Naked, Colorful Skin and Its Role in Human Social Interactions
The evolution of mostly naked skin in the human lineage heralded major changes in the biological and social functions of skin. The evolution of enhanced barrier functions of the epidermis made it possible for functionally naked skin to repel water, resist abrasion, and combat harmful microbes and ectoparasites. Naked skin also changed the nature of human social interactions, both at a distance and at close quarters, although many of the details of exactly what happened when are not yet known. With raising of the hackles precluded, displays of fear, anger, and excitement became focused more strongly on facial expressions. With the loss of most body hair, grooming became more focused on scalp hair and the face, and huddling for thermoregulation probably became more important. Erogenous zones and increased sensitivity of facial skin promoted infant-mother and pair bonding. Naked integument almost certainly became a canvas for social expression early in the history of Homo sapiens, if not earlier, and the communication functions of temporarily and permanently decorated skin have only increased over the millennia. As visually oriented primates, humans attend closely to the appearance of skin and make assessments of age, health, and group membership based on it.