Kissing may have a surprising new origin, as per a new study!

For some, a kiss is the ultimate expression of love or affection. For others, it’s an instinctive way to greet friends or family. But how did this intimate gesture evolve? A new study has proposed a fascinating theory on the origins of kissing: it may have started with grooming behaviors among our ancient ape ancestors, particularly the social grooming of great apes like chimpanzees and bonobos.

Not just a kiss

Every culture has its own “rules” for kissing. In ancient Rome, kisses had distinct names depending on the context: the osculum was a kiss on the cheek, the basium a non-romantic kiss on the lips, and the savium an erotic kiss. Other types of kisses, such as a kiss on the hand or feet to show respect, have long ceremonial and religious histories.

Today, in parts of Europe, two or even three cheek-to-cheek kisses are a common greeting. In Belgium, it’s typically only one. Travel to Oman, and a handshake might be followed by a quick kiss on the nose. Kissing rituals are remarkably diverse, and it’s clear that kissing is deeply woven into our social fabric. But where did it start?
Interestingly however, kissing isn’t as universal an act as you might expect. A 2015 study looked at 168 cultures and found that less than half engaged in romantic kissing. Many indigenous hunter-gatherer societies avoid kissing altogether and even find it distasteful. In fact, only 46% of the cultures studied practiced any form of romantic kissing.

The “Groomer’s Final Kiss”

The researchers propose that the roots of kissing lie in grooming practices. Great apes are known to groom each other by picking through fur to remove debris or parasites — a gesture that serves to reinforce social bonds within their groups. Lead researcher Adriano R. Lameira’s team suggests that, as early humans lost their body hair, these grooming sessions grew shorter, eventually evolving into a quick peck or “groomer’s final kiss” as a symbol of affection and connection.

According to the study, ancestral grooming would end with a protruding of the lips and slight suction, mirroring the physical form and function of a modern kiss. This vestigial act, they argue, might have evolved as a way to symbolise intimacy, even as its original function faded.

Parallels in the animal world

While chimpanzees and bonobos occasionally engage in behaviors that resemble kissing, it’s tough to find exact parallels in other animal species. Some animals nuzzle or bump noses, but most lack a “true kissing” behavior. One notable exception is capuchin monkeys, who show affection by sticking fingers in each other’s eyes and noses. Such gestures, though wildly different, serve similar bonding functions and show that behaviors conveying affection vary widely across species.

The grooming hypothesis is one of many theories that attempt to explain the origins of kissing. Some researchers believe kissing could have evolved from early nurturing behaviors, such as when caregivers fed infants pre-chewed food. Others suggest it acts as a compatibility test, allowing people to “sniff out” potential mates’ genetic health.
The team hopes future research will delve deeper into primate grooming behaviors to find more clues. They suggest examining grooming patterns in different populations of apes, especially those with varying fur densities, to see how these factors may have influenced the grooming-to-kissing evolution.

While it’s unlikely we’ll ever know the full story behind the evolution of the kiss, one thing is clear: this simple act is more complex and diverse than we might have ever guessed.

The findings of this research have been published in Evolutionary Anthropology: Issues, News, and Reviews and can be accessed here.