Gerardo Gomez / AFP via Getty ImagesAmong chimpanzees, the act of removing parasites is important in social dynamicsGerardo Gomez / AFP via Getty Images
As well as being a display of affection, the human behavior of kissing, a widespread social custom in many cultures, may originate in good hygiene. This is the theory suggested by Portuguese primatologist and evolutionary psychologist Adriano Lameira, from the University of Warwick, UK, based on observations of our closest cousins, the other great apes (chimpanzees, bonobos, gorillas, and orangutans). According to Lameira, primates that developed terrestrial habits also became more prone to infestations, making the social behavior of picking parasites off each other even more important. The final stage of this grooming habit, after parting the fur to find fleas, lice, or ticks attached to the skin, often involves using the lips and sucking to remove the unwanted guest. When the evolutionary process created naked primates (human beings) this social behavior may have been transformed, giving rise to the kiss: a manifestation of trust and closeness. Do you like it when someone tousles your hair? This feeling may be from the same origin (Evolutionary Anthropology, October 17).
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