Despotism trumps phylogeny in explaining suppression of play among adults in non-human primates

Adult–adult social play is unevenly expressed across human populations and primate species, raising the question of why some societies sustain such play while others do not. We tested whether adult–adult play is shaped by morphology, phylogeny, social structure or social style in 37 primate species, using Bayesian logistic regression with a phylogenetic random effect. Adult play was not predicted by female body mass or sexual dimorphism, which are phylogenetically conserved. Social style was the key factor: tolerant species were more likely to exhibit the behaviour than despotic ones, with intermediate probabilities in moderately despotic species. Phylogenetic analyses further showed that closely related species tend to resemble one another in their likelihood of adult–adult play, and that this phylogenetic signal persists even after accounting for the other predictors. Model comparisons consistently favoured social style over social structure, indicating that it better captures the conditions that enable adult–adult play. Adult–adult play, and tolerance may form a positive feedback loop, while despotic systems seem to inhibit both play and its potential social benefits. This pattern mirrors human cultural variation, in which authoritarian regimes suppress playful and creative expression.