In a 1951 book called Patterns of Sexual Behavior by Ford and Beach, it states that breasts are only sexually important in 13 of 191 cultures. 13 cultures also reported breast stimulation during sex, only 3 of those cultures overlap with the sexually important cultures. Large breasts were preferred but areola size and color were highly idiosyncratic.

Why did breasts get bigger from primates to humans? One theory is to prove to males that the woman has enough nutrition to be pregnant. The other theory is moving the “ready for sex” indicator from behind to the front due to bipedal walking.

Its known that oxytocin is released during breastfeeding assumed to be for bonding with a baby. Researchers think men through evolution are hijacking this neural circuit to make themselves more attractive. Recent studies have proven that nipple stimulation activates the same part of the brain as clitoral and vagina stimulation.

Why did this evolutionary change happen? Two theories are that humans are monogamous, unlike 97% of other mammals. And humans have sex face to face giving greater access to the breasts.