The Value of Price

The Price equation provides a comprehensive representation of evolutionary processes. Since its original formulation by George Price, it has been used to model a variety of phenomena in quantitative genetics and related fields. However, there is no consensus on the explanatory power of the equation. In this article we aim to clarify its place within modern evolutionary theory. To this end, we first state the basic concepts from which the Price equation can be derived as a theorem. From this axiomatization, we conclude that the Price equation is not explanatory in itself. It merely provides a phenomenological description of evolutionary processes. We argue that its role is analogous to that of Galilean kinematics in classical mechanics. Both the Price equation and Galilean kinematics function as conceptual frameworks that define the basic features of the behavior of a class of systems. Practitioners are encouraged to theorize further on these frameworks to find the possible explanation of this behavior in various specific scenarios. Thus, despite its phenomenological character, the Price equation integrates different fields of evolutionary biology by providing a common formalization of their shared explanandum.