What is kissing? A “flame licking» as Victor Hugo described it? “Un earthquake » as the British poet Lord Byron mentioned? Goethe spoke of a “glass of wine» intoxicating, Maupassant of «the safest way to say everything while remaining silent“. Edmond Rostand’s Cyrano de Bergerac described him as “an oath made a little more closely, a more precise promise, a confession that wants to be confirmed“.
Whether in poetry, painting or cinema, the kiss is everywhere, a symbol of love, of passion between two beings. The first trace of a romantic kiss dates back around 4,500 years, in Mesopotamia, where ancient cuneiform texts engraved on clay tablets bear witness to this very particular exchange of fluids.
But kissing wasn’t always just a romantic gesture. In ancient Rome, it was a true tradition, full of meaning. Kissing expressed‘belonging to the same social class: the Romans only kissed among equals. In the Middle Ages, the kiss could seal bonds of commitment and was a sign of recognition between Christians. Among certain peoples of sub-Saharan Africa, Asia and even Polynesia, kissing is a completely strange practice; it is only present in 46% of human cultures. So would it be just that? An essentially cultural event?
A new study relayed by the media New Scientist highlights a new dimension of kissing which goes against this theory: kissing on the mouth would also have a biological function. Research by Matilda Brindle of the University of Oxford has revealed that Neanderthals probably kissed too, suggesting that kissing may be an archaic, ancient, and possibly useful phenomenon. Okay, but for what?
The kiss: an evolutionary paradox
To trace the evolutionary history of kissing, the British team used a statistical method to estimate the probability that certain characteristics existed in ancient species. Simulations repeated millions of times were carried out to simulate different evolutionary scenarios. The results pointed to probable kissing among early humans like Neanderthals.
Research has previously indicated that Homo sapiens and Neanderthals had a similar oral microbiome and that many humans around the world today carry some Neanderthal DNA. This could suggest that they kissed each other, as bonobos, orangutans and other great apes do today. Kissing could, however, be unfavorable to the survival of prehistoric men, by facilitating the transmission of pathogens. Why then did the first men practice this sometimes risky gesture?
Scientists have two hypotheses. First of all, kissing could improve the chances of reproduction – and therefore survival of the species – by making it possible to assess the health of a partner. For example, bad breath would be a sign of poor oral hygiene and therefore an indicator of poor health. The practice could also promote mating by stimulating arousal, accelerating ejaculation and modifying vaginal pH to better accommodate sperm.
Non-sexual kissing would strengthen bonds and reduce social tensions. It would have a so-called “affiliative” function, that is to say a gesture which serves to create, strengthen or maintain social links between individuals. Researchers confirm that among chimpanzees, kissing plays an important role in repairing social relationships. “Chimpanzees will literally kiss and make up after an argument» explains Brindle.
So, is kissing an evolutionary behavior or a purely cultural manifestation? There is no definitive answer. While research shows that kissing has evolved, several scientists say that it is primarily a cultural element, absent in many communities around the world.
