The very first kiss was hardly exchanged between two people in love, but between our genetic ancestors about 20 million years ago.
Why did we start kissing? From an evolutionary perspective, word-of-mouth contact has no obvious survival advantage; on the contrary, it can spread diseases. Yet we do it – not only humans, but also chimpanzees, gorillas and orangutans. This strongly suggests that kissing is a legacy from our common origins.
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To find the answer, the researchers from the University of Oxford and the Florida Institute of Technology simulated millions of evolutionary scenarios. Their conclusion? The first non-aggressive mouth contact – without food involvement – occurred between 16.9 and 21.5 million years ago.
“Some argue that sexual kissing helps us assess a partner’s qualities and compatibility. It can also be a foreplay that increases sexual excitement and thus the chance of conception,” says lead author Matily Brindle.
She adds that platonic kisses, such as between family and friends, are believed to strengthen social bonds.
The study, published in Evolution and Human Behavior, combines behavioral observations of primates with evolutionary data to trace the origins of kissing. The researchers also claim that human ancestors kissed Neanderthals, which is supported by common mouth bacteria that were transmitted long after the species separated.
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However, why kissing came about, and why it still exists, remains an open question.
