The relationship between kin and group selection is a contested issue in evolutionary theory, and matters are not helped by a tendency to conflate questions of methodology with questions of causality. Drawing inspiration from W. D. Hamilton, Birch suggests we think about the distinction between kin and group selection in terms of differences of degree in the structural features of populations. Birch further argues that we can usefully draw a parallel distinction in the case of cultural evolution. Cultural group selection, which involves competition between stable, well-defined “tribes", has received a great deal of attention in recent years. Cultural kin selection, which relies on kinship relations in more loosely structured social networks, has been largely neglected. Birch argues that cultural kin selection deserves more attention than it has so far received. In particular, it may help explain how the “tribal” social structure presupposed by models of cultural group selection originally came to exist.