Saying “goodbye” to the conundrum of leave-taking: a cross-disciplinary review

Leave-taking behaviours habitually occur before separation from social interaction in most human societies. It is thought to be a human universal, providing ritual brackets around interaction. Despite Knapp’s claim that leave-taking can tell us a good deal about human interaction, the topic remains critically overlooked from an evolutionary perspective. Cross-species data on leave-taking would be key to unveiling its evolutionary history and its role in sociality, but studies focusing on non-human species are rare. Here, leave-taking is reviewed using an evolutionary approach, pitting it against its symmetrical counterpart, greeting, and emphasising the lacunae in research on leave-taking. It is argued that leave-taking is overdue for serious, empirical attention regarding the ways in which leave-taking could contribute to understanding social evolution. Finally, methods are outlined to operationalise the study of leave-taking and propose the use of “levels of separation” to allow comparison of human and non-human species and to expand research efforts.