Continuous-time models of group selection, and the dynamical insufficiency of kin selection models

Abstract

Traditionally, the process of group selection has been described mathematically by discrete-time models, and analyzed using tools like the Price equation. This approach makes implicit assumptions about the process that are not valid in general, like the central role of synchronized mass-dispersion and group re-formation events. In many important examples (like hunter–gatherer tribes) there are no mass-dispersion events, and the group-level events that do occur, like fission, fusion, and extinction, occur asynchronously. Examples like these can be fully analyzed by the equations of two-level population dynamics (described here) so their models are dynamically sufficient. However, it will be shown that examples like these cannot be fully analyzed by kin selection (inclusive fitness) methods because kin selection versions of group selection models are not dynamically sufficient. This is a critical mathematical difference between group selection and kin selection models, which implies that the two theories are not mathematically equivalent.