There are all kinds of kisses. They can be tender or passionate. They can be romantic or friendly. They can even be stealthy and stolen. A kiss can change the course of history. But despite its infinite nuances, a new study published in Evolutionary anthropology claims that they all have the same origin: a grooming practice in which chimpanzees and other great apes comb their companions’ fur with their fingers and use their lips to remove debris. Humans, research suggests, have inherited a vestige of this ritual.

How kissing went from a fraternal and hygienic gesture among primates to one of the greatest symbols of communion between humans, explained Adriano R. Lameira, an evolutionary psychologist at the University of Warwick (UK) and author of the article. study for a while. The laboratory he directs is responsible for tracing evolutionary origins of the most particular practices or characteristics of humans, from dance to imagination. Kisses are one of them. “If you think about it, it’s a pretty strange way to show affection. We put our lips together and make random, intuitive sucking gestures,” he explains.

To understand the evolution that preceded modern kissing, Lameira had to dive into the rabbit hole that scientific literature can sometimes be. He was looking for an answer. And he found not one, but several. One of the existing theories proposes that lips evolved to be attractive and that’s why we kiss. Another, that joining lips is a mechanism that some mammals have discovered to feel closely and establish some compatibility. There is also a theory that establishes the origin of kissing in premastication. That is, a primate’s parents chew food and then push it into their offspring’s mouths in a kiss-like gesture. A final hypothesis suggests that kissing is a reflection of breastfeeding. “All of this may be valid, but most of them have difficulty explaining the way kissing is done, the context of its use and its function,” explains the researcher.

The hypotheses were dismantled one by one. Pre-chewing can explain the shape because the lips are pushed outwards, but there is no suction, quite the contrary. Breast-feeding it works a little better in terms of form, but we still need to explain why, in adulthood, this behavior transmutes into a practice on other parts of the body and is no longer linked to food. The smell hypothesis collapses because a hug is more effective at smelling than a kiss. “The only behavior in the great ape repertoire that fulfills the same form, function and context as modern kissing is the final stage of grooming,” says Lameira. In this practice, primates check a partner’s fur for parasites, insects, or debris. When he finds it, the groomer approaches with protruding lips and makes a sucking movement to catch the residue found in his partner’s coat. “Suddenly, I found myself faced with what probably represents the oldest form of kissing,” concludes the researcher.

Over the centuries, humans have evolved to lose their fur. The study suggests that during this period the hygienic function of grooming was lost and the ritual condensed into kissing as we know it today. “We no longer groom each other, but we kiss as a symbol, as if we had done it,” explains Lameira.

Sheril Kirshenbaum, researcher and author of The science of kissingsays that “the hypothesis put forward by the new study is interesting” and could be added to the repertoire of existing conjectures, but it is not definitive because the practice of kissing has experienced several ups and downs throughout the history of humanity. It has appeared and disappeared across the world at various times for various social, emotional, and even anatomical reasons. “With kissing, the good news is that we don’t have to choose just one explanation,” she says. Furthermore, it is not exclusively a human asset. Kirshenbaum points out that “many other animals exhibit kissing-like behaviors that did not start in us.”

The cultural burden

The question that remains to be answered is to what extent this seemingly primitive relic of kissing has been influenced and modified by human cultural development. Kirshenbaum believes the best answer, as is often the case, might lie somewhere in between. “Kissing is an example of behavior where nature and culture complement each other. We seem to have an instinctive drive to connect in this way, but the form and interpretation of a kiss is determined by our upbringing and experiences,” she says. Lameira is more categorical: “To kiss is to associate with cultural development.”

The first kisses were recorded in Mesopotamia 4,500 years ago, according to a published article In Science in 2023. The study compiles Sumerian and Akkadian writings that describe the practice of kissing with a dual function, as part of the sexual act and a display of affection between family and friends. Troels Pank Arbøll, professor at the University of Copenhagen, expert on ancient Middle Eastern civilizations and author of the study, says the following about the study published this month: “The author is trying to prove the credibility of the hypothesis he puts forward. forward, which is good in principle, even if its inclusion and critique of previous research or alternative theories seems superficial.

For the Danish scientist, “it is curious that the article does not take into account recent and relevant research in anthropology, which offers alternative perspectives”. One of them was published in 2015 In American anthropologistwhich points out that there is no evidence that kissing is universal among humans, or even close to universal. Only 46% of the cultures sampled in this research had the romantic kiss among their repertoire of rites and customs.

Many human rituals have been modified, but the kiss remains virtually unchanged. It had other names and protocols, but it prevails. “Evolution doesn’t throw away things that work and doesn’t fix things that aren’t broken,” Lameira ventures.

For kissing to change, something in our way of life would also have to change. And despite this, humans would look for a substitute. This happened during the Covid pandemicwhen kissing became a vector of disease. “We will not succeed in kissing only out of fear or responsibility,” psychiatrist and psychoanalyst Diego Figuera told EL PAÍS at the time. Overtaken by the uncertainty of Covid-19, Figuera dared to say that the kiss could take on a new meaning. “Those who dare to kiss during this time will experience it as an expression of great love for the other. I kiss you and I guess you could infect me,” he said. And the kiss survived.

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