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Hairless Skin and Romantic Love: The Naked Love Theory

By guest contributor Dr. James Giles

A striking feature of human beings is our lack of a thick coat of body hair. Since all other primates have such fur this suggests the primate ancestors of human beings likewise had fur and that, for some evolutionary reason, lost their body hair. But what could this reason be? There are various theories but none is fully adequate.

In a new attempt to explain this loss of body hair I argue that human hairlessness had its origin in the ancestral mother-infant relationship. In the “naked love theory”, as I call it, this hairlessness is ultimately the result of bipedalism or the ability to walk on two feet. Because of bipedalism, ancestral infants lost the ability to grasp the mother’s fur with their feet, as do other primate infants. They thus could no longer hold onto the mother themselves. Early bipedal mothers therefore had to adapt to the new and difficult task of carrying their infants. 

Therefore, infants survived only if mothers had a strong desire to hold them. Because of the pleasure of skin-to-skin contact, the desire to hold the infant would have been stronger in less hair-covered mothers who passed their hairlessness onto their infants. Survival of these infants would have then been greater than that of hair-covered infants.

The hairlessness that began to appear in this context of maternal selection was then reinforced by sexual selection in the male-female sexual relationship. This is because a hairless sexual partner would have enabled the hairless individual to recreate the pleasure of skin-to-skin contact experienced in the mother–infant relationship. Thus, individuals with less body hair were seen to be more sexually attractive than hair-covered individuals. This would have also worked to give hairless individuals a higher chance of leaving more offspring.

One of the benefits of the naked love theory is that, because it explains the origins of hairlessness in terms of the desires for caressing and sex—desires which are fundamental to romantic love—it gives insight into the evolutionary origins of romantic love. This is because the evolution of human naked skin was a precondition for the eventual appearance of romantic love. Comparing aspects of human sexuality with non-human primate sexuality supports this view.

First, although there is a massive involvement of skin-to-skin contact in human sexual intercourse, this is not true for non-human primates. This is simply because the other primates are covered in fur. Consequently, sexual intercourse for them cannot involve skin-to-skin contact in the extensive way that it does for human beings. That is, it cannot involve the caressing of naked arms, abdomen, and thighs, and the rubbing together of naked bodies. Further, when sexual intercourse in our closest primate relatives is compared with human sexual intercourse, not only is it limited in terms of skin-to-skin contact but also in terms of duration. Thus, in the chimpanzee, sexual intercourse lasts for about seven seconds.1 With human beings there is a wide variation. Ten minutes, however, seems to be the average.2

Why then is there this vast difference in the duration of sexual intercourse? The obvious answer, I would argue, is because of the loss of body hair. For it was only with the loss of human hair on the body that sexual intercourse could involve the amount of skin-to-skin contact that it does. Skin-to-skin contact was something that was experienced as highly pleasurable in itself. It therefore became engaged in for its own sake and thus was extended in order to prolong the experience. It is understandable that individuals who engaged in extensive caressing and embracing in sexual intercourse could easily develop persisting attachments to each other. And it is here that we can discern the evolutionary beginnings of human romantic love. For romantic love is an intense attachment to another individual that incorporates sexual desire, a desire that is composed of the more basic desires for mutual baring and caressing. In other words, for me to desire another person sexually I must desire that she be bare or naked for my caress while at the same time desiring that I be naked so that she may caress me. Sexual desire can of course aim at very specific forms of baring and caressing, but these are merely personal expressions of the more basic desire for mutual baring and caressing. The intensity of these physical desires is such that they can easily lead to desires for mutual psychological or emotional vulnerability and care, desires that, according to the vulnerability and care theory of love, lie at the core of romantic love.3

Editor's note: You can read more about Dr. Giles' work in his book The Nature of Sexual Desire, or check out an interview with him here.

Interested in learning more about relationships? Click here for other topics on Science of Relationships. Like us on Facebook to get our articles delivered directly to your NewsFeed.

1De Waal, F. (1995). Bonobo sex and society: The behaviour of a close relative challanges assumptions about male supremacy in human evolution, Scientific American, 272 (3), 82-88.

2Hunt M. (1974). Sexual Behavior in the 1970s. Chicago, Illinois: Playboy Press.

3Giles, J. (2008). The Nature of Sexual Desire. Lanham, Maryland: University Press of America. 

Dr. James Giles - Lecturer in the University of Cambridge, Institute for Continuing Education
Ph.D., University of Edinburgh 

James has a wide range of research interests, including sexual desire, sexual attraction, and romantic love. He is the originator of the Vulnerability and Care Theory of Love, a view that has been presented by Dr Ruth as one of the three most important theories of love. According to his account, sexual desire, which is integral to romantic love, is neither a social construction nor a biological drive. Rather, it is an existential need based on the universal experience of the incompleteness of gender. His research has been featured in several Canadian, Australian, and US newspapers,  including The Wall Street Journal. He has been interviewed in such places as NatureMen's Health, KUAM-TV, and ABC Radio National.

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Reader Comments (2)

Interesting and reasonable hypothesis.

It isn't mentioned that in fact humans are covered with very fine hair, and this is an important aspect of the touch experience.

Hairlessness would also enhance the possibility of arousal by viewing sexual organs or erogenous zones such as breasts, although this aspect would not explain the retention of pubic hair. There may be a different function for pubic and underarm hair, however, such as increasing area for release of chemical attractants.

Perhaps it's too recent and cultural of an adaptation, but the practice of wearing clothing doesn't seem consistent with this theory. Then there's the problem of sunburn and of temperature regulation in general (the reason for retention of head hair?).

May 8, 2012 | Unregistered CommenterArgentcedar

I appreciate these comments and will here try to answer them. I should first say, however, that replies to many of the obvious questions concerning the naked love theory can be found in my article “Naked love: the evolution of human hairlessness” published in the journal Biological Theory, 2011.

The question of why human beings have retained very fine body hair and whether it evolved as important role in touch is a question with no clear answer. Some people have tried to argue that these body hairs play a role in detection of external parasites or biting insects. The problem with this answer is it does not explain why men should have more such body hairs, especially coarser hairs than women. It seems unlikely that men are in more need of insect detection than women. Remaining body hair might rather be simply the remnant of earlier times when we were covered with fur. In this way remaining human body hair would be much like the vestigal leg bones that can be found in snakes: something that serves little evolutionary purpose but indicates an earlier evolutionary state (in the course of evolution snakes lost their legs, just like in course of evolution we lost our fur). I have discussed the issue of remaining body hair more fully in “Why do women have less body hair than men?”, The Conversation, 15 December 2011.

Pubic hair, however, appears to have a different evolutionary history than other body hair. This is indicated by the fact that no other primates have pubic hair. Consequently, it is probable that the primate ancestors of human beings likewise had no pubic hair. If this is true, then pubic hair seems to be a specifically human adaptation. But why should human beings have pubic hair while other primates do not? The answer, I would argue, has to do with our upright posture. For one of the striking facts about pubic hair is that it brings visual attention to the genitals. But it can only do this for a primate who walks upright. For an animal that goes about on all fours or knuckle walks, pubic hair would hardly be visable and thus serve little purpose (which is why other primates never evolved pubic hair). It might also play a minor role retaining sexual scents, but this seems secondary to the visual role. But what evolutionary benefit is served in bringing attention to the genitals? Obviously it serves to stimulate sexual desire and to draw individuals into having sexual intercourse, which in turn leads to reproduction. This is why pubic hair only appears with sexual maturity; for only with sexual maturity can reproduction take place.

Note, however, that male and female pubic hair draws attention to the genitals in different ways. Male pubic hair tends to frame and display the genitals while female pubic hair tends to hide and obscure the genitals. In this way, female pubic hair seems to serve the same function as revealing female clothing, namely, it draws attention to a part of the body by minimally concealing it. The fashion of female pubic-hair removal can in this sense be seen as merely part of the fashion for female clothing to become more and more revealing. For with the removal of pubic hair a female’s genitals are even more revealed (though only, of course, to those who see her naked). Further, like female leg-hair and underarm-hair removal, it serves to exaggerate femaleness by making the female body even more hairless.

Underarm hair seems to have evolved to serve a variety of puposes. Most likely it is an adaptation to trap bodily scents, scents that have a variety of functions. Thus, an infant can recognize the underarm scents of its mother and feeds better when these scents are present. Also, when constantly exposed to male underarm scents, women with abnormally long or short menstrual cycles will tend to have their cycles adjusted to the more normal 28-day cycle. Further, when exposed to each other’s underarm scents, both males and females tend to experience increases in various hormone levels, and thus in physiological arousal (for an account of how hormones might affect sexual desire, see my “Sex hormones and sexual desire”, Journal for the Theory of Social Behaviour, 2008).

Long head hair is most likely, as I have argued elsewhere, a result of sexual selection. That is, it evolved as a feature adapted to stimulate sexual attraction. Further, it seems to be a female trait that was passed on to males, but serves little pupose in the male (much like male nipples). This is further suggested by prevalence of male hair-loss, something that is rare in females. Male hair-loss is also evidence against that idea that head hair evolved to protect us from the sun. If this was its evolutionary function, why should hair-loss be so prevalent? Also, why should hair have grown especially on the head to serve this function, but not on the rest of the body? The shoulders, chest, face, and so on are also exposed to the sun. The answer, it would seem, is because what protected human beings from the sun in Africa (which is where we evolved) was not hair, but rather dark-pigmented skin.

As for the point about clothing, I don’t feel this is inconsistent with the naked love theory. As mentioned, clothing is a recent human invention, appearing somewhere between 72,000 and 42,000 years ago. The evolutionary processes I am discussing took place at least a million years prior to our wearing clothes.

June 22, 2012 | Unregistered CommenterJames Giles
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