Why Do Men Have Nipples?

Almost all mammals have nipples. Feeding babies through the navel, and then from the breasts, instead of using a yolk like birds and reptiles, is the evolutionary trait that has made mammals so successful. Caring for children to the age of 20 while intelligence develops is humans winning recipe. But why do men have nipples when only females nurse?

“because the “female template” is the default for humans, the question is not why evolution has not selected against male nipples, but why it would be advantageous to select against male nipples in the first place:

The uncoupling of male and female traits occurs if there is selection for it: if the trait is important to the reproductive success of both males and females but the best or “optimal” trait is different for a male and a female. We would not expect such an uncoupling if the attribute is important in both sexes and the “optimal” value is similar in both sexes, nor would we expect uncoupling to evolve if the attribute is important to one sex but unimportant in the other. The latter is the case for nipples. Their advantage in females, in terms of reproductive success, is clear. But because the genetic “default” is for males and females to share characters, the presence of nipples in males is probably best explained as a genetic correlation that persists through lack of selection against them, rather than selection for them. Interestingly, though, it could be argued that the occurrence of problems associated with the male nipple, such as carcinoma, constitutes contemporary selection against them. In a sense, male nipples are analogous to vestigial structures such as the remnants of useless pelvic bones in whales: if they did much harm, they would have disappeared.” -wikipedia

This is maybe hard to understand and it sure is easy for creationists and the like to willingly misunderstand, but it’s not very complex. If an individual has a negative trait, like being blind, then that individual is more likely to die before being able to reproduce, either from falling, not being able to find food or being eating by a predator. Even bad mutations can get lucky though, so temporarily, unlikely populations do exist. But here is the crux of the matter: Being able to see really well does not give you more children. Evolution only works one way, it kills the misfits, it doesn’t reward the well-adjusted. By inference, the well-adjusted are rewarded since they’re left unkilled, but natural selection doesn’t premier positive traits, it only weeds out the bad ones. In the long run, only the best remain so it’s easy to make this mistake. Survival of the fittest is actually only an indirect consequence of the killing of the unfit, or the Impotence of the Weak, or what have you. It’s this mechanism that answers the question: “Why have we not evolved to perfection yet?”. Because mutations are random and the bad ones are removed and perfection only happens if all the perfect mutations randomly appear instead of the ones that aren’t perfect, but good enough for continued procreation. This is an easy relationship to remember and if you keep it in mind in discussions about evolution, you will be able to spot the flaw in many arguments.

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2 Responses to “Why Do Men Have Nipples?”

  1. Gledwood Says:

    apparently 50% of men have sensitive nipples. the other 50% aren’t sensitive. or something. i remember watching a film of a bloke getting a baby crocodile to bite down on his left nipple… his nipples most certainly seemed to be sensitive. he didn’t half yell out loud!!

  2. Lura Amberson Says:

    Hi, I ran into your page from reddit. It’s not something I would normally read, but I liked your spin on it. Thanks for making a piece worth reading!

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