Daniel M.T. Fessler: UCLA Department of Anthropology

The evolutionary study of mind and behavior has benefited enormously from the functionality heuristic, i.e., the assumption that mental mechanisms can usefully be understood as well-designed solutions to recurrent adaptive problems. While virtually every investigator in this area acknowledges the importance of Tinbergen’s (1963) Four Levels of Explanation, in practice, emphasis in evolutionary psychology is invariably placed primarily on ultimate explanations. Although this is a productive starting point, because evolution involves the gradual modification of existing designs, the functionality heuristic will frequently lead investigators to under-emphasize, or even overlook entirely, constraints on optimality entailed by phylogeny. Likewise, even when high levels of functionality are, in fact, observed, the functionality heuristic will often fail to explain many features of the adaptation at issue, features that diminish efficiency even if they do not influence effectiveness. The study of emotions provides an opportunity to illustrate the utility of combining ultimate and phylogenetic perspectives in investigating the mind. A hybrid approach to emotions can illuminate otherwise puzzling combinations of qualia, display, cognition, and behavior, and suggests areas where we might expect constraints on optimality. Additionally, such an approach can productively generate predictions concerning the nature of emotions across species and across taxa, holding the promise of a broadly comparative evolutionary affective science that pinpoints both the commonalities and the divergences between our emotions and those of other organisms. These possibilities will be illustrated through a discussion of research on the evolutionary psychology of disgust.