I know the standard answer is because we'd look weird without them, which of course isn't true, if men never had nipples, we wouldn't look funny without them.

But I was wondering if at some point, back in the caveman era (oh yeah, i'm that scientific) if male nipples didn't serve a purpose. I was thinking that if women die during childbirth today with everything we have that can save lives, surely early man (as a species--not sexism) had many moms lost during childbirth. Surly our male ancestors didn't just ignore the baby and let it die...maybe they did, but if he saw his wife breastfeeding and wanted to have children to help him later in life, maybe he was able to breast feed.

I used to argue that the genitals aren't formed until further along in the fetuses life span and therefore nipples were present on every human just because they were there before a fetus became male or female, however, my mother recently obliterated my theory by stating that our sex is determined from the moment of conception. The sperm carries that essential x or y chromosone to determine (among other things) the future baby's sex.