or FiOs B)
Boobs help arouse a male and feed the female's young.
The scientific theory on why women have boobs is due to the fact that when we learned to walk upright, there was nothing on the front to mimic the ass which was a prominent feature for attraction in males. So they grew boobs to imitate the ass on the front and now a woman could be attractive to the male species on both sides.
short short version: Boobs mimic the ass because we all are ass men deep down.