Why We Kiss: A New and Intriguing Theory That Predates Human Life on Earth

The Origins of Kissing

Most of us kiss at some point, whether romantically, with family, friends, or formally. However, the origin of this behavior and how it emerged among humans remain subjects of intense debate among historians and anthropologists. A new theory suggests that the evolutionary loss of body hair could be at the root of this gesture’s origin and how it has evolved over thousands of years of human existence.

Adriano R. Lameira from the University of Warwick, a primatologist turned evolutionary psychologist, presented a hypothesis linking the origin of kissing to the social bonding behaviors of our primate ancestors. According to him, kissing may date back millions of years.

The “Groomer’s Final Kiss” Theory

Though the name sounds a bit dark, the “groomer’s final kiss” theory refers to contact that resembled kissing, which was common among ancient primates. This gesture not only removed parasites but also strengthened social bonds within communities with complex social dynamics. Over time, as Homo sapiens and great apes followed distinct evolutionary paths, this “grooming” practice in humans gradually decreased—until only the kiss remained as a legacy of this behavior.

“The evolution of kissing is best understood by looking at the biology and behavior of great apes, which offer a living reference of human hominid ancestors,” Lameira explains. “Among terrestrial primates, including great apes, the dominant behavior for creating social bonds is grooming.”

The “groomer’s final kiss” hypothesis suggests that mouth-to-mouth kissing emerged when ancestral apes groomed each other simultaneously. However, this behavior is rare among present-day great apes, where grooming is typically one-sided, Lameira explains in the study.

Cultural Variations and Universality of Kissing

A 2015 study analyzed 168 different cultures and found that only 46% practiced romantic kissing. However, it also estimated that around 90% of modern human cultures include some form of kissing in interactions, typically between parents and children, relatives, friends, or as a symbolic gesture in ceremonies and formal exchanges.

Although social norms around kissing vary within and between societies, they all share the function of regulating and containing the strong intimacy kissing appears to convey, Lameira noted. People reserve kissing for certain relationships and specific contexts, which suggests a universal biological meaning that transcends cultures and points to an evolutionary basis older than cultural conventions.

The Mechanics of Kissing and Its Parallels with Grooming

The mechanics of kissing—pressing the lips against a surface and applying light suction—are similar to how terrestrial primates remove parasites from the fur and skin of companions. This time-consuming and intensive grooming may have become unnecessary as humans lost body hair and had less exposure to parasites, but its role as a bonding mechanism may have remained.

“Compared to a typical primate, humans groom each other 89% less than expected, especially for hygienic purposes,” the researcher noted. “This is consistent with the loss of fur during human evolution.”

Communication and Social Cohesion

Alongside the reduction of body hair, Lameira highlighted that the development of human vocalization led to more direct means of communication among individuals, possibly making the kissing ritual less essential for social cohesion. Still, this hypothesis is a source of debate among researchers.

Lameira wrote that most schools of thought believe other behaviors completely replaced the social function of grooming. However, researchers have neither considered nor ruled out the possibility that some form of grooming persists, retaining at least part of its original social functions.

A 2023 study found that lip-to-lip kissing existed in Mesopotamia around 2500 BCE, yet its origins remain largely theoretical, given the difficulty of assessing many ancient human and non-human behaviors.

Read the original article on: New Atlas

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