im sure this has been asked a billion times, but what is everyones opinions on why men have nipples?
A vestigal leftover from the fetus state before gender is determined visibly. Evidently for proper female nipples to develop they need to begin forming prior to the time in pregnancy when growth starts to visibly differ between genders.
Methinks Cecil’s explaination leaves a little to be desired. Men (and the males of virtually all other mammalian species) have vestigal nipples because, from an evolutionary standpoint, the cost of developing them is less than the cost of separating them into a different, sex-linking chromosome. Building a human being is like cooking a meal; you use the ingredients that you have in the larder, and if you have a limited selection of items you’ll tend to make dishes that use the same items, like using a half-cup of sour cream in your mashed potatoes and making a lemon cheesecake to use up the rest of the container. There’s really no reason to select against vestigal nipples–aside from a slight sensitivity they don’t present a vulnerabilty or require extra energy to build or maintain–and it makes the recipe that much more simple.
Remember, there’s no goal or intent behind phenotypical features; we don’t have fingers/thumb because they allow us to screw the tops off of beer bottles; we have screw-top beer bottles because we have fingers and an opposable thumb, and while that gives us an advantage over other animals that might otherwise occupy the niche of construction worker, data entry specialist, or knife-wielding homicidal maniac in a John Carpenter movie, it doesn’t make us more successful than snakes, sea otters, or duck-billed platypusses in their own niche.
I have to take issue with one of Cecil’s claims though, namely that “Actual lactation is rare–only a couple cases have been recorded.” It is not uncommon for boys in puberty to exhibit some small degree of lactation in response to stimulation, demonstrating that while the milk glands are undeveloped, they are functional. (In the case of gynecomastica, male breasts may become partially or fully developed, although again there are rarely sufficient hormones to cause productive lactiation.)
So, we have nipples for the same reason we have appendicies; 'cause it’s cheaper and easier to let them exist than to remove them.
Stranger
Quote from
http://www.articlebiz.com/article/2862-1-the-sexual-body-feelings-and-erogenous-zones-of-men/
The nipples of a man are important erogenous zones, and a man has tits just as a woman, although the tits of a man are smaller and flatter that those of a woman. Actually a man has all the structures that a woman has in his breasts, but they are not developed to have a milk producing capacity. This means that a man’s breasts have the same erotic capacity as the tits of woman. A man’s nipples also have an erective capacity. They rise and get hard upon stimulation. When stimulating a man’s breasts, take hold of the breast with your whole hand, warming it inside your hand, and massaging it gently by gripping movements. To stimulate the nipples, massage gently around the nipples with a finger tip. Also squeeze the nipples with your fingers, varying the intensity from the very gentle nip to some harder pressure.
Are you seriously suggesting that eroticism is the evolutionary advantage that promotes the retention of male nipples?
If so I’d like very much for you to expand on the actual mechanism by which this promotes the sustaining of the species. If not, I fail to see how it relates to the OP.
The Op asked why men have nipples. The Op did not ask how male nipples sustain the species nor the evolutionary advantage of nipples.
Evolutionary reasons are the only correct answers when asking why a creature has a given feature–either the feature confers an advantage or some sort, or it fails to be a disadvantage. Nipples may very well be an erogenous zone in both sexes, but that is not the reason they exist.
Surely I do not have to spell out the fact that there is a connection between sexiness in humans and evolution. Evolutionarily speaking humans are the most successful mammal ever. Any connection between that and the fact that humans are the most sexual of all mammals, I wonder. Why do we have sex hundreds/thousands of times just for one pregnancy? Women have orgasms. Men have nipples which are erogenous zones. Yada yada yada.
Surely you can see that these kind of answers -“A vestigal leftover from the fetus state before gender is determined visibly” are rubbish. How does that explain anything? A sexual answer is surely more scientific.
Probably not. Look up bonobos, also known as pygmy chimps, sometime. In any case, I fail to see how males having erogenously-sensitive nipples has any effect on reproductive success. Male nipple stimulation is NOT required for arousal, erection, ejaculation or any other part of the reproductive cycle. I dare say most, if not virtually all, men can perform quite adequately without it, in fact.
Your argument could be used to say that women’s nipple stimulation is not required for the reproductive cycle. But women’s nipples are an errogenous zone. Why? It is not needed.
Yada yada yada indeed. Both the second and third statements are baldly untrue. Humans (Homo sapiens) exist as a distinct speicies only back about 200,000 years when they were confined to certain geographical regions of one continent; even the late hominid australopithecus is only ~3 million years old; there are many continuous mammilian lineages–narrow groups within a genus–which pace that by an order of magnitude and which are distributed across continents. Nor are humans “the most sexual of all mammals” as a visit to the Primate House at any zoo will indicate. It is also a mistake to equate the sexual behavior and attitudes of modern humans with prehistoric and protohuman populations; we have little information on the sexual appetites of prehistoric man, but it seems unlikely that they engage in the nearly continuous sexual contact that is endemic to the lifestyle of the bonobo chimp.
Response to sexual stimulus may have some small bearing on sexual selection (i,e. competition between members of a speceis for the attentions of a member of the opposite sex) but given the fact that human males are readily aroused regardless of contact with the nipple area, nor does this seem to be a feature that females seek out as being an area of critical attraction, it is unlikely that it plays any significant evolutionary role. This is certainly the case in other mammals (dogs, cats, bears, et cetera) where vestigal undeveloped nipples exist but play absolutely no role in sexual selection.
The nipple and associated area is a terminus for a collection of nerve endings which serve to benefit a nursing female by stimulating the production of hormones needed to produce milk. That they also exist in the male–in what is again a somewhat underdeveloped capacity–has every indication of being entirely coincidental; again, it’s an artifact of efficiency (from a gene coding point of view) to building both models from the same basic print and turning on or off different features during development via hormone control.
There is no conceivable argument for male nipples providing any significant evolutionary advantage. The fact that nipples are an erogenous zone is a convenient happenstance, not a design feature.
Stranger
Do males of other species have nipples? If so, that would seem to back up the idea that has nothing to do with human male sexuality and everything to do with genetic efficiency.
Many, if not all, male mammals have rudimentary or vestigal nipples (though I do not encourage you to attempt to research this by typing “nipple male dog” in Google :eek: ).
Although not about male nipples per se, Steven J. Gould and Richard Lewontin made the case in their landmark paper that not every trait has an immediately adaptive explaination. It’s quite possible for neutral traits–say, having a different colored patch of skin–to propogate not on their own merits but simple by being coincidentally linked with successful traits. Even if you take the gene-centrist point of view, you have to acknowledge that traits are passed on or not determined not by their direct benefit to the carrier but by their predisposition to being reproduced. One might argue that “slanted eyes” (i.e. an epicanthic fold) is a superior adaptation for living in Japan by noting the predominance of that trait, even though (while it may have at one point benefited residents of the Central Asian plains) it offers no real survival or advantage to the people of Japan. (It does, however, offer a reproductive advantage, insofar as Japanese people are culturally pressured to marry like rather than mix with gaijen.)
It is a mistake to assume that every phenotype offers an evolutionary advantage; although with an engineered product, we can (generally) assume that efficiency of design means that every button, lever, and wiz-bang has a specific and necessary purpose, in the game of natural selection efficiency means starting with some arbitrary organism and eliminating or modifying phenotypes to best fit the pressures of a specific habitat, with no deliberate intent to remove features that are deprecated but which don’t inhibit the carrier from being successful at reproduction.
Stranger
Oh, yes. In fact, I can’t immediately think of a mammal whose males don’t have them–with the possible exceptions of marsupials and monotremes.