Marco the chimpanzee at the Center for Great Apes

Researchers from the University of California Los Angeles (UCLA), the Max Planck Institute of Animal Behavior (MPI-AB), Indiana University (IU), and the University of California San Diego (UCSD) have identified playful teasing behavior in four species of great apes. This behavior shares similarities with joking in humans, characterized by its provocative, persistent nature, and inclusion of play elements. The presence of playful teasing across all four great ape species suggests its evolutionary roots in the human lineage at least 13 million years ago.

Playful teasing, similar to joking, emerges in humans as early as eight months of age. Infants engage in repetitive provocations, such as offering and withdrawing objects as well as disrupting activities. In a study published in the Proceedings of the Royal Society B, researchers examined spontaneous social interactions among orangutans, chimpanzees, bonobos, and gorillas to identify teasing behaviors.

The study involved analyzing teasing actions, bodily movements, facial expressions, and responses from the targets of teasing. Teasers exhibited intentional provocative behaviors, often accompanied by playful characteristics. The researchers identified 18 distinct teasing behaviors, such as waving or swinging objects in the target’s field of vision, poking or hitting, and disrupting movements.

Although playful teasing shares similarities with play, it differs in several aspects. Teasing tends to be one-sided, initiated primarily by the teaser and rarely reciprocated. Additionally, apes almost never use play signals like the primate ‘playface’ or ‘hold’ gestures. Teasing occurs in relaxed contexts and involves repetition and elements of surprise, similar to teasing in human children.

To offer an explanation for this teasing behavior among animals, oxytocin (love hormone) may play a role in doing so as well as promoting positive social interactions. Oxytocin goes into effects by binding to specific oxytocin receptors in the brain such as G protein-coupled receptors (as learned in AP Biology). Oxytocin receptors then activates the primary signaling pathways, involving the phosphoinositide 3-kinase (PI3K) pathway. Activation of PI3K leads to the production of second messengers, which regulate various cellular processes that contributes to the warm and fuzzy feeling we get due to oxytocin.

The presence of playful teasing in great apes, resembling behaviors in human infants, suggests its existence in our common ancestor over 13 million years ago. This study sheds light on the importance of understanding the evolutionary origins of behavior and the need for conservation efforts to protect these endangered animals.

Personally, I can definitely attest to the evolutionary pass-down of these playful teasings as I still find myself engaging in the same behaviors, oftentimes scorned and unreciprocated.

What are your thoughts on these findings?