A Mutation Threshold for Cooperative Takeover.

One of the leading theories for the origin of life includes the hypothesis according to which life would have evolved as cooperative networks of molecules. Explaining cooperation-and particularly, its emergence in favoring the evolution of life-bearing molecules-is thus a key element in describing the transition from nonlife to life. Using agent-based modeling of the iterated prisoner's dilemma, we investigate the emergence of cooperative behavior in a stochastic and spatially extended setting and characterize the effects of inheritance and variability. We demonstrate that there is a mutation threshold above which cooperation is-counterintuitively-selected, which drives a dramatic and robust cooperative takeover of the whole system sustained consistently up to the error catastrophe, in a manner reminiscent of typical phase transition phenomena in statistical physics. Moreover, our results also imply that one of the simplest conditional cooperative strategies, "Tit-for-Tat", plays a key role in the emergence of cooperative behavior required for the origin of life.