We calculate the equilibrium fraction of cooperators in a population in which payoffs accrue from playing a single-shot prisoner's dilemma game. Individuals who are hardwired as cooperators or defectors are randomly matched into pairs, and cooperators are able to perfectly find out the type of a...

We demonstrate how altruism can surge in a population of nonaltruists. We assume that each individual plays a one-shot prisoner's dilemma game with his or her sibling, or with a stranger, and that the probability that an individual survives to reproduce is proportional to his or her payoff in...

We calculate the equilibrium fraction of cooperators in a population in which payoffs accrue from playing a single-shot prisoner's dilemma game. Individuals who are hardwired as cooperators or defectors are randomly matched into pairs, and cooperators are able to perfectly find out the type of a...

In a haystack-type representation of a heterogeneous population that is evolving according to a payoff structure of a prisoner’s dilemma game, migration is modeled as a process of “swapping” individuals between heterogeneous groups of constant size after a random allocation fills the...