Physical attraction is largely Darwinian – whatever characteristics mark a person out as either good at surviving, good at producing/rearing offspring or generally successful will be attractive. Although that does change with social change.

Back before food was so easily available, “generously proportioned” women were the ideal, because it showed you had enough to eat for yourself and enough to support a baby. Now that food is plentiful but free time for exercise is scarce, the new ideal is to be slim/toned.

Elizabethans would use lead makeup to make their faces white, because pale skin was a sign of wealth – not having to labour in a field all day. Now that most jobs are inside a tan is a sign of enough wealth to go on holiday, sunbathe etc.

Then there’s the various fetishes people have, which is either inbuilt or comes from your formative years or something Freudian like that.