Overview
- The peer-reviewed study in Evolution and Human Behavior estimates the origin of non-aggressive mouth-to-mouth contact in the great-ape lineage between about 21.5 and 16.9 million years ago.
- Researchers defined a kiss as mouth-to-mouth contact without food transfer to enable consistent coding across species where fossils cannot capture behavior.
- Documented kissing-like behavior in chimpanzees, bonobos, orangutans and some gorillas provided the primary data for the comparative analysis, which was iterated 10 million times.
- The modeling infers Neanderthals probably kissed and makes interspecies kissing with Homo sapiens plausible, aligning with evidence of genetic admixture and shared oral microbiomes.
- Authors emphasize limitations including heavy reliance on captive observations and sparse data beyond great apes, and note that functions may range from mate assessment to bonding and reconciliation, with romantic kissing recorded in about 46% of human cultures.