 In a useful article, Elliott Sober (1991) suggests that theories of cultural evolution may have limited value for the work of social scientists, on the grounds that social scientists are primarily interested in explaining what makes individuals likely to adopt one idea, rather than another. They want to know, for example, why nineteenth-century Italian women decided that they would rather have two children than five, not what the population-level consequences of their decisions might be. Richerson and Boyd respond by saying that Sober’s argument assumes, erroneously, that ‘we are all good intuitive population thinkers’ (Richerson and Boyd 2005, 97). In Sober’s original article he points out that population thinking might save cultural evolutionary models from vacuity in just this way: