A mechanism for the Evolution of Altruism Among Non-kin: Positive Assortment Through Environmental Feedback

The evolution of cooperation often requires genetic similarity among interactors. For populations that are divided into groups such that a given trait affects all group members, this requires positive assortment of individuals into groups, i.e., that individuals are more similar to other group members than to the population at large. Several authors have claimed that mechanisms other than kinship could produce genetic similarity within groups, but this claim has not been generally accepted. Here we describe such a mechanism. The process of "environmental feedback" requires only that the cooperative trait affects the quality of the local environment, and that organisms are more likely to leave low quality than high quality environments. We illustrate this dynamic using an agent-based model of feeding restraint. The mechanism of environmental feedback appears to be a general one that could potentially play a role in the evolution of many kinds of altruism in nature.