I suspect that neanderthals are actually modern humans.
LOL! Wouldn't that put the cat amongst the single origin pigeons?
Seriously. What would the implications be? If all humans have a single origin (aka out of Africa or Asia or whatever), wouldn't you expect sub-Saharan Africans and Neanderthals to share at least some DNA besides the basic stuff that all hominids share, I mean?
If Neanderthals are a different species than H. Sapiens, shouldn't their offspring be like mules? And the fact that the offspring are living...doesn't that mean that Neanderthal is possibly a sub-species rather than a different species?
This is why I love genetics. So many wonderful possibilities to explore...