New study traces origin of human kissing to ancestral ape grooming

Scientists speculate kissing was established among human ape ancestors as they started spending considerable time on the ground away from trees, which increased the risk of parasitic infestation.

 Kiss's beginning. Image by pedrosimoes7, licensed under CC BY 2.0 (photo credit: FLICKR)
Kiss's beginning. Image by pedrosimoes7, licensed under CC BY 2.0
(photo credit: FLICKR)

In a new study published in the journal Evolutionary Anthropology, scientists conducted a comprehensive review of existing hypotheses to explore the roots of kissing in humans. The analysis looked at parallels in the animal world of behavior similar in form and function to human kissing. Researchers noticed that the final act of grooming in our hairy ape ancestors involves protruding lips and slight suction to remove debris or parasites.

The kiss has been a versatile way by which humans across civilizations and societies have shown affection, intimacy, or social bonding. Kissing is most often regulated by cultural conventions. How exactly humans began communicating affection through kissing remains a topic of debate.

One theory suggests kissing evolved from nurturing care behaviors like premastication, in which caregivers feed infants with pre-chewed food. Another theory relates the act of kissing to have evolved as a kind of compatibility test, in which potential mates tasted and sampled each other orally to determine health.

In their study, the scientists observed that the final act of grooming in our hairy ape ancestors involves protruding lips and slight suction to remove debris or parasites. This act involving protruding lips and slight suction mirrors the context and function of modern human kissing, which evolved from mouth-to-mouth contact among human ancestors after grooming.

"Great ape social behavior suggests that kissing is likely the conserved final mouth-contact stage of a grooming bout when the groomer sucks with protruded lips the fur or skin of the groomed to latch on debris or a parasite," researchers wrote, according to The Independent.

While humans evolved to have less body hair, this final act, which scientists call the "groomer's final kiss," may have remained without its hygienic relevance as a "vestigial action," scientists say. "What was once a time- and labor-intensive ritual to cement and strengthen close social ties became gradually compressed until a groomer's final kiss turned into a crystallized symbol of trust and affiliation," they say.

With this theory, scientists speculate kissing was established among human ape ancestors as they started spending considerable time on the ground away from trees, which increased the risk of parasitic infestation. This could have come "only after" ancient climate change shifted ecology from forested habitats toward drier and more open landscapes, researchers say.

A study published last year points to Mesopotamia around 4,500 years ago as one of the earliest known places where kissing was a "well-established practice." Thousands of clay tablets recovered from early human cultures that lived between the Euphrates and Tigris rivers in modern-day Iraq and Syria reveal that kissing was considered a part of romantic intimacy during these times. Kissing was recognized as a common interaction in romantic and intimate relationships in early human cultures.

Professor Adriano R. Lameira from the University of Warwick presents findings suggesting that kissing evolved from a simple survival action: removing parasites, with the earliest origins traced back 4,500 years to the Middle East.

How exactly humans began communicating affection through kissing remains a topic of debate. Kissing is most often regulated by cultural conventions. The kiss has been a versatile way by which humans across civilizations and societies have shown affection, intimacy, or social bonding.


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In conclusion, the study suggests that the act of kissing may have evolved from grooming behaviors of our primate ancestors. The researchers propose that what was once a hygienic practice to remove parasites transformed into a social and affectionate gesture among humans. This transformation may have been influenced by changes in environment and social structures.

Sources: Yahoo News, The Independent

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