"Was man descended from woman?"
The answer, of course, is no.
Both men and women have nipples because in early stages of fetal development, an unborn child is effectively sexless. Nipples are present in both males and females; it is only in a later stage of fetal development that testosterone causes sex differentiation in a fetus.
All mammals, male and female, have mammary glands. Male nipples are vestigial; they may perform a small role in sexual stimulation and a small number of men have been able to lactate.
However, they are not fully functional and, because cancer can grow in male or female breast tissue, the tissue can be dangerous."
source - Top 10 Useless Limbs