Srsly like mystery of the universe over here...

https://m.youtube.com/watch?v=VAZsBEELqPw

I cant tell if this is a joke/spammy thread or a serious question, but anyway I googled it and I found out pretty fast that its because of development in the womb where you could be either a boy or a girl, before the Y chromosome takes over.

http://www.livescience.com/32467-why...e-nipples.html

All the sources I found seem to agree so just read that

Thanks. Now my life is complete.