Female orgasm (n.) During sexual intercourse, an unfakeable indicator that the male is capable of giving women intense pleasure.
Many scientists have examined the female orgasm and yet found no link between the frequency of orgasms in women, and their sexual success. They have thus concluded that the female orgasm is an accident of evolution. This ignores that there are at least five distinct pathways to orgasm in the female.
There is, of course, a strong link between female orgasms and sexual success in the male. In other words, a man capable of giving such pleasure to his female partners will have more success than a man who is not, other attributes such as wealth, power, and looks being equal.
The female orgasm is a mechanism for sexual selection of the male, and has evolved over the last millions of years as a barrier that males must climb over to convince their partners that they are special. Their speciality is no more or less than their ability to climb over this barrier, backed up by the time and energy that takes.
Over years, the female genome has pushed this barrier higher and higher, a gentle arms race between the genders. We can postulate that males have gotten gentler and more patient since we split off from our ape cousins.
Difficulty with orgasm is, in the female, not a sexual disorder, but a sign of a healthy barrier that excludes all but the highest quality males. Indeed, women who have orgasms easily with any partner can be considered abnormal in this respect.
The evolution of the female orgasm as a sexual selection mechanism can be trivially proven by correlating the ability in males to climb that wall with frequency and diversity of their sexual partners. Second, to eliminate causation in the other sense by asking women to express a preference. Third, to show that this talent is inherited.
The female orgasm can also be considered as part of the "black market" in sexuality. Women are overtly attracted to males for their power and ability as providers. Orgasms play no part in this. Indeed, a woman might prefer a husband who cannot climb that wall, since her garden is not the only one around. However, when a women seeks a lover on the side, especially if she intends (as a significant proportion of women do) to have children with one man while attributing them to another, this talent becomes a paramount selector.
Again, trivially proven by interviewing women: if you were married, would you choose a lover on the basis of their power and wealth, or their ability to give you frequent, deep orgasms.
Social regulation that forbids sex before marriage can be seen as a tactic by which men collude to prevent women pre-selecting them on this basis.