But the idea that the human sex drive is primarily focussed on reproduction is hardly an established scientific fact. It's widely accepted a priori, but there is nothing to prove this. Even if the "reason" for the existance of the drive were solely for reproduction, the drive itself is not focussed on reproduction, by which I mean, men are not aroused by thoughts of reproduction, or contemplating reproduction when mounting a woman. He's interested in "getting some," not producing offspring, and in "coming," not fertilizing.

If you are not convinced, then why does a man find a woman attractive even if he knows she's not fertile (e.g., tubes tied)? Why would ANYBODY find post-menopausal women attractive?

Our enjoyment of tasty food may not appear to be driven by our appetite at times and perhaps never by our need to survive (without food we would die), but there is inevitably a link between these things. Our desire for sex and reproduction may not be in our consciousness at the same time but you can be sure that there is a link. We happen to overlay much of our desires with thoughts about them and thus the thoughts quite often (mostly in some cases) drive the desire, hence we may ignore what our body will possibly be telling us i.e. that the person is infertile etc. I'm not sure if the higher apes can get erections from thinking about other apes, it is possible, we certainly do. Presumably also we habituate and condition ourselves to respond to attractive women in general. I am no expert on sexual matters and have not studied this area much at all, just a little on beauty and attraction, however.

Moth