, the genetic data fits in surprisingly well with archaeological clues.

"Around 20,000 years ago, the population of Europe was forced to retreat into an area where there were no glaciers," says Professor Ward of the Institute of Biological Anthropology.

"From that population base, a very small number of individuals then became the ancestors of the current [northern] European population."

Out-of-Africa

He says it is impossible to specify exact numbers, but he believes that about 1,000 individuals gave rise to the modern northern European gene pool, and possibly as few as 50.

According to the joint US and UK team, northern Europeans diverged from their African roots as recently as 27,000 to 53,000 years ago.

"From a genetic standpoint, this is the first evidence that such a bottleneck occurred in Europeans," he told BBC News Online.

The evidence comes from a study of stretches of human DNA that contain individual variations of just a single letter in the genetic code.

Individual variation

Scientists are interested in studying these tiny molecular differences (single nucleotide polymorphisms or SNPs) because they could explain why some people are more susceptible to common diseases than others.

The emerging genetic picture of Europe

10 male lineages gave rise to the vast majority of Europeans Seven female lineages arose some 50,000 years ago 80% of Europeans are descended from Paleolithic hunter-gatherers

But they also provide a tool for studying our genetic history, by measuring the amount of shuffling of human DNA that has occurred over time.

Many scientists believe that humans arose in Africa, and then spread and conquered the rest of the world.

But during this long journey, the genetic history of the human race underwent a series of twists and turns.

Northern Europeans share SNPs with the Nigerian population, says Eric Lander of the MIT/Whitehead Center for Genomic Research in Cambridge, Massachusetts.

But he says the European samples show large clumps of unshuffled genetic material, suggesting a recent breeding bottleneck.

The study is reported in the 10 May issue of the journal Nature.