Abstract

All primates except human beings have thick coats of body hair. This suggests the primate ancestors of human beings likewise had such body hair and that, for some evolutionary reason, lost their body hair. Various theories have been put forward but none is fully adequate. This article presents the “naked love theory.” This theory locates the origin of human hairlessness in the ancestral mother—infant relationship. In this view, hairlessness is ultimately the adaptive consequence of bipedalism. Because of bipedalism, ancestral infants lost their prehensile feet and thus lost the ability to grasp the mother's fur with their feet, as do other primate infants. Early bipedal mothers were thus under pressure to carry the infant. 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 mothers possessing a hairless mutation that enabled them to give birth to hairless 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 in the mother—infant relationship. This theory then helps to explain the evolutionary origins of romantic love.