Old joke: Apes exhibit teasing behaviour, suggesting an ancient trait

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A lively young chimpanzee playfully slaps an adult family member on the back, then swiftly retreats, glancing back to gauge the reaction to his cheeky act. Not receiving an immediate response, the chimp, named Azibo, rolls back and delivers another slap, finally provoking a reaction. The distracted adult half-heartedly waves a hand in Azibo's direction, dismissing the mischievous youth, though not for long.

This is just one of many scenes that scientists have studied that show apes playfully teasing each other, just like young human children do. The scene was witnessed at the Leipzig Zoo in Germany. Based on a previous study, the scientists hypothesise that the cognitive conditions for joking most likely originated in a common ancestor millions of years ago, as all four species of great apes display teasing behaviour.

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The researchers documented a variety of playful antics, ranging from one ape offering an object only to retract it at the last moment to preventing their counterpart from obtaining a desired item. Some tricksters simply defied instructions, while others enjoyed poking. Much of this behaviour mirrors that of human children, manifesting from around eight months in the most precocious individuals.

Described as existing between normal play and aggression, playful teasing involves anticipating others’ reactions and relishing the act of defying expectations, according to the study published in the journal Proceedings of the Royal Society B.

The researchers were shocked, according to lead author Isabelle Laumer, that this lively taunting rarely resulted in violent action. Laumer, a cognitive scientist and primatologist at Germany's Max Planck Institute of Animal Behavior noted that the adults reacted calmly to similar behaviour.

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Analysing 75 hours of video footage featuring chimpanzees, bonobos, gorillas, and orangutans engaged in playful antics in zoos, the research team identified 18 different teasing behaviours, with chimpanzees prominently involved in humorous activities such as slapping dozing adults or obstructing their path.

Orangutans displayed a talent for hair-pulling, while gorillas favoured the traditional provocation of a shove.

In the majority of interactions, a young ape would start making playful motions towards an adult and would keep doing so until they got a response. During 25 per cent of the exchanges, the targeted adult took the opposite approach and teased the child in return, which occasionally resulted in more traditional play activities including wrestling, chasing, mock-biting, or tickling.

The researchers noted that while playful interactions need the involvement of both sides, lighthearted teasing is by its very nature asymmetrical, with one person picking on the other. They proposed that at least 13 million years ago, the common ancestor of modern primates and humans probably possessed the cognitive capacity for such humour.

(With inputs from agencies)