Altruism, malice and public goods: Does altruism pay?

Abstract

In recently published work, economist Gordon Tullock argues that the traditional kin selection argument for the evolution of altruism fails, due to what economists call the free rider problem. The altruistic sibling provides (in the terminology of economics) a public good. That is, the benefits of the altruistic act accrue to common and unrelated genes equally, but the costs are all borne by related genes. Thus, the unrelated genes receive a “free ride” and therefore increase in proportion. This paper shows that Tullock's result depends on the very unrealistic assumption that there is no crowding or scarcity limiting population and the altruists starting as a large proportion of the population. When a crowding constraint is added Tullock's argument is shown to be incorrect. Under a crowding constraint, an altruistic act imposes crowding costs on largely unrelated individuals. Further, a simple mathematical model of selection with crowding is constructed. The result is an interior solution. Depending on the parameters of the pay-off to altruism, equilibrium may occur with no altruists. But, if altruism pays, the equilibrium will require a mixture of altruists and non-altruists.