attraction is mostly gene based, but it's debated whether or not attraction can be learned (although you generally won't learn to become gay in the west. unless you spend time on tumblr)
the debate in attraction lies within tits, actually. lots of tribal societies allow them to hang out freely on both genders and all the guys have flaccid dongers but in the west, obviously, showing them in public is practically as taboo as showing your genitals in public because those in the west attracted to women, well, see them as loveually attractive.
the question is, have these tribes learned to ignore the boob or have we learned to notice the boob?