Annals of Exploration: The Discovery of Sex

And how the discovery shaped human society

Most animals and all plants are ignorant of the purpose of sex. That is, when they perform the actions that cause sperm and ova to unite, they aren't thinking that this will produce offspring. For plants this is because they don't think at all. For most animals it follows from their apparent inability to link cause to delayed effect. Animals that mate only once don't get a chance to learn from experience. Salmon, for instance, swim thousands of miles to their spawning grounds, battling swift currents, leaping waterfalls and dodging hungry bears, driven by a compulsion beyond their ken. Their struggles are necessary for the species but opaque to the individuals.

Even nonhuman primates appear to lack what scientists call reproductive consciousness. Presumably our ancestors were similarly ignorant until a moment when an insightful Neanderthal, maybe, noticed that females who had sex sometimes had babies nine months afterward but females who didn't have sex didn't. From this discovery developed a great part of what passes for human civilization.

Every society has rules about who gets to mate with whom. Some of the rules are essentially universal, starting with bans on incest (bans that animals don't have). Other rules are variations on the theme of rich and powerful males getting first pick of females. Sometimes the male picks are forcibly imposed; sometimes societies are organized so that females simply find rich and powerful males attractive.

Competition for females, albeit often hidden by layers of rationalization, goes far toward explaining war, through the celebration of martial prowess; competitive sports, which produce the peacetime equivalent of military heroes; business competition, which makes winners both wealthy and powerful; and any number of other activities where males strive to stand out.

The operation of these rules has often been hard on unfavored members of both sexes. But evolution, whether biological, social or, as in many things human, a combination of the two, doesn't work unless many or most individuals lose. As Mao Zedong said about revolution, so with evolution: It's not a tea party.

The rules all depended on the connection between sex and reproduction. To be sure, kings and caliphs enjoyed the sex with their many wives and concubines. But what they really wanted was children, preferably sons, as the wives of Henry VIII discovered. And they and other males wanted to be sure that the children they were raising were actually their own—hence the elaborate strictures on the sexual activities of females.

Societies thrived when they had more children, who grew up to be workers and warriors. Groups that lacked children of their own sometimes stole children from other groups or stole women and girls to be mothers of children for the stealing group. As a rule, the more children the better. Which meant the more sex the better. Or rather, the more procreative sex the better—hence the common disapproval of homosexuality.

The rules didn't change much over time, until the scientific and industrial revolutions of the eighteenth and nineteenth centuries improved standards of nutrition and health sufficiently that populations began to grow rapidly. For millennia the challenge for societies had been to produce enough children; now for some societies the challenge became to avoid producing too many. No longer was more sex necessarily better; increasingly it seemed to be worse. 

But people still liked sex as much as ever. Another discovery resolved the predicament. In the mid-twentieth century contraception became convenient and reliable. Now people could have sex but avoid having children.

A first result of the disconnect between sex and reproduction was the dramatic lowering of birth rates in most countries. This has led to falling populations in many countries and the possibility of a falling world population during the lifetimes of children alive today.

A second, potential result, is the undermining of the practices and institutions that grew out of efforts to influence procreation. Males will continue to compete, but, without the payoff of more children, competitive instincts will dull. To the considerable extent that war reflects a competitive desire to dominate, wars will become less frequent. (There are other causes of war, so they won't disappear entirely.)

It's already the case that the rich and powerful have fewer children than the poor and put upon, so wealth and power will be less self-reinforcing. And in many countries we are past the point where the life choices of women are dictated by their function as bearers of children. In fact, advances in reproductive technology are turning the tables between the sexes, to where males may be optional before long. 

In many nonhuman species, individuals act as though they understand the link between sex and reproduction. Dominant male lions, seals, elk, peccaries, baboons and gorillas guard their harems against lesser males who might cuckold them. But they do so instinctively, in the service of an outcome they don't foresee.

Humans in the modern era, after the age-old connection between sex and reproduction has been broken, often continue to act as though the connection persists. Boys will be boys; instincts die slowly. But instincts don't live forever if they no longer serve a useful purpose.