Culture is critical in driving orangutan diet development past individual potentials

Humans accumulate extensive repertoires of culturally-transmitted information, reaching breadths exceeding any individual’s innovation capacity (culturally-dependent repertoires). It is unclear whether other animals require social learning to acquire adult-like breadths of information in the wild, including by key developmental milestones, or if animals are capable of constructing their knowledge repertoires primarily through independent exploration. We investigated whether social learning mediates orangutans' diet-repertoire development, by translating an extensive dataset describing wild orangutans’ behavior into an empirically-validated experimental simulation. Diets only reliably developed to adult-like breadths when simulated immatures benefitted from multiple forms of social learning. Moreover, social learning was required for diets to reach adult-like breadths by the maximum age immatures become independent from their mothers. Social learning is therefore integral for the timing and outcomes of orangutans’ broad-scale diet learning, demonstrating that culture can profoundly influence other animals’ development. We discuss prospective avenues for researching cultural-repertoire-building in hominids and other species.