Why Do We Have Sex?

Why do you sleep at night? This is seemingly a simple question. But in fact it is a most difficult question, as of yet unanswered by science. Many seemingly simple questions are, on close inspection, not at all easy to answer. One of these—perhaps the most interesting—is why we have sex.

Why do you want sex? The usual answer is, of course, based on the known reproductive function of sex. We want sex because our continued existence as a species depends on it. Children come from sex, one learns. And the thing about the stork is just a story.

But the facts on the ground undermine this assumption. First, people continue to engage in sex long after they have stopped having children. Often, their sex lives actually get better, because there are no more worries about unplanned pregnancy (or, a bit later, about Junior popping up bedside mid-action saying he needs to pee).

Which leads us to the following fact: most sex happening right now around the world is not procreative. On the contrary, most of those getting busy at this moment would be shocked and upset to find that their joyful acrobatics have resulted in pregnancy. An intense interest in sex and eroticism is not necessarily linked to heightened interest in producing offspring. In fact, those interests are often inversely related.

Moreover, many sexual behaviors we commonly engage in, even in the fertile years, are not related to reproduction at all. If sex is for reproduction, how is the mechanism of sexual pleasure organized regarding anal or oral sex? And why are you holding hands with your boyfriend? Children do not come of it. Besides, you also hold hands with your three-year-old niece. What's going on here? And what is reproductive about someone pulling your hair? In fact, why does the business of genital, reproductive pleasure spread to all kinds of remote areas not related to reproduction, such as shoulders (very sexy in the nineteenth century), the neck (sexual attraction in Japanese culture), or breasts (contemporary American obsession)? And if a man has a biological urge to find a good mother for his offspring, why do men routinely differentiate between a ‘sexy’ woman and a ‘motherly’ one, and prefer the former to the latter?

Now you say, “Okay, let’s forget all the biology. Why complicate things? Sex feels good. It is a pleasure. I have sex for fun.” But that argument is unsatisfactory as well. It turns out the desire for physical pleasure is NOT the most important reason for sexual activity.

Research shows that the physical pleasure of genital stimulation is not necessarily an important component in the decision to have sex. Researchers Cindy Meston and David Buss a few years ago asked 400 students about their reasons for engaging in sex. After processing the data and eliminating similar or identical answers, they were left with a list of 237 different reasons for sex, including "I wanted to give him an STD,” "I felt sorry for him", "To punish myself", and "I lost a bet."

The truth is, many people are having sex right now without pleasure or any expectation of it. If it’s pleasure you want, if you desire a nice orgasm, you'll get there faster—and cheaper, with more certainty and less risk of pregnancy and disease—through masturbation. So why are you having sex with your partner? And why, when you do masturbate, are you fantasizing about him (or about someone, anyway)?

It turns out that the deep experience of sexual pleasure depends somehow on the presence, and conduct, of others. A brutal illustration of this principle can be found in prostitution. On its face, prostitution is a cold business—the epitome of (mostly male) selfish pleasure seeking. The customer buys physical sexual release for money, plain and simple. But the customer can give himself an orgasm, for free. So why pay? And why is the customer's enjoyment increased if the prostitute produces the sounds of enjoyment and sexual arousal? If the client's motivation is selfish sexual release, the satisfaction of a biological urge, why does it matter to him if the prostitute is aroused? What excites him about the thought that she is enjoying herself? Fundamental social, interpersonal dynamics are apparently present even here, inside the most alienated transaction.

Noam Shpancer Ph.D.