Many male humans are sexually attracted to the breasts of female humans. Is there an evolutionary reason for this?

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    $\begingroup$ They aren't so much if they are not hidden, i.e. rainforest and old african tribes. $\endgroup$ May 26, 2019 at 7:00
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    $\begingroup$ breasts are a signal of fecundity, puberty, age, fitness... plus, if you look at chimp and oprang breasts, they are pretty similar when breastfeeding. $\endgroup$ May 27, 2019 at 12:40
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    $\begingroup$ This question is quite misinformed and problematic. 1. It doesn't mean anything to be sexually attracted to a non-reproductive part (like secondary chars. described below). 2. Attraction (perhaps 'mate preference' is better) is not reductionistic, as implied, where the opposite sex is reduced into parts. 3. Sexual selection worked differently across human populations. 4. There is definitely no basis in evolution for the question. As written below, there are evolutionary reasons for breasts and hypotheses as to why they unique in humans, but this is very different than what was asked here. $\endgroup$ May 28, 2019 at 13:20
  • $\begingroup$ @Chris Moore How could this question be reworded to make sense? Being outside the field of evolutionary biology, I don't understand your critique. I think this comment could be usefully expanded into a great answer while still addressing the general question being asked even if it is misinformed. $\endgroup$
    – syntonicC
    May 28, 2019 at 13:46

2 Answers 2


Short answer, we don't know.

There are several competing hypotheses but they are all nearly impossible to test. Behavior often suffers the same problem as testing, we can come up with a hypothetical reason but since we are the only organism that does it, we have no good testing options. We can't put people in controlled conditions for generations and see if their preferences change. Secondary sexual characteristics in general have problems with testing. Because there is no good way to differentiate reasons for a behavior. We still don't have a great consensus on why secondary sexual characteristics in humans exist, likely because many explanations can be true at the same time, humans have very complex behavior even in out instinctual behavior. It could just be a quirk of neurochemistry caused X to be attractive, followed by run away selection, and that by itself would create a selective advantage. It can be really hard to test why a preference would arise unless the advantage is obvious because the different hypotheses all behave the same way in practice.

Possible answers include:

-lifting the nipple away from the body to make suckling easier for flat-faced human babies with protruding noses.

-runaway sexual selection (which is also a component of many others as well).

-cryptic signalling of ovulation and/or pregnancy.

-all of the above

Paper reviewing all the different hypotheses

  • $\begingroup$ @kmm how is that. $\endgroup$
    – John
    May 25, 2019 at 23:22

This is a hypothesis that I found in Desmond Morris book, The naked ape.

Basically, humans transit from a rear-penetration position to a frontal-penetration position. In this transition, the sexual clue performs by buttocks was perform now by breast.

In short, according to Morris: breasts are sexual clues because they look like buttocks.

  • $\begingroup$ Please, if downvote, explain in a comment why. I understand that this could be a controversial hypothesis, as such, in need to be discussed. $\endgroup$
    – heracho
    May 28, 2019 at 17:21
  • $\begingroup$ theguardian.com/science/2017/sep/24/… $\endgroup$ May 30, 2019 at 1:45
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    $\begingroup$ Very good analysis of Morris book. It makes clear that it is loaded of misogynists views. Whit respect for the subject in the discussion, we read: Did boobs replace bums as a sexual signal when we became upright? I don’t know, but the point is that no one does. According to this, there is no scientific evidence for the hypothesis (nor to confirm or denied it). $\endgroup$
    – heracho
    May 30, 2019 at 14:01

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