What's Up Docs? Doctors' Notes: Kissing
Feb 10, 2026
Dr Matilda Brindle, an evolutionary biologist at Oxford who studies sexual and affiliative behaviours, explains why kissing appears across species. She describes surprising animal examples, explains how comparative and phylogenetic methods trace kissing back millions of years, and discusses intriguing evidence for kissing in Neanderthals. The conversation highlights gaps in research and why broader data would matter.
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How Comparative Analysis Reconstructs Behaviour
- Comparative analysis pairs observed behaviours with a phylogenetic tree to infer ancestral traits.
- This method lets researchers estimate when kissing likely existed in ape ancestors.
Ancient Ape Ancestor Probably Kissed
- Kissing in the common ancestor of large apes dates to roughly 21.5–16.9 million years ago.
- That ancestor likely engaged in behaviours analogous to modern ape kissing.
Convergence Could Explain Distant Kissing
- Similar behaviours in distant species (e.g., bears) may reflect convergence rather than shared ancestry.
- More data across intermediate species are needed to test deep evolutionary claims.