A group led by Svante Paabo of the Max Planck Institute for Evolutionary Anthropology analysed the lengths of segments of Neanderthal DNA in modern Europeans to determine when Neanderthal genes may have mixed with those of modern humans. The date they came up with for the gene flow was 37,000 to 86,000 years ago, and most likely 47,000 to 65,000 years ago. This date strongly suggests there was interbreeding when Homo sapiens was moving from Africa encountered populations of Neanderthals in the Middle East.
     Another group determined that modern humans gained from Neanderthals a family of genes that helps the immune system fight off viruses.

Edited from National Geographic Daily News (12 October 2012)