I read your comment on this issue and thought I could help.
It’s believed now that men have nipples because of the lack of something to kill the tissue.
A gene called SRY, which is usually found on the Y chromosome (the chromosome only males possess, usually), activates around week 7 of development. This gene codes for testosterone, which stimulates the development of male organs, and for Mullerian-inhibiting substance, which destroys tissues that would otherwise become female organs. But at the end of week 7, Mullerian-inhibiting substance ceases to exist and around week 8, nipples from in both females and males. Since there is no gene to inhibit the formation of nipples in males they grow normally like Cecil previously stated.
In week 9 breast tissue develops in females, but in males the mammary cords die and therefore breast tissue is not created. The human body naturally grows blood vessels and nerves to protect and feed the cells of the nipples, useless or not.
Welcome to the SDMB, 40DollarBlueGenes.
A link to the column 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
40DollarBlueGenes, that is one of the best first posts I’ve ever seen. Welcome, and please stick around - I think you’d like it here.
In Cecil’s article, there is this quote:
I have a mole a couple of inches to the right of my belly button, and another on the left side, just below the level of the sternum. When I was around 20 and starting to grow hair on my chest, the hair came in thicker in the areas around my nipples and those two moles, in patches that were about two inches across. You can’t really tell anymore now that it’s filled in more.