It is well known that the fathers determine the sex of a baby as they carry both the x and y chromosome. What I don’t understand is why men have nipples. If the combination of chromosomes is evident from the time of conception why does the male fetus go through the effort of developing nipples? Why is the development of a male and female fetus identical until the 14th week?
Thanks.
Just a guess : because the gender differentiating chromosome(s?) do not express themselves until - you said - 14th week and by that time the nipple have already started to form themselves?
Welcome to the SDMB, tabreu.
A link to the column you’re commenting on is appreciated. Providing one can be as simple as pasting the URL into your post, making sure to leave a blank space on either side of it. Like so: http://www.straightdope.com/classics/a1_093.html
Men have nipples because all mammals have nipples. It’s not a sex specific trait.
Mammary glands are, nipples, no.
That, and if you run a tongue across one, it causes the man to make Jerry Lewis noises.
Except that men do have mammary glands, which are just as large as women’s mammary glands. (The bulk of the human female breast is just for looks.)
Post #2 pretty much has it; early development (including the formation of nipples and mammary glands) is more or less the same in both sexes. Not all species of mammals have males who develop mammary glands (mice and rats don’t, for instance), but the majority of mammals do.
JRB
And look we shall! 
Also note that male breasts/mammary glands/nipples are quite capable of further development, given proper hormonal adjustment. Given estrogen, men will develop breasts (a standard thing for M2F transsexuals). Cause their prolactin level to rise (such as with a dopamine inhibitor, such as domperidone), and they’ll lactate.
I would say the bottom line is probably because having nipples has been in no way detrimental to continuing the species. And evolution doesn’t really get rid of things we don’t need, I think, only stuff that is actively harmful or getting in the way of procreating.
I’d also WAG that by having nipples being a non-sex specific trait that it lessens the chances of a female being born without them due to a genetic abnormality.
Does anybody else remember the really mean punchline to this joke from Junior High:
Why do men have nipples?
To prove God hates blind babies.
Me neither.
To hang nipple rings from?
Early pacifiers.
Peace,
mangeorge
I should have known better to whip out and post something I only half remembered.
I feel like a boob.
I feel like a boob. Hahaha! Feel like a boob. Good one.
Get’s pretty hot out there on that ol’ dessert, eh?
So if I take dopmeridone and lactate, will there be any side-effects? How far do you think I can squirt?
Or Jerry Lee Lewis noises, even. It depends on how gentle or rough you are. Goodness, gracious, great balls of fire.
And there was much rejoicing…
A long time ago, one of the lesser-known Saturday Night Live characters said that it had something to do with call waiting and call forwarding.