I think it's a valid question. I often wonder what the cutoff is for how something determines whether another entity is of the same species (ie, something I have sex with vs something I eat). For instance, you could go off of looks, but then why would a german shepherd try to have sex with a pug? There seems to be some sort of ingrained biological threshold for what is a compatible mate and what isn't. Determining that threshold for various species is interesting to me.

> There seems to be some sort of ingrained biological threshold for what is a compatible mate and what isn't.

Clearly, Neanderthals were very much within the acceptable mate boundary, the question was whether that occurred despite recognizing them as “other” or not.

Ok but the question is assuming they have a concept of species, presumably with a bright line, and then are using that to determine whether or not to have sex. Which is circular (as well as absurd on so many levels).

That said, I'm sure they had some concept of "differentness," which would lie on a spectrum, rather than the black and white way the above poster described it.

Humans may, for instance, find people of different races to be less attractive in general. But exceptions can be made. I imagine if you are desperate enough, you widen the pool of acceptable candidates. I have no reason to think it was very different back then.

> There seems to be some sort of ingrained biological threshold for what is a compatible mate and what isn't.

Perhaps in a general sense yes, but across millions of people across tens of thousands of years, there will always be outliers who'll mate with anything with two legs.