“Whence the female orgasm? After 40 years of debate evolutionary biologists are no closer to deciding whether it evolved to give women a reproductive boost, or whether it is simply a by-product of male orgasm evolution. The latest attempt to settle the dispute involves quizzing some 10,000 twins and pairs of siblings on their sexual habits.
Some evolutionary biologists reckon the female orgasm is adaptive and possibly influences mate choice, strengthens pair bonds or indirectly helps to suck sperm into the uterus. Others argue that women have orgasms for the same reason that men have nipples – being highly adaptive in one sex, the traits tag along for the ride in the other…” (via New Scientist).