Naked love: Here’s a theory about why you aren’t covered in fur
Human beings are the only primates who lack a thick coat of fur. This suggests that the primate ancestors of human beings also had fur and in the course of evolution lost it. Of course we also have body hair, but it is for the most part so fine and short as to be nearly invisible and thus to render us virtually naked. But why should we lose our body hair while all other primates retained theirs?
Although there are numerous theories, none of them seems fully adequate. One of the problems that many of the theories share is they only consider evolution from the perspective of the adult. But infants are also under the pressures of evolution. Looking at the situation of the ancestral infant provides some clues to this puzzle. The answer, I want to argue, is that hairlessness appeared in the context of the ancestral mother-infant relationship by encouraging the maternal desire to hold the infant. It was then reinforced in male-female sexual relations.
To see how this came about, let us start by noting that the driving factor in human evolution seems to be bipedalism or the ability to walk on two legs. Bipedalism had many advantages. However, there were also many costs for this new-found ability. One of the great costs was the loss of feet that could grasp.
This was not a major problem for older individuals since they would have then spent most of their time on the ground. However, it was a problem for infants because tree-dwelling ancestral infants, like all other primates, would have only survived by being able to grasp the fur of their mothers with their hands and feet.
The fact that, like all other primates, our ancestors also grasped their mothers’ fur is suggested by the grasping reflexes that are still present in human infants. If one places a finger in the hand of a newborn it responds by grasping the finger. Or if a newborn’s feet are touched it responds by curling the toes in what looks like a grasping motion. But why should a human infant have such reflexes? A likely answer is they are the vestiges of an ancient reflex to grasp the mother’s fur.
Luckily, however, the infant’s lack of ability to hold onto the mother could be compensated for by the mother’s ability to hold onto the infant. For one of the remarkable advantages of bipedalism is that it frees the arms to carry things.
However, the mother’s ability to hold the infant was only part of what was needed. The other part was the mother’s strong desire to hold the infant. Continually clutching an infant is hard work. One can imagine that many of our early ancestors found the task so daunting that they frequently put the infant down while they did other things, only to have it snatched by a predator or swarmed by insects. Clearly, anything that aided in strengthening the maternal desire to hold the infant would have been selected for. But what factors could have strengthened such a desire?
An answer is the intimacy and warmth of skin-to-skin contact with the infant. Many women report pleasure in such contact, especially in breastfeeding. A large percentage of mothers feel sexually aroused during breastfeeding, with some even reporting orgasms. Also, mothers who breastfeed their infants with naked contact report higher amounts of affectionate love for their infants than do those who breastfeed without such contact. Further, research shows that infants in skin-to-skin contact with their mothers during breastfeeding are more relaxed, cry less, and breastfeed longer that do infants lacking naked contact. Obviously, these are all factors that strengthen the human maternal desire to hold the infant. It seems likely the same would have been true for our bipedal ancestors.
Plainly, however, skin-to-skin contact here is only possible between a hairless mother and a hairless infant. Consequently, naked skin would have been selected for as something that strengthened the ancestral mother’s desire to hold the infant. This evolutionary mechanism, which I call maternal selection, also helps to explain why women are more hairless than men.
Male adult hairlessness, which is less extensive, would probably have evolved through genetic correlation with female hairlessness.
However, in the naked love theory, maternal selection is only one mechanism that selects for hairlessness. The other is sexual selection, that is, the process of an individual choosing a sexual partner on the basis of the individual’s sexual attractiveness. In this view, hairless individuals would have been seen as more sexually attractive than hair-covered individuals ( Sexual selection probably also explains the existence of long female head hair, and of both male and female underarm and pubic hair, which trap sexual scents and draw attention to the genitals. The prevalence of male pattern baldness suggests that male head hair was not selected for but, like male nipples, was merely genetically passed on to males from females).
It seems clear that a baby who enjoyed hairless skin-to-skin contact with his or her mother would seek to recreate such contact as an adult with a hairless sexual partner. This would have especially been the case for ancestral males since the increased female vulnerability with having to carry and tend to infants would have meant that it was the males who were primarily exercising sexual selection.
One of the advantages of the naked love theory is that it helps to explain the evolutionary origins of romantic love. This can be seen by comparing human sexual and attachment behaviours with those of our closest fur-bearing relatives. One of the things that distinguishes us here is the intensity and duration of sexual intercourse. While sexual intercourse for the chimpanzee lasts for a mere seven seconds, for humans it is typically about 10 minutes. That is 85 times longer. One of the reasons for this is the extensive skin-to-skin contact, fondling, and caressing we often use in sexual intercourse. Clearly, this is only possible because of naked skin.
The intimacy and warmth of skin-to-skin contact with an infant likely increased the desire of our ancestors’ mothers to hold and protect their babies.