Waving goodbye: “Leave-taking” isn’t unique to humans

dog with paw in air

A formal end to social interactions may not be a unique trait of humans. Photo credit: Camylla Battani via Unsplash

We have all been in situations where it feels impossible to leave an interaction. When your conversation partner will not let up, it can be challenging to find a gap to call it quits. Yet almost all human interactions end in some sort of goodbye. For example, waving is a common farewell in many European cultures and is used in British and American Sign Language.

…greeting behaviours are found across the Animal Kingdom.

Although “leave-taking” is seemingly a central part of social interactions, it has long been considered a uniquely human trait. This is despite the fact that hellos are found across the Animal Kingdom. For example, female hyenas sniff their respective “pseudo-penises” when saying hello, and baboons have complex greeting rituals that are designed to be attention-grabbing.

Signals intended to end social interactions in nonhuman animals are, however, glaringly understudied. There have been some morally questionable attempts to raise apes “as humans” to assess the affect this has on language learning. In ‘Project Nim’, humans raised a 2-week-old chimpanzee named Nim Chimpsky to adulthood and taught him American Sign Language. Nim never learned to sign ‘goodbye’, but he did frequently sign ‘finish hug’. Perhaps that was his equivalent. Either way, the lack of scientific research in animal leave-taking has pushed the uniqueness narrative that humans are so keen to perpetuate.

…the lack of scientific research in animal leave-taking has pushed the uniqueness narrative that humans are so keen to perpetuate.

Recent observations are forcing us to wave goodbye to this assumption. Research from the University of Oxford has revealed that wild primates take leave from social interactions using specific signals.

Researchers Lucy Baehren and Susana Carvalho compared the behaviours of wild chacma baboons just before finishing “solo” (e.g., foraging alone), “proximate” (e.g., foraging alone but close to a troop-mate), and “social” activities (e.g., grooming a troop-mate). Baboons perform a purposeful reorientation towards the direction of travel before departing from social interactions. This action was only associated with social activities, suggesting its function is to end the activity whilst maintaining social bonds.

That is not to say that all chacma baboons—let alone all baboons—will take leave in this way. Just as there are different ways that humans say farewell, there will likely be regional variation in nonhuman leave-taking.

A 2022 study found that Guinean chimpanzees seem to communicate when leaving social interactions less frequently than when joining them. This is unlikely to hold true for other communities, especially given the extensive cultural diversity found in the species. After all, chimps have dialects in their leaf gestures, such as leaf-clipping and leaf-tearing, which are used during sexual solicitation. This type of variation likely exists in goodbyes too. 

Despite the lack of attention paid historically to the tail-end of social interactions, the fact that leave-taking is found in wild primates has large implications. First, it allows the potential evolutionary contexts that promoted these complex communicative behaviours to be studied. It also highlights the social and cultural evolution of goodbyes—the way they have developed ubiquitously yet variably within cultures over time. It also fills a gap in our understanding of animal behaviour: it is not only humans who are aware of maintaining relationships with their group mates and who have developed purposeful signals to do so.

Not least, the finding removes another behaviour from the list of those considered exclusive to humans. A wave goodbye is no longer so curious. Now that the spotlight has turned on nonhuman leave-taking, we must continue to explore how it is expressed across the Animal Kingdom. How many species take leave and do any use waving? I have a feeling some of them will.