REPRODUCTIVE BRIBING AND POLICING EVOLUTIONARY MECHANISMS FOR THE SUPPRESSION OF WITHIN-GROUP SELFISHNESS

We show that a new, simple, and robust general mechanism For the socia l suppression of within-group selfishness Follows from Hamilton's rule applied in a multilevel selection approach to asymmetrical, two-perso n groups: If it pays a group member to behave selfishly (i.e., increas e its share of the group's reproduction, at the expense of group produ ctivity), then its partner will virtually always be favored to provide a reproductive ''bribe'' sufficient to remove the incentive for the s elfish behavior. The magnitude of the bribe will vary directly with th e number of offspring (or other close kin) potentially gained by the s elfish individual and inversely with both the relatedness r between th e interactants and the loss in group productivity because of selfishne ss. This bribe principle greatly extends the scope for cooperation wit hin groups. Reproductive bribing is more likely to be favored over soc ial policing for dominants rather than subordinates and as intragroup relatedness increases. Finally, analysis of the difference between the group optimum for an individual's behavior and the individual's inclu sive fitness optimum reveals a paradoxical feedback loop by which brib ing and policing, while nullifying particular selfish acts, automatica lly widen the separation of individual and group optima for other beha viors (i.e., resolution of one conflict intensifies others).