Scientists Pinpoint Kissing Origins to Large Apes Over 21 Million Years Ago

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New research reveals that kissing-like behaviors first evolved in the ancestors of large apes between 21.5 and 16.9 million years ago, pushing the timeline deeper into primate history than previously thought. This discovery stems from analyzing mouth-contact patterns across modern and ancient primate lineages. The finding challenges earlier estimates and highlights kissing as a deeply rooted social trait predating humans by tens of millions of years.

Researchers mapped documented non-aggressive mouth-to-mouth contacts onto the primate evolutionary tree to estimate origins. They focused on behaviors involving lip movement without food transfer in great ape relatives.

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The Context

Modern great apes like chimpanzees and bonobos frequently display close oral interactions during bonding. These actions mirror human kissing and appear consistently across surviving large ape species.

Statistical models simulated evolutionary scenarios millions of times for accuracy. Results showed high probability that the common ancestor of large apes engaged in such contact around 21 million years ago.

The behavior carries risks of pathogen exchange through close proximity and saliva. Despite this, it has persisted across generations in primate groups living in tight social units.

Humans inherited and expanded these interactions into romantic and affectionate practices. Kissing became widespread in many cultures though it aids neither foraging nor direct reproduction.

Some biologists view the trait as a way to foster alliances and ease tensions in groups. Others highlight how it endured despite health costs in dense primate communities.

Views remain divided with many finding the ancient roots evidence of innate emotional connections across species. A number appreciate ties to primate heritage while some puzzle over its survival given clear drawbacks.