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Kissing Predates Humans by About 20 Million Years, Oxford Study Finds

Phylogenetic modeling of observed primate mouth-to-mouth contact underpins the claim.

Overview

  • Published in Evolution and Human Behavior, the analysis reconstructs kissing in the common ancestor of great apes roughly 21.5 to 16.9 million years ago.
  • Researchers defined a kiss as non‑aggressive mouth‑to‑mouth contact without food transfer and mapped primate observations onto the evolutionary tree using computational statistics, including millions of model runs.
  • Kissing‑like behavior is reported across many Old World monkeys and in chimpanzees, bonobos, orangutans, and most gorillas, with eastern gorillas noted as an exception.
  • The model infers Neandertals likely engaged in kissing, aligning with studies showing shared oral microbes between Neandertals and modern humans, with one report citing an 84% probability.
  • Authors note limits on observational data beyond large apes, report documentation in about 46% of human cultures, and leave the adaptive function unresolved despite hypotheses on bonding, assessment, or microbiome exchange.