Exploring an Evolutionary Paradox: An Analysis of the "Spite Effect" and the "Nearly Neutral Effect" in Synergistic Models of Finite Populations

Forber and Smead (2014) analyze how increasing the fitness benefits associated with prosocial behavior can increase the fitness of spiteful individuals relative to their prosocial counterparts, so that selection favors spite over prosociality. This poses a problem for the evolution of prosocial behavior: as the benefits of prosocial behavior increase, it becomes more likely that spite, not prosocial behavior, will evolve in any given population. In this paper, I develop two game-theoretic models which, taken together, illustrate how synergistic costs and benefits may provide partial solutions to Forber and Smead’s paradox