Humans Aren't the Only Jokers on the Planet

You would think poking or slapping a great ape would be ill-advised. But the young chimpanzees, bonobos, gorillas, and orangutans who tease their adult counterparts are rarely met with aggression. That's because, according to a new study, even great apes know when a joke is a joke. Researchers analyzed 75 hours of video of chimpanzees, bonobos, gorillas, and orangutans in zoos in San Diego and Leipzig, Germany, and found playful teasing is commonplace, whether it involves a young orangutan swinging a rope at her father's head or a young chimpanzee smacking an adult relative on the back before running away and checking for a reaction, per AFP and the Washington Post.

Researchers logged 18 types of teasing. Juvenile apes were found to poke, hit, pull hair, do the opposite of what they were told, and offer an object to another, only to pull it away, per AFP. If there was no reaction, they'd usually try again. The teased apes responded with anger in less than 5% of cases. In 25% of interactions, "the initial target turned the tables on the prankster, teasing them right back," per AFP. Sometimes it would result in play, in the form of wrestling, tickling, or chase. The behavior raises a lot of questions "about what animals understand about other animals' minds, expectations and the strength of their relationships," Erica Cartmill, senior author of the study published Wednesday in Proceedings of the Royal Society B, tells the Post.

Chimpanzees seemed most fond of teasing, per AFP. This wasn't a huge surprise as primatologist Jane Goodall previously observed young chimps messing with their elders in various ways. But as the behavior was observed across all four species of great apes, the study authors conclude the "cognitive prerequisites for joking" likely evolved in the common ancestor of humans and all modern primates at least 13 million years ago. It's unclear how teasing benefits great apes, though it could help juveniles learn social skills, per the Post. As lead study author Isabelle Laumer tells CNN, "It seems that because the teaser is closely watching and observing the target's reaction ... maybe it's something like, 'How far can I go until something bad happens?'" (More apes stories.)