In more hierarchical and authoritarian societies, play among adults tends to disappear. This is the main finding of an international study coordinated by the University of Pisa, which shows that the level of social despotism is the key factor in determining the presence or absence of play among adult primates, regardless of their evolutionary history.
The research, published in Biology Letters, analysed 37 primate species, including chimpanzees, bonobos, macaques, lemurs and monkeys. In more tolerant species, adult play is very common (in over 90% of cases), whereas in more authoritarian ones it is rare or absent. By contrast, physical characteristics such as body weight or sex differences do not influence this behaviour.
“What clearly emerges is that it is not so much ‘who you are’ in evolutionary terms that makes the difference, but ‘how you live’ from a social perspective,” explains Elisabetta Palagi, Professor in the Department of Biology at the University of Pisa and coordinator of the study. “Even animals that are very similar can behave differently depending on how tolerant their social groups are. In more rigid and authoritarian societies, play among adults tends to disappear, along with the social benefits it brings, such as reduced conflict, stronger social bonds and increased cooperation.”
“To classify primate societies, we assessed three key dimensions of social relationships,” adds Martina Francesconi, PhD candidate in the Department of Biology at the University of Pisa. “These include grooming — that is, mutual cleaning of the fur, which acts as a key social bonding mechanism — conflict management, meaning reconciliation and consolation dynamics after a clash, and the rigidity of dominance hierarchies.”
“The results show striking parallels with human societies, as demonstrated by anthropological studies used for comparison,” Palagi concludes. “In hunter-gatherer populations, play and humour among adults are associated with cooperation and non-coercive forms of social regulation, whereas in more authoritarian systems these expressions tend to be limited, with potential effects on creativity and mutual trust.”
The study, one of the most comprehensive comparative analyses on this topic, was coordinated by the Ethology Unit of the Department of Biology at the University of Pisa, under the leadership of Elisabetta Palagi, with a significant contribution from PhD candidate Martina Francesconi. It also involved the University of Turin, the University of Tennessee (USA) and the University of Lethbridge (Canada).
The team reviewed scientific literature from 1965 to 2024, analysing the data using advanced statistical models. The research was developed within workshops and research groups dedicated to the study of the evolution of play and was supported by the PRIN 2022 project “LOL! The evolutionary roots of human laughter”, funded by the European Union – Next Generation EU.
