Marked differences between male and female used to be supported by solid evidence around the globe. However, such distinctions are now getting blurred in developed countries.

The evolutionary backdrop for our species is that of a mostly pair-bonded primate where males and females shared childcare and provisioning responsibilities. As is true of other socially monogamous species, there was a certain amount of sexual (1). Men had more to gain from extramarital sex because they could father children without helping to raise them, whereas women benefited from having a good man with good . Against this backdrop, men are expected to be a lot more interested in casual sex. What of the evidence?

Are Men Always More Interested in Casual Sex?

As women in developed countries are freer to express themselves sexually, their interest in casual sex increases so that they score significantly higher on questionnaires than men in less developed countries (2). For their part, men become less interested in casual sex and converge with female compatriots. So men are not always more interested in casual sex than women whether we compare between societies, or within societies.

Are Women's Bodies Equally Responsive to Sexual Stimulation?

The fact that used to be consumed exclusively by men created the impression that males of the species are sexually hyper responsive. This encouraged speculation that women, by contrast, must be under responsive. Over several decades, researchers have dispelled this myth in various ways.

During the 1970s, swinging parties were fairly common in California and women evidently received a great deal more pleasure from these events than men. Women experienced more orgasms whereas men quickly got tired out (1). Many women also engaged in sexual relations with other women, something that was unlikely in other contexts.

A decade earlier, the Masters and Johnson report (3) studied extensive changes taking place throughout women's bodies during intercourse, suggesting that, if anything, they experienced sexual pleasure more intensely than men for whom bodily changes were less pervasive. The same impression comes from brain research showing that that no fewer than three sensory maps in the parietal cortex light up in functional MRI images when the genitals are (self) stimulated (4). All three of these sensory maps also react when the nipple is stimulated. This means that the breast doubles as a sexual organ in women (but apparently not in men).

Are Women Equally Interested in Pornography?

The received on this topic was that most women were more interested in sex in the context of an emotional relationship rather than physical gratification for its own sake (1).

Research shows that young women are converging with young men in their sexual psychology, in addition to other traits such as and competitiveness. Indeed, a large fraction of self-described addicts of online pornography are women (about 30 percent, 5).

Do Women Hire Prostitutes?

Wealthy women do pay for romantic interactions with younger, more physically attractive, men. This phenomenon crops up around the globe from Japanese love hotels where affluent women meet male sex workers, to Gambia, in Africa, where middle-aged European women consort with youthful African lovers. In many cases, there is no explicit payment for sexual services, as is true in female prostitution. Instead, women pay for rooms, and meals, and give expensive gifts. This indirect payment for services may not include sex if clients are primarily interested in a rather than physical gratification.

When men set out to sell sex to women, they generally do less well than female prostitutes, possibly because most women believe that they can get sex for free and do not need to pay for it. Nevertheless, researchers find that there is a small group of commercially active gigolos in Holland, for example. These typically have no more than a couple of clients per week. Many specify a minimum engagement of two hours and offer something that is closer to a romantic evening than commercial sex. Not surprisingly, most have a regular job in addition to sex work.

The fact that women are less interested than men in paying for sex is clearly not because they do not enjoy sexual interactions but because they see them as more appropriate in the context of an emotional relationship that is punctured by any commercial transaction.

So differences in sexual psychology may not have disappeared entirely but they are getting paper thin.