You Must Remember This: A Kiss Is Just an Adaptive Trait
Humans have been kissing each other – for one reason or another – for thousands of years. Evolutionary psychologist Adriano Lameira wants to know why, so he’s been spying on our kissing cousins (other apes) to see if they offer any clues that might reveal the purpose, if any, of a good smooch.
“The evolution of kissing is best understood through the biology and behavior of great apes, who offer living proxies of human's hominid ancestors,” Lameira writes in the journal Evolutionary Anthropology.
There are a couple of problems with this kind of observation. For one, even field primatologists are not above anthropomorphizing what they see in the wild. They might observe a snout-to-snout touch between great apes, for example, and quickly assume the behavior is a “kiss.” Another issue is that most other apes do not really kiss the way we do, with “protruded lips and suction movement.” (Our closest relatives, bonobos, also come closest to approximating a human kiss.)
Nevertheless, some hypotheses on the origins of osculation (kissing) are promising. Maybe kissing evolved from “sniffing,” which all primates – and perhaps all mammals – engage in during social inspections. Or maybe the act of kissing grows out of the way a baby nurses.
Lameira favors a third hypothesis, that kissing is a vestigial behavior leftover from when humans discarded a signature act of all other primates, grooming. Apes engage in this literal nit-picking for hygienic reasons, but it also serves a social function that fosters cooperation and cohesion among the troops. Very often a grooming session is concluded when the groomer uses lips to pick the last nit. Seal it with a kiss, as it were.
Homo sapiens lost the need for mutual grooming when we shed most of our fur, but we retained that “groomer’s final kiss,” as Lameira calls it. “What was once a time- and labor-intensive ritual to cement and strengthen close social ties became gradually compressed until a groomer’s final kiss turned into a crystalised symbol of trust and affiliation.”
Photo credit: University of Warwick
