 By contrast, practitioners of the research program that has become known as Evolutionary Psychology are much more concerned with mental structure and evolved psychological mechanisms, and readily discuss some forms of cultural variation (Barkow, Cosmides, &amp; Tooby 1992; also see Hagen 2015). Evolutionary Psychologist’s approach to explaining human behavioral variation builds on the more general notion of phenotypic plasticity. The approach emphasizes that phenotypic plasticity (of the behavioral phenotype, but also of morphological, physiological, and other dimensions of phenotypic expression) is found not just in humans, but in almost all organisms. Mechanisms that underlie such plasticity allow individuals with similar genotypes to express different phenotypes, and thus to flexibly adapt to different environments in a variety of ways. For instance, researchers have appealed to this kind of interaction between environmental differences, on the one hand, and mechanisms underlying phenotypic plasticity, on the other, to explain systematic patterns of variation in the clutch sizes of members of the same species of bird found in different geographical regions (Tooby &amp; Cosmides 1992). Evolutionary Psychologists offer explanations with a similar form for many instances of human variation, such as regional differences in the distribution of values. One such account holds that the prevalence in some groups of certain kinds of values and norms—collectivist or exclusivist—can be explained as an adaptive response evoked by the salience of cues indicating high pathogen threat in the group’s environment. Alternatively, the prevalence in other groups of contrasting values and norms—individualistic or inclusivist—are explained by the absence of such cues, and thus an environment that allows the expression of a different adaptive phenotype (Schaller &amp; Park 2011; also see Buchanan &amp; Powell 2016; cf. Gelfand et al. 2011; House et al. 2020).