Abstract:

Recent years have seen renewed interest in the role of religious systems as drivers of the evolution of cooperation in human societies. One suggestion is that cultural traditions of ancestor worship might have evolved as “descendant-leaving strategies” of ancestors by encouraging increased altruism particularly between distant kin. Specifically, ancestors might have been able to establish parental manipulation of kin recognition and perceived relatedness as a traditional behaviour via a mechanism of cultural transmission exploiting social learning biases, thereby maximising their long-term inclusive fitness. Here, a demographically explicit, mathematical model has been developed to quantify the resulting increase in altruism and concomitant “ancestor-descendant conflict”, and to determine the evolutionary feasibility of cultural norms promoting altruism among co-descendants. The analysis reveals that such norms could indeed drive an overall increase in altruism with potential for conflict and that they can be favoured by natural selection under a range of conditions, with the inclusive-fitness costs of enacting an inappropriately high level of altruism being offset by inclusive-fitness benefits derived from the facilitation of kin recognition. These findings reaffirm that cultural institutions can generate adaptive behaviours by providing extrasomatically stored, fitness relevant information and promote an increase in cooperation not expected via genetic selection.

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