Overview
- An Oxford‑led team with UCL and Florida Institute of Technology published the analysis on Nov. 19 in Evolution and Human Behavior.
- Researchers standardized a cross‑species definition as non‑aggressive, intra‑specific mouth‑to‑mouth contact without food transfer.
- Kissing is documented across most large apes and in several Afro‑Eurasian monkeys, based on literature reviews and observational records.
- The Bayesian phylogenetic model, run 10 million times, estimated the behavior originated between roughly 21.5 and 16.9 million years ago and persisted across lineages.
- Authors emphasize limited and uneven data and note kissing is recorded in about 46% of human cultures, calling for more systematic field observations.