The Price equation and the unity of social evolution theory

Abstract

The Price equation has been entangled with social evolution theory from the start. It has been used to derive the most general versions of kin selection theory, and Pricehimselfproduced a multilevel equation which providesan alternative formulation of social evolution theory, dividing selection into components between and within groups. In this sense, the Price equation forms a basis for both kin and group selection, so often pitted against each other in the literature.Contextual analysis and the neighbour approach are prominent alternatives for analysing group selection. I discuss these four approaches to social evolution theory and their connections to the Price equation, focusing on their similarities and common mathematical structure. Despite different notations and modelling traditions, all four approaches are ultimately linked by a common set of mathematical components, revealing their underlying unity in a transparent way. The Price equation can similarly be used in the derivation of streamlined, weak selection social evolution modelling methods. These weak selection models are practicaland powerful methods for constructing models in evolutionary and behavioural ecology, they can clarify the causalstructure of models, and can be easily converted between the four social evolution approaches just like their regression counterparts.