Chapter 3

Op-ed piece: Why are our sexual patterns so unusual?

Evolution by natural selection is a theory that has been confirmed a million times over. No one could doubt its truth. And yet there are still puzzles. One of the greatest is the sexual patterns of our very own species.

Our closest relatives are the great apes. They have different sexual systems, but they all fit within the framework of evolution by natural selection. The gorillas live in widely separated bands and have a strict harem model. Chimps live in troops with promiscuous mating. Humanomorphs form lifelong pair bonds and jointly provide for their offspring.

We are compelled to have sex as adults. In every other species, sex is its own reward. Some members of every species don’t get partners, but they don’t get sick. In the humanomorphs, the pairings are lifelong, so they can raise their children together and continue their sexual relationship to make more. Our bonds hardly ever last for the entirety of a single childhood. Instead of monogamy, the need for bonds enforces an ever-shifting web of sexual partners, enhanced by the greater pleasure from sex within a bond. Our system does allow pairings that are unrelated to bonding, and that at least makes sense. But adults are pulled apart by the greater pleasure of outside relationships, and men and women alike are typically devoting resources to children who are not their biological offspring.

Scientists have discovered that in all our ape cousins and many other animals, there are sexually transmitted diseases. In our species, there are none.

The mind-melding aspects of bonding are an intriguing subject. We have not detected that in any other animal. There is a plausible benefit to that in evolutionary terms. People can experience a wider variety of perspectives on life, notably how life feels to the opposite sex. Also, it is much harder to keep antisocial secrets, and that may confer a survival benefit within groups.