Solving the prisoner's dilemma trap in Hamilton's model of temporarily formed random groups

TL;DR

This paper analytically demonstrates that strong altruism can evolve in Hamilton's model of temporary random groups, especially under biparental reproduction and low cooperation costs, challenging previous assumptions.

Contribution

It shows that strong altruism can evolve in Hamilton's original model without requiring punishment or assortment, providing a new perspective on cooperation emergence.

Findings

Strong altruism evolves in biparental reproduction scenarios.

Cooperation becomes the only stable strategy when costs are low and benefits are high.

Reassesses cooperation in viral co-infection contexts.

Abstract

Explaining the evolution of cooperation in the strong altruism scenario, where a cooperator does not benefit from her contribution to the public goods, is a challenging problem that requires positive assortment among cooperators (i.e., cooperators must tend to associate with other cooperators) or punishment of defectors. The need for these drastic measures stems from the analysis of a group selection model of temporarily formed random groups introduced by Hamilton nearly fifty years ago to describe the fate of altruistic behavior in a population. Challenging conventional wisdom, we show analytically here that strong altruism evolves in Hamilton's original model in the case of biparental sexual reproduction. Moreover, when the cost of cooperation is small and the amplified contribution shared by group members is large, cooperation is the only stable strategy in equilibrium. Thus, our results provide a solution to the `problem of origination' of strong altruism, i.e. how cooperation can take off from an initial low frequency of cooperators. We discuss a possible reassessment of cooperation in cases of viral co-infection, as cooperation may even be favored in situations where the prisoner's dilemma applies.