Why do humans want to have sex with attractive people?

The learned researcher Susan James (Vote #1: Susan James’ answer to Why do humans want to have sex with attractive people?) is of course right in the evolutionary selection angle, and even more right in the cultural situatedness of attractiveness. The body-ideal of Botswana sure isn’t the ideal of the 2016 US, which wasn’t the ideal of 1956 US.

But there’s a bit of semantics being missed here. It’s not that the notion of attractiveness is preexisting, and people want to have sex with people bearing that characteristic. There is physical fitness or suitability for child-bearing, which has visual correlates; in fact Susan has pointed them out in previous answers (I think;, though Quora Search, so I can’t find them). So breasts or butts (or six packs) tend to correlate with attractiveness.

But attractiveness is also culturally determined; there are plenty of cultures in which big butts or physical fitness are not prized as attractive. In fact attractiveness is defined the other way around. Attractive people are defined as those people that humans (in that particular culture) want to have sex with.

(And that also helps you with LGBTI+, which a narrowly evolutionary approach doesn’t.)