I just really don't find the arguments plausible myself. Those who argue that humans and Neanderthals interbred are reductionist in my opinion. People don't just sleep with anything that comes their way. Heck, most humans won't have sex with a rather large proportion of other humans. So, how did all this modern human / Neanderthal hanky panky take place?
We don't find mixed communities. If you conjecture rape, then who was raping whom? If modern humans raped Neanderthal females and then even if for some strange reason they kept the child that child would end up in the Neanderthal community. Whenever that Neanderthal community died out (as they all did) the intermixed genes would go with it.
And if the idea is that Neanderthals raped human females then you've got several problems. (a) You have to assume the human community survived, or else again the Neanderthal genes would not make it into the human gene pool. (b) Why would the humans raise a hybrid?
I already spoke to this. Even today there are women over in India and China right now who are killing their babies just because they're girls. Humans do not raise the offspring 'just because it's there' (we like to pretend that nowadays in our culture, but that's because we've internalized a bunch of socialization).
And if it wasn't rape, if it was willing, then where are the mixed communities? Why would humans *want* to mate with Neanderthals? *They were ugly.* I mean, really, really butt ugly. I can't think of anything that we'd actually need them for. And one more point that is often ignore: we have no idea what their speech capability was, but it's a good bet that it was very noticeably different than ours, and no doubt a separate language.
So, the idea here is that humans moved in - warlike, suspicious humans - found a group of Neanderthals, decided to get together, learn a second language, and sing kumbaya after sex??
alchohol?
Maybe, if you got enough beer....
My anthropological studies are limited to bars and such, y'know, the mating rituals of Homo Trailertrash, but the one constant I always see in my subjects of observation is that the girls, they all get prettier the nearer closing time is. And a lot of them could be classified as "Neanderthal".
You can't base the argument on modern social norms. Although you could possibly be correct, your argument can't ever get beyond assertion. And there are plenty of exceptions to the rules you mentioned, so cultural exclusivity will always be full of holes.
But the key question remains, even if there was interbreeding, how could one entire line go extinct when it stretched across the Eurasian landmass?
Corollary question: When was beer invented? :-)