Although about half of primate species play as adults with other adults, a team of international researchers has just unlocked a key factor in the reason why some don't. The answer lies in the type of society in which the animals live.

"Despotic and moderately despotic species are markedly less likely to exhibit adult-adult play than tolerant ones," according to the study recently published in Biology Letters.

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The results suggest that play and tolerance reinforce each other in a "virtuous circle." In tolerant groups, adult play becomes a strategic tool to negotiate complex relationships, build trust, and maintain group cohesion. In despotic systems, however, the risk of aggression makes play unstable, or even dangerous, effectively suppressing it.

Beyond the animal kingdom, the findings offer a revealing mirror for human societies. "We think these findings can help understand better human social, cultural, and political variation," Burghardt said.

The researchers draw parallels with hunter-gatherer groups, where egalitarianism fosters humor and play as non-coercive tools of social regulation. By contrast, human authoritarian systems, comparable to despotic primate societies, tend to inhibit creative and cooperative behaviors that do not align with political goals.

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