Quick Take
• Contrary to historical belief, humans are not the only species that kiss; various animals, from turtles to bonobos, use lip-to-lip contact and facial touching to communicate and bond.
• Scientific evidence suggests kissing may have evolved from “premastication” (mothers feeding infants) and serves as a vital biological tool for sensing pheromones and reducing stress.
• While most primates’ “kissing” is a platonic social greeting, bonobos are our only relatives known to engage in deep, passionate kissing similar to humans to resolve conflict and strengthen social ties.
Some people believe that humans are the only species of animals that can kiss. A common 19th-century sentiment often suggested that “Man is the only animal that knows how to kiss.” Science has since proven this wrong. Several species of animals have adaptive behaviors that resemble kissing. Turtles tap their heads, moose brush their noses together, and some bats even use their tongues to initiate courtship. Many primates, including humans, display kissing behaviors.
Do Primates Show Affection?
Many primates enjoy long-term pair bonds and will often group together for protection and social stability. Monkeys and apes are both primates, but they belong to different families. Apes, our closest relatives, have larger and more complex brains than monkeys and tend to live in highly intricate social groups. They are often gregarious and form intense bonds with others.
Mother monkeys often kiss their babies to show their affection.
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Another characteristic that primates and humans share is their ability to show affection. While non-human primates lack the rich oral communication of humans, they use vocalizations, facial expressions, and body language to express themselves. One way many primates display affection is through “allogrooming” — sitting together and cleaning each other’s fur. This physical contact releases endorphins, creating a pleasurable and calm state for the animals.
What Does Kissing Mean to Primates?
In mother-infant relationships, gentle touching and kissing are processed by C-tactile nerve fibers. This type of touch reduces stress and actually promotes neuroplasticity within the infants’ brains, helping to form strong emotional connections. When primate mothers kiss their infants, they are enhancing the infants’ psychological and social development. They are also regulating stress responses (lowering cortisol) in their babies while showing affection.
Scientists believe that this type of affection-related behavior may have evolutionary roots in primates since the sense of touch is one of the first senses to develop before an infant is even born. Kissing allows mothers to get close to their babies and smell them, feel them, and see them up close.
Is Kissing a Pair-Bonding Gesture?
Monkeys often look as though they’re kissing in a passionate way
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In the animal kingdom, most primates don’t appear to kiss for “romance” in the human sense. The pressing of one’s mouth to another’s is usually an affiliative behavior, a way to reduce social tension or offer comfort. Interestingly, research by evolutionary psychologists shows that romantic kissing is not even universal in humans; only about 46% of human cultures studied use lip-to-lip kissing as an expression of romance.
However, there is a primate group aside from humans that does seem to kiss in a romantic manner. The bonobos, a species of ape very similar to chimpanzees, do actually kiss. Not only that, they use their tongues to, as humans say, “French kiss.”
There’s Something About Those Bonobos
Bonobos, who are slightly darker, smaller, and generally more peaceful than chimpanzees, will mate facing each other.
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Bonobos, who are more peaceful than chimpanzees, often mate facing each other, meaning they mate face-to-face. While most monkeys and apes engage in “lip-smacking” behaviors that end in brief lip contact, these are typically considered friendly social interactions. Bonobos are different; they engage in non-reproductive sex and deep tongue kissing to resolve conflicts and reinforce social hierarchies.
Bonobos and chimpanzees both share almost 99% of their DNA with humans. Bonobos are more like humans in their mating and relationships than chimpanzees. They are unlike chimps and humans, though, in that they don’t kill each other or other animals. Sadly, bonobos are endangered and face an extremely high risk of extinction in the near future.
Evolutionary Roots of Kissing
Monkeys may learn kissing behaviors by the affection their mothers give them.
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Many scientists believe kissing evolved from “premastication,” a maternal behavior where mothers chew food for their babies before passing it to them via the mouth. Other scientists believe it is an evolutionary tool that helps females choose partners by sensing pheromones and health markers. Because primates are social creatures with long periods of infant dependency, kissing serves as a vital learned and biological tool for survival and bonding.
