It now seems pretty clear that about 50,000 years ago modern humans did interbreed with Neanderthals. As Matt Ridley points out, it has been known for some time that non-Africans share 1 to 4 per cent of their genomes with the extinct Neanderthals, but this could have been due to genetic differences between the various African populations from which modern humans arose. New research, however, seems to undermine the so-called 'population substructure' theory.
For, according to Dr. Svante Paabo and his colleagues, the last gene flow from Neanderthals into Europeans most likely occurred between 47 and 65 thousand years ago, too late for the substructure theory. And during this time there were periods when Neanderthal and modern human populations were living in the same areas (in what is now Israel, for example).
It's no big deal, I suppose, but it certainly changes the way one sees Neanderthals (no longer quite the lumbering losers or tragic victims - as the old stereotypes had it).
And it seems that mating between modern and pre-modern populations was a common occurrence.
For example, Ridley points out that there was almost certainly interbreeding between the modern people who populated South East Asia and Australia and the pre-modern Denisovans.
As he puts it, 'when modern people spread around the Indian Ocean, they too encountered a distantly related human species and dallied with them under the palms.'