Nudity and Human Nature

From the early to mid-twentieth century, many “progressive” Americans and Europeans believed that nudity was natural, and any shame we had about nudity was caused by Victorian sexual repression. Some people called themselves “naturists” and vacationed in nudist camps. Many others occasionally swam nude with groups of friends or walked around their own homes nude. They expected that public nudity would become common, once society's Puritanical shame about sex disappeared.

Yet our society today is far from Puritanical, and public nudity is still uncommon.

Today, we know enough about evolutionary psychology to see why public nudity is unnatural - why humans evolved feelings of sexual modesty. We can reconstruct the long history of human shame about nudity by looking at the pattern of hair on the human body.

Other mammals must be covered with enough fur to keep them warm in the coldest environments that they live in. When the ancestors of humans began to use animal skins as clothing, they no longer needed fur to keep themselves warm. They were more likely to survive if they lost the fur, so their bodies could cool themselves more efficiently in hot weather or when they were running to hunt or escape predators. They did not need the fur to keep warm in cold weather and when they slept, because they could wrap themselves in animal skins.

Yet there are a few places on our bodies where humans did not lose their fur.

We kept the hair on our head for an obvious reason: you cannot wrap your head completely with an animal skin, so hair was still necessary to keep the head warm, particularly when you slept. Men were more exposed to the cold than women, because they went out hunting, while women kept the home fires burning. As a result, men retained hair on much of their face as well as on the top of their heads, and did not lose their bodily hair as completely as women did. They did not need this extra hair when they were boys and stayed with their mothers, but when they became adolescents and began to go hunting with the men, they grew beards and more body hair.

We also kept our underarm hair for an obvious reason. Our underarms are rarely exposed to the air, so you generally would cool off just as well with or without underarm hair. There was not any survival benefit to losing underarm hair.

But what is the reason that we kept our pubic hair? Unlike the head, this is a part of the body that is easy to wrap in animal skins, so there is no need for this hair to keep us warm. Unlike the underarms, this is a part of the body that is exposed to the air when we are not wearing anything, so losing this hair should have helped our ancestors to cool off, just as much as losing any other fur.

The only plausible explanation for pubic hair is that, shortly after they began using animal skins to keep warm and before they lost their fur, our hominid ancestors developed a sense of sexual modesty that made them keep their genitals covered. Even when they did not need to keep warm, they wore something like Adam and Eve’s fig leaves to cover their genitals. As a result, there was no evolutionary benefit to losing their pubic hair, any more than there was an evolutionary benefit to losing their underarm hair. Like the underarms, the pubic area was not exposed to the air, so they would cool off just as well with or without pubic hair. There was not any survival benefit to losing pubic hair.

Why would our ancestors develop a sense of sexual modesty that made them keep their genitals covered? Evolutionary theory provides an obvious answer: to avoid attracting people who already have mates, which would make those mates jealous and potentially violent.

Animals that pair-bond with their mates because the male helps to provide for the children, including most birds and some mammals, generally isolate themselves from the rest of the species during the mating season. Males are at an evolutionary disadvantage if other males impregnate their mate, because they have to make an effort to help provide for someone else's children. Females are at an evolutionary disadvantage if their mates are attracted by other females, because their mates might abandon them and their children, leaving the children with less of a chance of surviving. As a result, both males and females chase possible rivals away from their territory during mating season: You can sometimes see birds dive-bombing possible rivals to threaten them and drive them away from their nests.

But early humans lived in groups, and they did not have a specific mating season. A couple could not isolate themselves.

Though chimpanzees do not pair-bond, they give us some idea of the potential for violence among animals that live in groups. When a female goes into heat, males threaten or attack other males to drive them away from the female, in order to increase their own potential for mating successfully. The violence is sometimes fatal.

There was even more cause for violence among early humans. They pair-bonded, so females were jealous and possessive as well as males. They did not have a specific period of heat, so the potential for violence was always there. Hominids must have threatened and attacked potential rivals, just as birds threaten and attack potential rivals - but the difference is that hominids could not drive the rivals out of their territory, because they lived in groups. There must have been constant threats of violence from jealous mates.

There was a way to reduce the threat of violence: cover up your genitals so you were less likely to sexually attract someone else's mate. If you had a feeling of shame about showing your genitals, which made you keep them covered, you were less likely to be attacked by a jealous mate, so you were more likely to survive. As a result, evolution hard-wired that feeling of shame into the species.

Thus, the feelings of sexual modesty that we still have today evolved among our pre-human ancestors. They were ashamed to have any member of the opposite sex except their mates see their genitals, because these feelings of modesty helped them to avoid violence.

Because we still have pubic hair, these feelings of modesty must have developed before hominids lost their fur, which means it must date back at least to the early days of Homo erectus, almost 2 million years ago. Sexual modesty has existed among our ancestors for roughly ten times as long as our own species has existed. Sexual modesty has been part of human nature for as long as there have been Homo sapiens, and it has been part of hominid nature for much longer.

It is easy to see why "naturists" began to believe a century ago that shame about nakedness was just a result of Puritanical sexual repression. Victorians were so sexually repressed that respectable women were ashamed to show their legs, and men got excited if they saw "a well-turned ankle." Early in the twentieth century, as this repression began to ease, it seemed plausible that any shame about exposing one's body was just a result of sexual repression.

Today, we should know better. We should be able to see that the "naturists" missed an important aspect of human nature.