The Guardian out of the U.K. received a question from an animal science student asking about the nature of breasts. The response, from columnist and evolutionary psychology expert Carole Jahme, is thought-provoking both scientifically, historically, and anthropologically speaking.

Here’s the question:

I’m an animal science student and during our mammogenesis lecture a professor brought up the obvious, but seemingly overlooked notion of the size of the female human breast. Other species do have obvious teats and great apes have breasts, but humans are at the extreme end – obviously not all – but it does make one wonder on a selection and genetic level, why?

Jahme’s response illustrated some key points. Below are her pearls of wisdom on the uniqueness of human women in that their breasts are always present.

In non-human primates (and other mammal species) a full breast is a clear indication the female is suckling young. Not so in humans. In addition, females in early adolescence can start developing a breast before menarche and females maintain breasts post menopause, so the full breast is not a reliable indicator of fertility. Neither is size an indicator of milk production – bigger breasts don’t necessarily produce more milk. It is the symmetry of the breasts that indicates the phenotypic quality and fitness of the individual female, not the size.

You know, it had never before occurred to me that you only see noticeable breasts on female animals while they are giving their young sustenance. After their pups or cubs or whatever are weaned, the visible, uh, teats disappear. Not so with humans despite our breasts being kind of superfluous for the majority of women. I mean, we all have them, from teenagers to the elderly … and there is no real purpose. Uh, except for the sexual pleasure thang, which I suspect is noteworthy in women of all ages. Jahme addresses that, too:

The sex appeal of rounded female buttocks and plump breasts is both universal and unique to the human primate. Fertile women tend not to store fat around the abdomen, so the waist of a fertile female is usually slimmer than her hips.

Wow, this goes right along with the move toward having a few extra pounds—not emaciation, not obesity, just a healthy-looking woman. Odd that, according to Jahme, this is what men really want (and what has been proven the most healthy) as opposed to the skinny “ideal” many of us try to hold ourselves to.

It has been widely theorised that the plump buttock and bosom of modern women are sexual ornaments, selected for by ancestral males. Seen from a distance the adult female form, either from behind or from the front, can be recognised as distinct from the male of the species. An hourglass figure, plus youthfulness, would have attracted male hominids looking for mating opportunity. The hourglass figure remains attractive to modern males. Over the centuries females attempting to increase their mate choice have dressed to exploit this shape (corsets, bustles and wonder bras). If ancestral males had not shown a preference for the mutation producing symmetrical, plump bosoms, modern women’s chests would resemble the flat thoraxes of the other apes.

I suspect that breasts will always be a topic of conversation, whether in a sexual manner, breastmilk recipes, or even cosmetic nipple surgery.

What exactly is the obsession with the female breast? Is it a sexual thing, the almost-mystical nourishment of babies, both, or something even greater?

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