Standard evolutionary and economic approaches to understanding cooperation assume that individual self-interest is the natural state of the world. In that view, cooperation is only viable among individuals with sufficient cognitive complexity to overcome the 'natural' state of defection through such abilities as individual recognition, memory, punishment, commitment and other incentive and enforcement systems. The present paper challenges the view that complex cognitive abilities are necessary for the evolution of cooperation by describing the findings of two models of the evolution of cooperation: the Walk Away and environmental feedback models. In these models, individuals simply leave regions in which they receive low returns. Because the presence of defectors reduces the quality of the local environment, regions with defectors are less stable than regions of cooperators. The individual level behavior in these models generates aggregate dynamics that promote positive assortment and selection for cooperation via group selection. The basic findings of the Walk Away and environmental feedback models suggest that complex cognitive abilities may not be necessary for the evolution of cooperation and that cooperation may be the 'state of nature' in a wider variety of contexts than previously assumed.