Are Women Different?
Obviously they are, in a variety of ways, but I am thinking of one—behavior associated with sex and courtship. The traditional pattern, in our society and many others, was for men to make advances and women to accept or reject them. The normal assumption was that most men were happy, given the opportunity, to go to bed with almost any reasonably attractive woman, most women much more selective. Over my lifetime that has changed. Substantial numbers of women, in at least some social circles, seem to have shifted to something more like the male pattern. Which raises an obvious pair of questions. Why did the difference exist and why did it, to at least some degree, disappear?
One obvious explanation is prudential. Women get pregnant, men don't. Hence in a world without reliable contraception, a woman faced a much larger risk from sex than a man and adjusted her behavior accordingly, largely restricting sex to partners who could be expected to help her rear any offspring that resulted. A second possible explanation is social. Both men and women valued long term relationships, men preferred to marry women who had not had sex with other men, and women thus found it prudent to maintain at least the appearance of virginity until they had obtained the necessary commitment from a partner. In both versions, the incentive for the traditional behavior pattern would be amplified by a feedback effect. Promiscuous sex was imprudent, hence openly promiscuous sex signalled a lack of sense and/or self control, making a woman who acted that way less attractive as wife, employee, or in most other roles.
A third possible explanation is biological. The scarce biological input to reproduction is neither egg nor sperm but womb space, and it belongs to women. That put them in a position to be much pickier about their partners than men needed, or had any reason, to be. To put it differently, casual sex was a reproductive win for a male—it cost him nothing and might produce offspring. For a female, limited to producing one child every year or two, it made sense to select the father of that child for the best combination of high quality genes and willingness to help support offspring that she could find. The result was to hardwire different patterns of behavior into males and females.
The first explanation is the one that most readily explains what changed. As reliable contraception became available, the incentive for women to refrain from casual sex disappeared. Women, like men, enjoy sex, so women shifted their behavior to be more like that of men. Over time social expectations adjusted; there was no longer a reputational cost to behavior that was no longer imprudent.
That argument works to some extent, but less clearly, for the second explanation. One implication of the increasing availability of contraception was that women who did not want children and did like sex would be willing to sleep with men without long term guarantees, and their competition would weaken the bargaining position of women following the traditional strategy and so weaken the attraction of that strategy.
The third alternative provides no explanation for the change, since human evolution is too slow to produce significant change over so short a period. But it might be consistent with the change, if we assume that something else explains it—most notably ideological and/or social pressure in the other direction, towards women throwing off the constraints of traditional sex roles.
One rather weak piece of evidence for that reading is my impression that the new behavior pattern has not proved entirely satisfactory. At least, I have read a number of articles by women who had followed it and were now unhappy at the results. I have not come across any similar articles by men lamenting the downsides of male promiscuity, although they might exist.