New info on why guys have nipples

Dear Cecil:
I was just reading an answer that you supplied someone on why guys have nipples, but I was told by someone that all men are females for a short period of time in the womb and that is why they develop nipples. What’s the strait dope? ps: I love reading the Strait Dope! Keep up the good work!

Jared Diamond’s book - “Why Sex is Fun” mentions the interesting fact that we are one of about 11(?) mammalian species where the males can secrete milk. He points out that there is a greater statistical tendency towards this in species where greater male investment is required.
Although only a few of those species currently have the males helping out in any way, it’s possible they did at one time.

In any case, men have nipples due to being based on the same code as women. The reason we don’t have breasts (usually) is cause we get a different set of hormones in the womb.

Anyway - concerning your question…

Good answer, Kyberneticist!

Cecil’s column is Why do men have nipples?.

In reading Cecil’s column on the subject, I see that he says no mammalian species has male lactation. Does anyone have a copy of Diamond’s book handy? I’d swear he gives the example of a bat species where the males produce milk too.

And apparently, like female lactation, male lactation can be caused (sometimes) through mechanical stimulation. I seem to remember Diamond saying it was most common in a boy’s teens for hormonal reasons.

Men have nipples because it’s a lot of fun when women suck on them.

In TIME BANDITS, this was a point the argument of the Evil-Incarnate guy that God was incompetent: “Nipples for men?!! I thought this was brilliant wit when I was twelve.

But y’know, as a guy, I find I enjoy, um, having my papillae palpated.


“In my nightmares I am chased by algorithms”–crewman Celes, ST:V

Embroyology probably explains why males have nipples, but why they’ve remained so long on us probably has a lot to do with them being erogenous zones. Insert more turned on = more babies speculation here.

Personaly, I think they’re just a couple tiny reminders of the absurdity of life. That, and the Olsen twins.

all brains are origionally female and at 2 weeks (i think) a male horomone turns the brain male

isint the male lactation unnatural… and i think that is what he was trying to say.

Found this article mentioned in an NYtimes article linked off of slashdot.
I should send it to Jared Diamond…

I’ve got an even better answer.

Because they do. That’s why.

I guess what I’m trying to say is that we tend to forget that evolution is not an intelligent force. Occasionally a gene mutates and if that gene is passed on at a higher rate than the gene it replaced, then it will become more common. (Like I need to tell you that.)

I suppose it is possible for a neutral gene to arise. (One that neither improves or damages the survival rate of the organism) Then I guess it would just float along the gene pool until some change occurred that either made it preferred or not preferred. I would guess that lactation probably developed in this way.

It’s quite hard to imagine that all of the mechanisms would have evolved at once. It’s even harder to imagine that the random mechanisms of evolution would have, by chance, “figured out” that the organs only belonged in the half of the species with the hormones to activate them.

Of course, one way to know exactly how it occured would be to happen across frozen specimens from every stage of mammalian evolution with the soft tissue intact so that we can examine every stage of the evolution of the mammalian breast. Then we would know which of the mechanisms evolved first.

Maybe some species of pre-mammal were hermaphrodites. Since we are hermaphrodites embryologically, it isn’t hard to imagine that we eventually developed differentiation of sexes. Who knows. But I doubt we could tell much of this from looking at bones.

Enough of the silly theories though. The point I’m making is that WHY things evolved the way they did is simply because it happened that way, and it worked, and it stuck. Evolution didn’t LOOK for a solution to a problem. It just stumbled onto something that was better than before.

I found your conversation very interesting about the lack of the ability to produce milk in mamal male. but befor you get to convenced that it cant be done you might want to read the article that i found on the subject. it can be found at I hope that you find it as interesting as i did

Hi l_katana, welcome to the SDMB, etc.
The link you posted is the same as the one I gave two posts above. There isn’t much discussion in this thread, but I don’t think anyone is at the moment arguing it can’t occur.

Your answers are all correct and you are brilliant geniuses. Now if you would turn your penetrating gazes on a related question about which I could not find a thread on SDMB:

Do human (and all mammal) fetuses (feti?) have several rows of nipples at one point? And then, do they all fade away except the ones that particular mammal needs? Any good facts and/or links on the subject would be appreciated. Also, any good creationist excuses on the subject would be nice. (That’s my interest, you see. I’m not quite that much of a deve.)

Thanks so much! You may now return to your regularly scheduled blatherings.

The short answer is, no. I don’t know about ALL other animals, but I do know lots about guinea pigs, as it happens. Guinea pigs, once born, have only two nipples, like humans. And fetal guinea pigs also have only two nipples. Guinea pig fetuses have been dissected a lot more often than human fetuses, both because there’s a lot less religious/moral squeamishness about guinea pigs than about humans, and because guinea pigs are used as test animals so much. (Why that is so, is a separate lecture, available on request.)

And, it’s not because guinea pigs only NEED two nipples; guinea pig litters average 4, and the babies take turns nursing, standing up (think of very small cows). Most mammals that have only one baby per litter almost always (whch includes humans and almost all the large herbivores) have more than one nipple - cows usually have only one baby at a time and they have 4. The number of nipples is not a function only of average number of babies, but also of maturity of babies at birth, speed of growth,* overlap of mating seasons*, etc. Many reasons to have redundant nipples, but also many reasons why a species, such as guinea pigs, continue quite successfully with “too few” nipples. Species with altricial babies need redundant nipples; species with precocial babies have less need of redundant nipples, but may not lose the extras if they don’t get in the way of reproduction.

Remember, that’s the basic gist of evolution: if something is there, but doesn’t get in the way of reproducing, then it probably won’t be eliminated. If it does get in the way of reproducing, it will get eliminated. So completely useless things can hang around quite easily.