The model thereby suggests a possible evolutionary origin of modularity as a side effect of environmental canalization. OCT 21 2000. We study a model in which cooperation and defection coexist in a dynamical steady state. In our model, subpopulations of cooperators and defectors inhabit sites on a lattice. The chosen PD payoff allows cooperators, but not defectors, to maintain a homogeneous population.
Individuals mutate between types and migrate to neighboring sites with low probabilities.
The persistence of cooperation in this model can be explained in terms of the life cycle of a population at a site. This life cycle starts when one cooperator establishes a population. Then defectors invade and eventually take over, resulting finally in the death of the population. During this life cycle, single cooperators migrate to empty neighboring sites to found new cooperator populations. The dynamic persistence of cooperation ranges over a large section of the model's parameter space.