So I got a call the other day to talk to a TV reporter about kissing. Valentine’s Day was coming up, and since it was also Darwin’s Birthday, it seemed fitting to talk about the evolution of this rather odd behavior. Moreover, even though my research focuses more on fighting and war than love and kisses, spending the last year living in France had me thinking about cultural variation in kissing.

People kiss a lot in France. Friends kiss each other when saying hello and when saying goodbye. Boys kiss girls, girls kiss girls, and boys kiss boys.  All this intimacy can make a shy person raised in the Upper Midwest feel quite awkward. And it presents all sorts of challenges. How well do you need to know someone before you kiss them? Do you actually touch the lips to the cheek, or just brush cheeks and kiss the air in their general direction? (Turns out its the latter.)

Though all this kissing might suggest an easy intimacy, in other ways the French are even more reserved than Americans. As French language and lifestyle expert Géraldine Lepère says, “Do not try to hug a French person. They will freeze.”

Adding to the challenge is that the number of kisses expected varies from region to region across France. In our area, Languedoc-Roussillon, three kisses were the norm.  But in other parts of France, the norm involves anywhere from one to five kisses. Greeting friends from those other regions was always a challenge. How many times do we kiss?

Geography of French kissing.
Geography of French kissing.









Thinking about all this cultural variation in greeting kisses made me wonder about the romantic kiss. Is it a human universal, or does romantic kissing show the sort of cultural variability that we see in greeting kisses? And what about kissing in our primate cousins?

Chimpanzees don’t have romantic kisses. But then they don’t really have romance. Mating is a quick business that last seven seconds or so, and the typical mating posture doesn’t bring the lips into close proximity. Females often scream and dart away after than mating rather than staying close to kiss and cuddle (though sometimes males do a bit of grooming of their partner in the afterglow).

Chimpanzees do kiss in other contexts, though, such as greeting and reassurance. Once at Lincoln Park Zoo in Chicago I saw two female chimpanzees engaged in a leisurely lip kiss that lasted at least ten minutes. But I don’t recall seeing anything like that in the wild.

Bonobos are reported to kiss more often, and to use their tongues when kissing. Frans de Waal writes, “French-kissing’ is totally absent in the chimpanzee, which engages in rather platonic kisses. This explains why a new zookeeper familiar with chimpanzees once accepted a kiss from a male bonobo. Was he taken aback when he suddenly felt the ape’s tongue in his mouth!” (de Waal, 1998: p. 103)

Unlike chimpanzees, bonobos frequently mate face to face, which would make romantic kissing more feasible. So perhaps romantic kissing in humans has something to do with our more bonobo-like mating postures.

In The Naked Ape, Desmond Morris suggested that kissing came from sharing food between mother and offspring. This is a classic example of ethological thinking, in which some puzzling, apparently useless behavior is interpreted as a ritualized version of an older, clearly functional behavior. But I’ve never liked this explanation. Partly I suppose because it’s a bit gross. But also, this isn’t something I’ve seen either people or other primates doing. I have seen human mothers pre-chew food for their children, but they transfer the food with their fingers, not their lips. And apart from Junior High stories about kissing couples sharing their chewing gum, food sharing doesn’t seem to play much role in romantic kissing in humans.

More recently, Evolutionary Psychologists have interpreted romantic kissing as a key component of mate selection in humans. By tasting a potential mate’s lips and saliva, kissers may be able to gain useful information about their health and perhaps even genetic quality and compatibility before taking any chances on actually combining their genetic material. One survey study of American college students found that women, more so than men, are reluctant to have sex with someone they haven’t kissed, and more likely to choose not to have sex with someone if they prove to be a bad kisser (Hughes et al., 2007). This makes sense given the sex differences in parental investment that are typical of mammals. Since women rather than men carry any resulting babies inside their bodies for months and then nurse them once they are born, women have a greater evolutionary interest in making sure they they screen potential mates for genetic quality.

Hughes et al. (2007) thus suggest that kissing is an evolved strategy, and argue that romantic kissing occurs in “over 90 percent of human cultures.” Kissing seems kind of a risky way to assess someone’s health, though. After all, if they turn out to be harboring some nasty infection, sharing their saliva is maybe not the best idea. Why not just a quick sniff of their breath instead?

Moreover, thinking about all the cultural variation in kissing in other contexts made me wonder whether romantic kissing was really so invariable.

Darwin, as usual, is way ahead of us here. In his 1872 book, The Expression of the Emotions in Man and Animals, he wrote that kissing was unknown in many non-European cultures:

We Europeans are so accustomed to kissing as a mark of affection, that it might be thought to be innate in mankind; but this is not the case. Steele was mistaken when he said “Nature was its author, and it began with the first courtship.” Jemmy Button, the Fuegian, told me that this practice was unknown in his land. It is equally unknown with the New Zealanders, Tahitians, Papuans, Australians, Somals of Africa, and the Esquimaux.

Darwin’s observation that romantic kissing is not a human universal is supported by a study that will be published in American Anthropologist later this year (Jankowiak et al., in press). This study examined 88 different cultures from the Human Relations Area Files, and also consulted with people working in various non-Western societies. They found that not only was romantic kissing not a human universal, it was only found in 40% of the cultures they examined. Strikingly, they found that romantic kissing was entirely absent in hunter-gatherers, the people whose societies are widely thought to most closely resemble the conditions in which our species has lived for most of our evolutionary history.

This finding seems to me an excellent example of the importance of good old fashioned Anthropology, in which the goal is to find document and explain human variation across the planet. If our picture of human behavior is based only on the behavior of our most convenient study subjects (e.g., American college students), we will come up with a badly distorted picture of our species.

In cultures with romantic kissing, pressing the lips clearly plays a big role in mate choice.  And the evolutionary logic for women being a bit more interested in the quality of kisses than men seems sound. But because kissing occurs only in a minority of human cultures, sex differences in preference for kissing must result from some more general mechanisms, rather than having evolved as part of a specific mental module for smooching.

Works cited:

Darwin, C. (1872). The expression of the emotions in man and animals. London, Murray.

Hughes, S. M., M. A. Harrison and G. G. Gallup (2007). “Sex differences in romantic kissing among college students: An evolutionary perspective.” Evolutionary Psychology 5(3): 612-631.

Jankowiak, W. R., S. L. Volsche and J. R. Garcia (in press). “Is the Romantic/Sexual Kiss a Near Human Universal?” American Anthropologist.

Morris, D. (1967). The Naked Ape: A Zoologist’s Study of the Human Animal .Jonathan Cape.

de Waal, F. B. M. (1998). Bonobo: The Forgotten Ape, University of California Press.