Gene-Culture Coevolution of Prosocial Rituals

It has been argued that costly socially learned rituals have the potential to generate prosocial emotional responses arising from genetically based behavioral dispositions, hijacking these behavioral dispositions to solve otherwise intractable cooperation problems. An example is the innovation of synchronous movement rituals which seem to engage the same altruistic response as instinctual mimicry. Arguments against this hypothesis are based in the idea that cheap markers of altruistic intent (“Green Beards”)are vulnerable to manipulation from non-cooperating free-riders that are similarly marked. This paper formally models the gene-culture coevolutionary dynamics of a system in which a costly socially learned ritual practice coevolves with the genes underpinning the prosocial response. This takes a ‘genetic mismatch’ hypothesis (where fast evolution of socially learned behaviors create a temporary mismatch with the coevolving genes, which take longer to evolve to equilibrium) and models it dynamically. The genetic and cultural fitness equations are first analyzed for equilibrium and then simulations are used to predicting trajectories for both the socially learned behavior and the hijacked genetic trait over time. Relying on fast culture and slow genes, it demonstrates how high levels of ritual efficacy may be established, at least temporarily, through gene culture interaction. It also shows how longer term feedbacks on the genes from culture may lead to decreases in the prosocial gene in the population and reduced overall population mean fitness, despite high levels of altruism in the population.