conversely can any man here really say he found womens big butts attractive in childhood ? Mostly children and pubescent boys (unless they are exposed to modern porn-and so value assignment) think of breasts a lot, due to being breastfed. So that value (and dopamine) is strong for the breast !
But then gain some sexual experience and all of a sudden womens rears become interesting, because its become linked to the pleasure of sex.
there are desmond morris theories of lordosis and breasts being attractive, at a fundamental visual level, but has that really been tested ? In primate lordosis the female is sending out a lot of ovulation scents, so that could be the initial stimulus trigger, plus the vagina is extra large and bright anyway. then after that the brain can associates future lordosis with pleasure even if there is no scent perception.
When you think about it, breasts and big butts are really just functional. And do teenage men really care about signals of womens fertility ? They just want to hump and dump mostly.
there isnt actually a brain area devoted to breasts or other sexual organs except the sex responsive areas of the hypothalamus, which some researchers linked to pheromones.