any other female of any animal species with breasts doesn’t really ‘develop’ them unless they’re pregnant so why do human women develop breasts at puberty, just for them to develop even more during pregnancy?
In: Biology
Most of these answers are… unsatisfactory, so I’ll try my best. And just so you know, the science isn’t exactly conclusive either. It is also interesting to note that the pressures discussed below can also explain concealed ovulation.
So, once upon a time, women developed breasts during pregnancy and lost them after the youngens were weaned. Essentially, breasts were around at the same times a women was barren. Not a turn-on at all.
But, humans are a little more complicated than that. Humans are clever, and social, so sex required negotiation. It required relationships. As it happens, sex is also fun. So, men would have sex with infertile women in order to bond with them, and gain an advantage in the contest for her body once she was fertile again.
Then, of course, in evolution, there is the variation. The mutation. A woman with, if not permanent breasts, them breasts that stayed on for a little while longer, even into her fertility…
This woman had power. She would still have sex, sure, and as men didn’t know when she was fertile, she could take selection of her mate a little further into her own hands.
As such, she had an advantage in the contest to produce the best babies (as women’s bodies limit are the limiting factor in population growth, women themselves must focus on best babies, rather than mist babies). And such advantages are… advantageous. She would have had an edge over her sisters, and over time, her kind would predominate.
And in response, men too had to change. As a man turned off by breasts would now have a disadvantage in the male pursuit of ‘most babies’, the variation associated with attraction to breasts would have become more common.
And, as breasts became an established feature of female humanity, they would be under selective pressures themselves; larger breasts displayed good nutrition, and more importantly, the larger breasts would better show a woman’s symmetry (or lack thereof). So, breasts became larger. In different cultures, different tastes would emerge, and so sexual selection would bring above the large racial variation in breast shape, as well as in facial structure, colouration, etc.
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