Apes play and tease each other, suggesting that humor has evolutionary origins 

In a new study, researchers have documented playful teasing among great apes, suggesting that the roots of humor may stretch far back into our evolutionary history. 

The collaborative research was conducted by a team of cognitive biologists and primatologists led by the Max Planck Institute of Animal Behavior. 

The experts have unveiled fascinating insights into the social dynamics of orangutans, chimpanzees, bonobos, and gorillas, marking a significant milestone in our understanding of primate behavior.

Role of humor in apes and humans

The study draws parallels between human joking and ape teasing behaviors, highlighting their provocative, persistent nature, and the incorporation of elements of surprise and play. 

This similarity suggests that the foundational aspects of humor may have evolved in the human lineage at least 13 million years ago, predating the development of language and providing a new lens through which to view the cognitive capabilities of our closest relatives in the animal kingdom.

Joking, an integral component of human social interaction, relies heavily on social intelligence, the anticipation of future actions, and the recognition and appreciation of the violation of expectations. 

Playful teasing, observed in human infants as young as eight months, shares much with joking. Both include provocative, repetitive actions that involve surprise and violate social norms. 

The study indicates that such behavior in great apes represents a cognitive precursor to the more complex human joking.

“Great apes are excellent candidates for playful teasing, as they are closely related to us, engage in social play, show laughter and display relatively sophisticated understandings of others’ expectations,” said study first author Isabelle Laumer, a postdoctoral researcher at UCLA.

How the study was conducted

The researchers analyzed spontaneous social interactions among great apes that exhibited characteristics of playful, mildly harassing, or provocative behavior. 

The experts focused on the teaser’s actions, body movements, facial expressions, and the responses from those being teased, seeking evidence of intentionality and the desire to provoke a reaction.

The findings revealed that all four great ape species engage in intentionally provocative behaviors that are frequently playful. 

The study identified 18 distinct behaviors aimed at provoking a response or attracting attention, such as waving or swinging body parts or objects, hitting or poking, staring, disrupting movements, or pulling on hair. 

These actions, often persistent and one-sided, rarely elicited reciprocal play signals from the targets, highlighting a distinction from more mutual forms of play.

What the research team learned

“It was common for teasers to repeatedly wave or swing a body part or object in the middle of the target’s field of vision, hit or poke them, stare closely at their face, disrupt their movements, pull on their hair or perform other behaviors that were extremely difficult for the target to ignore,” said study senior author Professor Erica Cartmill of UCLA.

The study authors noted that although playful teasing took many forms, it differed from play in several ways. “Playful teasing in great apes is one-sided, very much coming from the teaser often throughout the entire interaction and rarely reciprocated,” explained Cartmill.  

“The animals also rarely use play signals like the primate ‘playface,’ which is similar to what we would call a smile, or ‘hold’ gestures that signal their intent to play.”

Apes and the evolutionary implications of humor

This research builds on observations by Jane Goodall and other field primatologists, systematically studying behaviors that had been noted anecdotally for years. 

The evolutionary implications of the findings are profound, suggesting that playful teasing and its cognitive prerequisites were likely present in the last common ancestor of humans and great apes.

This not only sheds light on the evolution of humor and social interaction but also underscores the deep connections we share with great apes.

“From an evolutionary perspective, the presence of playful teasing in all four great apes and its similarities to playful teasing and joking in human infants suggests that playful teasing and its cognitive prerequisites may have been present in our last common ancestor, at least 13 million years ago,” explained Laumer. 

“We hope that our study will inspire other researchers to study playful teasing in more species in order to better understand the evolution of this multifaceted behavior. We also hope that this study raises awareness of the similarities we share with our closest relatives and the importance of protecting these endangered animals.”

The study is published in the journal Proceedings of the Royal Society B Biological Sciences. 

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