If Freud is correct that civilization arises out of the taming of wild sexual desire, then it is not difficult to speculate that the "End of Men," as writer Hannah Rosin put it, is due in part to their ability to enjoy virtually unlimited sexual transactions for free because of contraception. To put it most starkly: contraception makes sex cheap, but women end up paying for it.

The desire for cheap sex has, of course, historically been driven by men, or to be more precise, by the worst of men. Aristophanes (5th c. B.C.) recognized in his comedy Lysistrata that women retained power because of their ability to control men's access to sex, and modern science suggests that he was correct. The cheapening of sexual transactions that has resulted from widespread contraception amounts to a market correction that favors bad men—men who have no desire to care for a woman or her potential offspring.

The disconnect between the apparent benefit of contraception and the reality can be explained, in part, by what is known as "risk compensation," "risk homeostasis," or "offset hypothesis"—all of which point to a phenomenon that psychologists have studied in varied areas such as the use of seat belts, bicycle helmets, and speed limits. The logic is simple: when people undertake a risky activity with a sense of being protected, they amp up the risk level. Drivers of cars with airbags and antilock brakes aren't any safer than those without those features. People drive more carelessly around bike riders with bicycle helmets than without. And people who use contraception engage in risky sexual practices more frequently than those who don't.

Here is a clue to the "McDonaldization of sex": it seems rational to assert that contraception acts like a safety net in sexual encounters. Yet in the real world, this way of looking at sex is woefully inadequate. In short, it is no longer enough to imagine the effectiveness of contraception by imagining two people having sex. It is imperative to think of the way that populations as a whole behave. And on the whole, populations that use contraception engage in a great deal of risky sex.

Natural sexual behavior is not fundamentally rational, in the sense that it always involves careful forethought and planning. It is rooted in desire and passion which, as Plato once observed, can be like a wild horse that must be tamed by a charioteer of a person's will and harnessed to the tame horse of a person's reason. Moreover, sexual behavior, like much human behavior, is fundamentally mimetic. People take their social cues in matters of sexuality from the people around them in a society. (For a scholarly discussion on this, see the work of the theorist René Girard. Overview here.) Following Freud, when primitive men competed for the sexual favors of women who restricted their access to sex, the men had to compete for women by developing communication patterns and sensitivities to their needs. The resulting dynamic was civilization. Women called the shots, and men became more humane.