A research group at Bonn University, Germany, and international collaborators discovered a novel receptor, which allows the immune system of modern humans to recognize dangerous invaders, and subsequently elicits an immune response. The blueprint for this advantageous structure was in addition identified in the genome of Neanderthals, hinting at its origin. The receptor provided these early humans with immunity against local diseases. The presence of this receptor in Europeans but its absence in early men suggests that it was inherited from Neanderthals. The results have been published in advance online in the Journal of Biological Chemistry. The printed edition is expected in a following issue.Whether or not it predates Neandertals will never be known but the fact that it has time-depth back that far suggests that this receptor evolved separately from the incipient modern humans and that the interbreeding between the two was sufficient enough for it to take hold in some populations of modern humans. The report also notes that this receptor is very rare in Sub-Saharan Africans but is present in at least two-thirds of Europeans.
I think we are just scratching the surface in terms of determining how much interbreeding went on between Neandertals and modern humans. It is clear, judging from each new study, that the species lines are becoming more and more blurred.