In comparative primatology and evolutionary psychology, xenophilic altruism — voluntary, unrewarded helping directed at unfamiliar conspecifics — is used as a test case for whether human prosociality is a species-unique cultural product or a phylogenetically inherited trait. The theory holds that if a closely related ape lineage independently exhibits both costly helping of strangers and emotional contagion toward strangers, then at least part of the human capacity for altruism has a biological, shared-ancestry basis rather than a purely cultural one. The supporting mechanism is emotional contagion, operationalized through contagious yawning as a behavioral proxy for empathic responsiveness, whose familiarity bias (or its absence) indexes the social breadth of empathy in a species.
In comparative primatology and evolutionary psychology, xenophilic altruism — voluntary, unrewarded helping directed at unfamiliar conspecifics — is used as a test case for whether human prosociality…