 The very idea of group selection is a controversial one. Many commentators have taken a sceptical view of group selection when underpinned by genetic inheritance, because of worries that competition based on genetic variation within groups will tend to undermine the effects of competition between groups. Several cultural evolutionists (e.g. Boyd and Richerson 2009, Henrich 2015) have argued that cultural inheritance processes are better able than processes of genetic inheritance to sustain between-group differences, for they believe there is good empirical and theoretical evidence that cultural processes can maintain within-group homogeneity in the face of various countervailing factors (immigration, unreliable imitation and so forth).