Overview
- The peer-reviewed study, led by University of Oxford researchers with collaborators at Florida Institute of Technology, appears in Evolution and Human Behavior.
- To compare species consistently, the team defined kissing as non-aggressive, mouth-to-mouth contact without food transfer.
- Using trait mapping and Bayesian models run 10 million times, the analysis places the origin between 21.5 and 16.9 million years ago and notes retention in several great apes including chimpanzees, bonobos, and orangutans.
- The reconstruction indicates Neanderthals very likely kissed, a finding consistent with prior evidence of shared oral microbes and interbreeding with Homo sapiens, with some reporting a probability of about 84%.
- The authors stress limits such as sparse data outside great apes, frequent reliance on captive observations, and human cultural variation (kissing documented in ~46% of societies), leaving functional explanations unresolved.