While only females have mammary glands, we all start out in a similar way in the embryo, the authors explain. The embryo follows a female template until about six weeks, when the male sex chromosome kicks in.

Men, however, have already developed nipples.

This was among many questions that ‘you would only ask a Doctor after your Third Martini.’ It came from a book by Dr. Goldberg entitled ‘Why do Men have Nipples?’ More can be found at Yahoo News.