New finds in Europe shed new light on the relation between modern humans and Neanderthal people. Skeletons discovered in Pestera Muierii (Woman's Cave) in Romania, in Czech Republic, in Portugal presents signs of interbreeding between the two species.

Whatever might have been this relationship - if there was sporadic or continuous interbreeding - a new study suggests that this could have had a major impact on the evolution of the Homo sapiens' brain. Neanderthals, although long extinct, may have transmitted to our own species a lasting genetic gift. Till now, analysis of Neanderthal ancient DNA has revealed no signs of interbreeding.

Recently, a team at the University of Chicago reported that at least one gene, called microcephalin, involved in regulating brain growth (although the gene's precise role is not known), might have passed from the ancient species to ours. Analyzing the gene from 89 people from around the world, the scientists discovered that a particular variant of the gene, called haplogroup D, present in 70% of the world's population, appeared in modern humans around 37,000 years ago and seemed to have been favored by natural selection, quickly spreading inside the human populations.

Haplogroup D differed in so many bases from other variants of microcephalin that the geneticists estimated through statistical tests an age of a little more than 1 million years ago, long before Homo sapiens appeared. The team guessed that, most likely, prehistoric modern humans interbred with a now extinct hominid that carried haplogroup D, most likely Neanderthals. "The haplogroup was probably beneficial enough to spread quickly in modern human populations," says Bruce Lahn, a member of the research team.

Neanderthals must have been not as cognitively advanced as modern humans, and the researchers suppose that this gene variant might have conferred modern humans a better adaptation to the Eurasian environments that Neandertals had occupied long before the arrival of the Homo sapiens. This study is "the most compelling case to date for a genetic contribution of Neandertals to modern humans." said ancient DNA researcher Svante Pääbo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, who is going to search for the haplogroup D in his own studies on the Neanderthal genome.

Image: Left: Neanderthal skull Right: Modern human skull