Abstract

Group selection is said to occur when the traits of groups that systematically out-reproduce competing groups eventually come to characterize the species. Evolutionists have long disputed over the degree to which group selection is effective—that is, over the degree to which social group characteristics can be attributed to selection on these characteristics. The intractability of this controversy arises from three ambiguities in the natural selection metaphor that manifest themselves when that metaphor is shifted to the group level: (1) uncertainty about what constitutes the analogue for "flock" in the group level metaphor; (2) uncertainty about how to identify the group "parents" of offspring groups; and (3) uncertainty about what constitutes a group trait for the purposes of group selection. When group selection is specified as a theory about the evolution of emergent properties of groups through differential group productivity mediated by quantitative inheritance of group traits, these ambiguities disappear.