The Science of Kissing: What Our Lips Are Telling Us

by Sheril Kirshenbaum

  Fisher’s reasoning suggests that whatever the means by which kissing arrived among us, its persistence can be traced to its advancement of key human social and reproductive needs. With each distinct human culture, it’s likely that kissing emerged in part out of instincts rooted in our evolutionary past, but was also influenced by unique social norms among peoples, giving it a very diverse cast in different places.

  And humans aren’t the only ones exchanging saliva and affectionate gestures, or engaging in kissing and kissing-like behaviors. Many other species were licking, nuzzling, caressing, and more, long before we arrived—and in many ways their behaviors parallel ours, and often seem to serve a similar purpose. The next chapter, then, looks to the animal kingdom for “kissing” among the furry, slimy, prickly, and aquatic creatures with whom we share the planet. From them, we find additional proof that however kissing originated, similar behaviors are shared not only among human cultures but across species—strong evidence that, despite all the variability, affectionate nibbling and muzzling may be rooted in our common evolutionary lineage with the rest of life on earth.

  Not All Cues Are Hidden

  In 2007, a team of psychologists from the University of New Mexico published a paper suggesting that even though estrus—what we call “being in heat at peak fertility”—is concealed in humans, men may still be able to detect it on a subconscious level. The researchers came up with an ingenious way of studying this by examining the tips earned by eighteen exotic dancers at gentlemen’s clubs.

  These women recorded the onset of their periods, shift hours, and tip earnings for two months (or some 5,300 lap dances), and the results were intriguing. Dancers earned, on average, $70 per hour when ovulating, $35 per hour while menstruating, and $50 per hour during the weeks in between. Notably, women on birth control pills did not show the earnings peak.

  Although the New Mexico scientists aren’t entirely sure what to make of this result, and the sample size was limited, it suggests that although modern women do not visually display rosy bottoms, estrus in our own species may not go completely unnoticed.

  CHAPTER 2

  Jungle Fever

  In the Democratic Republic of Congo, a feisty young male bonobo named Bandaka lived at Lola ya Bonobo Sanctuary. Like many little boys, he enjoyed bullying the girls, and poor Lodja was frequently his victim. Bandaka would pull at her hair and take her toys away, acting like a brute in the sanctuary nursery. The matriarch of their group didn’t discipline Bandaka for his bad behavior, so things went on like this for quite a while.

  Then in 2006, Bandaka and Lodja were transferred to the adolescent level of the sanctuary. This group’s leader forcefully put Bandaka in his place whenever he misbehaved. After one particularly harsh punishment, he fled to the bushes crying while the other bonobos kept their distance. But just then, the most unlikely friend approached: Vanessa Woods watched on as little Lodja wrapped her old enemy in her arms, comforting him with a gentle kiss. The pair spent the rest of the day together as Bandaka groomed Lodja; friends at last.

  PHOTO: VANESSA WOODS

  Bonobo kiss

  The heartwarming story of Bandaka and Lodja represents a classic case of kissing behavior that demonstrates the way other animals express affection for similar reasons that we do—not surprising when you consider that humans and bonobos share about 98.7 percent of our DNA.

  Bonobos nurse by pouting their lips, much like human infants. Parents have further been observed to kiss-feed their young, and later in life, adults become avid openmouthed kissers. My favorite example from anthropologist Frans de Waal involves a zookeeper who innocently moved to accept a kiss of greeting from a bonobo and was astonished to feel a second tongue in his mouth!

  Just like us, bonobos kiss for a variety of reasons. Known as the most amorous of great apes, they often use sex rather than aggression to resolve conflicts in their female-governed society. They kiss for reassurance, and to firm up their relationships with other members of their community. They have also been observed to kiss after being alarmed or frightened, and often do so to express excitement after there’s been clamor in the community. When it comes to kissing, they’re among nature’s most prolific practitioners: Woods reports seeing bonobos in the Congo kissing and nibbling at each other for up to twelve minutes straight.

  And bonobos are just one group of kissers in the animal kingdom. Charles Dickens couldn’t have been more wrong when he wrote, “Man is the only animal that knows how to kiss.” There are practically as many ways for animals to participate in “kissing” as there are species, and they often do so to express affection, to show submission, to resolve disputes, and more.

  However, a caveat is needed here. Behavioral scientists find it extremely difficult to describe the emotional lives of animals other than ourselves. Because different species may process information and interpret the world in vastly diverse ways, it’s not really possible for a human to “know” what another animal is feeling and thinking in any meaningful sense of the term. So scientists strive to avoid using words like “love” to describe the animal relationships they observe. Instead, they use terms such as “mate preference” or “selective proceptivity” when explaining the way that other species bond or pair off. Similarly, when it comes to kissing-like behaviors among animals, we cannot assume other species are motivated by the same factors that we are. Yet there is no doubt that they engage in countless affectionate or at times aggressive gestures that closely resemble the human kiss.

  Moose and ground squirrels brush noses. Manatees nibble at their partners. Moles rub snouts and turtles tap heads. Porcupines nuzzle noses—one of the few regions of their bodies that lack quills. Voles meet at the face and cats lick one another’s heads. Giraffes “neck” by entwining their long necks together, and elephants explore each other’s bodies with their trunks. There are even many species of bats that use their tongues during courtship.

  These behaviors aren’t perfect analogs for the human kiss, but they can serve a similar purpose by bringing two individuals closely together for courtship, bonding, or conflict. These activities among animals take many forms, but they all involve exchanging sensations of taste, smell, and/or touch, and can serve to define relationships—whether between friends, partners, enemies, family members, or even, in rare cases, members of two separate species.

  In fact, we see so many different creatures engaging in kissing-like behaviors that there is probably an adaptive advantage to it all. The process of evolution is driven by reproduction, which in turn is fostered by closeness between the organisms involved. So whether our fellow animals “kiss” to express joy, contentment, love, passion, or confrontation, it is a socially significant means of connecting with another bonobo, dog, or porcupine. These “kisses” lead to a strengthening of bonds, recognition of status, or an act of self-preservation. In the big picture, all of these activities help to perpetuate the species.

  SO LET’S LOOK MORE closely at some of the most striking and memorable examples of kissing-like behaviors in other species, starting with those most closely related to us and moving out from there.

  Just as for humans and bonobos, kissing relieves tension for many other apes as well. Chimpanzees kiss with open mouths but not with their tongues, and primatologist Jane Goodall has reported that they sometimes pout and touch lips in greeting. As with bonobos, chimp kisses can be elicited for many reasons, especially from excitement over the presence of food.

  Granted, chimpanzees are not able to experience the same sensations that humans enjoy from kissing because their lips are narrower and do not purse outwardly. Accordingly, they don’t kiss in the same contexts that we do; kisses among chimps are probably not a symbol of sexual intimacy, but more an expression of rapport between community members, similar to a human hug. Most observations of chimps kissing involve a quick exchange between females. According to Frans de Waal, kissing among chimps often serves as a way to reestablish bonds and relationships—meaning that humans a
re not the only ones to “kiss and make up” after quarreling with friends and family members.

  But kissing and kissing-like behaviors certainly aren’t confined to great apes. Another obvious example occurs in our best friends: dogs. They do much of their social business by means of sniffing at other dogs—a canine parallel to the sniffing greetings that we see in some human societies. Most readers have also no doubt been licked, sometimes in the strangest of nooks and crannies, by a pet dog. Canines lick each other, their owners, and many other people, places, and things. If it’s a noun, dogs will probably lick it. It’s certainly not a classic “kiss,” and not meant romantically or even necessarily as a show of affection. Instead, licking among dogs is a means of greeting and grooming. It can also reflect recognition of social hierarchy, in which subordinates lick more dominant individuals. So the next time it happens to you, consider it a compliment.

  Dogs aren’t the only lickers; in many animal species, licking is a form of grooming. As animal behaviorist Jonathan Balcombe explains in his book Pleasurable Kingdom, scientists have observed that licking can soothe horses, cows, cats, monkeys, and more. These animals’ coats protect them from parasites and dirt, so it behooves many same-species pairs to spend hours grooming a partner.

  Among mammals, one of the more uncomfortable “kisses” occurs in the elephant seal, a large marine animal that famously features an unusually long and bulbous nose. When an elephant seal wants to mate, he puts his flipper over the side of a female and grips her neck with his teeth. It’s not what we would consider the most romantic encounter, but apparently this works for the species. Lions, too, tend to give what can only be described as a rather aggressive “love bite” during sex.

  PHOTO: NICOLAS DEVOS

  And it’s not just our mammal relatives that give kisses or build bonds through behaviors that seem closely related to our own. Many bird species, for instance, nuzzle beaks affectionately (so do dolphins—a different kind of beak, of course). Such “bill-fondling” can appear similar to mammalian or human kissing, as partners caress each other.

  It’s not surprising that some birds grow so enamored considering that many species, such as parrots and ravens, mate for life. A pair perches side by side, preening and feeding one another. Unlike humans, they can’t compose romantic sonnets, so physical affection may serve to express similar sentiments. What’s more, pet parrots commonly accept owners as their “mates,” and nip tenderly on the lips of their human companion, expressing vulnerability and adoration.

  THERE’S ANOTHER SIDE TO “kissing” across the animal kingdom that’s not particularly pretty but serves a vital purpose and parallels the process of premastication: regurgitation. Ethologist Niko Tinbergen of Oxford University studied the behavior of herring gulls, in which baby birds peck at the conspicuous red spot on a parent’s bright yellow beak as if “kissing” Mom or Dad to be fed. Tinbergen presented chicks with various cardboard gull heads that differed in color, shape, and spot location, hoping to find out exactly what elicited the “kiss” for food. His results revealed that gull chicks are born with a preference for long, yellow objects featuring red spots, providing these young birds with a means of obtaining sustenance right from birth without having to pick up any learning. Regurgitation may sound disgusting, but to baby gulls, getting a parent to spit up is quite literally the “kiss” of life.

  Regurgitation for the feeding of young is found among birds ranging from the ibis to the albatross, but some mammals, like wolves, employ a kissing-like behavior to a similar end. Hungry pups nudge and lick the muzzles of adults to stimulate regurgitation and to eat. It may not sound appetizing, but it’s effective. Other great apes, cats, dogs, and some marine mammals also feed their young through some form of mouth-to-mouth transmission of food.

  And there are still more animal “kissers” out there. A large tropical freshwater fish found in Thailand and Indonesia, called the kissing gourami, touches lips with others, often as a sign of aggression, during feeding, courtship, and fighting. Other species of fish will bite and nudge opponents during combat. Snails, meanwhile, may be the most sensual critters of all, locking together while massaging each other all over.

  Even though we will never be able to fully understand the motivations of other species or how they interpret the world, observations of kissing and closely related behaviors suggest that reducing the explanation to mere strategies for survival and reproduction would be far too limited. Additionally, individual animals often exhibit behaviors unique to themselves, not to be found in other members of their particular community. Some press lips, beaks, muzzles, or snouts, while others may express a similar sentiment through a very different display. So in the examples of animal “kissing” provided already, we must not assume that the behaviors recorded are close to 100 percent representative of an entire species. After all, our encounters of animal “kissing” have of necessity been very limited relative to the abundance of life on the planet.

  Further, describing many of these unusual, funny, and fascinating styles of “kissing” found in the animal kingdom barely scratches the surface of what’s out there, given that scientists estimate there are somewhere between three and thirty million species on earth. What’s clear is that evolution is likely behind all of these behaviors, tying individuals together for a wide variety of important reasons.

  But if the evidence from the animal kingdom—in combination with the evolutionary accounts we’ve surveyed—suggests a deep biological basis for kissing-like behaviors, culture is also a central factor in determining precisely what form a kiss takes at a particular time and place. The next two chapters therefore survey the rich pageant of kissing among European and non-European peoples, starting as far back as we can peer toward the dawn of humanity.

  In the process, we’ll see that humans have gotten pretty good at kissing. Or at least it’s clear that our species has had thousands of years to develop, improve, and spread this behavior in its now dominant mouth-to-mouth form.

  Koko’s Kiss

  Koko, a female lowland gorilla, was born in 1971, and over her life has been the subject of the longest continuous language experiment ever performed upon a member of a species other than our own. Dr. Penny Patterson has taught Koko over one thousand signs; further, she is capable of understanding around two thousand words of spoken English. Among her extensive vocabulary are the sign and vocalization for “kiss.”

  When the time came to find Koko a suitable mate, Dr. Patterson showed her video footage of males in zoos, so she would be able to decide which one she wanted to meet. Gorillas like to choose their own partners, so you might say Koko was “video dating.” According to researchers, Koko would give a thumbs-up or thumbs-down to each individual depending on whether or not she liked what she saw—that is, until the moment when a 400-pound male named Ndume from the Brookfield Zoo outside Chicago appeared on the monitor. Koko pressed her lips directly to his image onscreen—leaving scientists with no question as to whom she preferred.

  CHAPTER 3

  Kiss My Past

  Looking up at the night sky is like peering back into the past. Here on earth, light travels from one point to another so quickly that it’s hard to notice it takes any time at all. But in outer space, distances are so vast that they are measured based on the time period necessary to traverse them. Physicists clock the speed of light at 9,460,730,472,580.8 kilometers per year—very fast, and yet light from the bright stars we see in the night sky still takes a very long time to reach us.

  In July 2009, the Hubble Space Telescope captured this image of NGC 6302, otherwise known as the Butterfly Nebula, 3,800 light-years away in the constellation Scorpius:

  © SPACE TELESCOPE SCIENCE INSTITUTE

  NGC 6302, the Butterfly Nebula

  Perhaps, then, the galaxy’s first “kiss” happened a very long time ago, and was made up of star stuff.

  Back here on earth, the human lip-print has been traced by classicists and anthropologists over a much short
er period—merely a few millennia. The significance of kissing, its popularity, and its numerous modes have varied dramatically over this time, as have the cultural norms and social expectations of those involved. Many ancient kissing styles would sound and look exceedingly strange to us today. And yet these earlier forms of kissing show many commonalities with what we see in other species, and in our present selves.

  If history provides one important lesson with regard to kissing, it’s that this behavior is nearly impossible to suppress. Over thousands of years, the kiss has been derided by poets and commentators as disgusting, venal, dirty, and worse. Popes and emperors repeatedly tried to punish practitioners, citing moral or health-related reasons, yet not even the world’s most powerful men could police the lips of their subjects. We’ll see as much in this chapter as we survey the evidence concerning kissing’s cultural origins, significance, and unusual trajectory throughout the ages.

  ACCORDING TO SCHOLARS of the relevant historical records, kissing as we know it doesn’t seem to make any documented appearance in human societies until around 1500 BC. The earliest and best literary evidence we have for very ancient kissing, according to anthropologist Vaughn Bryant of Texas A&M University, comes from India’s Vedic Sanskrit texts, the foundations of the Hindu religion. They began to be compiled in a written form around thirty-five hundred years ago, having previously been part of an oral tradition.

  In the Vedic texts no word exists for “kiss,” but the same word is employed to mean both “sniff” and “smell,” and also has connotations of “touch.” Thus when the Atharva-Veda describes a curious act of smelling with the mouth, this could refer to an early kind of sniff-kissing. Similarly, a passage from the Rig-Veda uses the word “sniff/smell” to describe “touching the navel of the world”: once again, possibly an ancient kissing reference. Another intriguing line from this text translates to read that a “young lord of the house repeatedly licks the young woman.” Here, “lick” may represent a kind of kiss or caress.