I never said homo-sapien and neanderthal matings were common. What I said was there was more evidence of mating between the two than of systematic extermination by homo-sapiens as was suggested by another poster.Well I am not debating the Neanderthal inbreeding. But contrary of what you say it was in fact extremely rare. For the coexistence some millennia is nothing comparing to a species lifespan, so for me there is no reason than could get the other species to got extent. Environmental change don't explain it. The propagation of
Homo sapiens has a lot do with it.
What I also said was that for the most part the two avoided each other more than likely. Since homo-sapien communities were larger and not isolated from each other, its no surprise that homo-sapiens would mate with other homo sapiens because that was who they were in contact with on a daily basis. This was especially true as the Neanderthal population dwindled being driven further away and neanderthals retreating into isolated clans that resorted to inbreeding for lack of contact with outsiders. As the neanderthal population became scare, naturally there would have been a lack of contact with homo-sapiens. But during instances when they did meet and interbred either through mutual mating or rape they did produce fertile babies and this is indicated by genetic evidence today.