Influences on population survival.

<p>(A) The percent of runs in which the population survived as a function of the initial cooperator frequency, for <i>β</i> = 100. (B) The effect of both high cooperator frequency and high genetic quality on population survival for high costs of childrearing compared with the baseline model. Initial conditions in the “high fitness” condition were a cooperator frequency of 90% and a mean genetic quality of 0.86, compared with 50% cooperators and mean genetic quality of 0.5 in the baseline condition.