Evolutionary Psychology: Adaptationist, Selectionist, and Comparative

ion chosen to escape the locally and historically particular and thus to describe human (or other species') "nature." In other words, the entities and processes of central interest to psychologists are hypothesized biological adaptations. As Buss aptly stresses, evolution by selection is the only known process capable of producing such adaptations. It follows that keeping abreast of conceptual developments in evolutionary biology can be an aid to psychologists, as it is to other life scientists. In this commentary, we expand on the implications of evolutionary thinking for psychology, emphasizing three points that are not explicit in Buss's treatment. The first is that assumptions and hypotheses about adaptive function are inescapable in the life sciences, including psychology, and are nothing to be ashamed of; the popular notion that "hard sciences" eschew such "teleological" ideas is both wrong and an impediment to the generation of sophisticated hypotheses about complex systems. Our second point is that sound adaptationist thinking is facilitated by explicit consideration of the process of evolution by selection. Our third point is that evolutionary thinking is often especially illuminating in the context of cross-species comparative analyses, particularly with respect to convergent rather than homologous attributes. Adaptationism Is Essential in the Life Sciences The past three decades have witnessed an explosion of adaptationist, selectionist theorizing and research in evolutionary (especially behavioral) biology. The word adaptationist refers to explicit consideration of how attributes, including such psychological attributes as decision-making and information-processing algorithms, are suited to their functions. Selectionist implies explicit consideration of how natural selection and sexual selection operate to shape adaptations over generations. These developments in evolutionary behavioral biology have been called the sociobiological revolution, although most contemporary participants prefer to call their field behavioral ecology. Adaptationist thinking is a ubiquitous and inescap able element of investigation in the life sciences. As the eminent evolutionary biologist Ernst Mayr (1983) noted, for example, in response to a misguided complaint about adaptationism within biology: The adaptationist question, "What is the function of a given structure or organ?'has been for centuries the basis forevery advance inphysiology. If it had not been for the adaptationist program, we probably would still not yet know the functions of thymus, spleen, pituitary, and pineal. Harvey's question "Why are there valves in the veins?'was a major stepping stone in his discovery of the circulation of blood. If one answer turned out to be wrong, the adaptationist program demanded another answer until the true meaning of the structure was established or until it could be shown that this feature was merely an incidental byproduct of the total genotype. (Mayr, 1983, p. 328) Assumptions and hypotheses about adaptive function pervade psychology for the same reason that they pervade physiology-because the mechanisms under study are so obviously organized in such a way as to "achieve something." Investigation is guided by conceptions of what that "something" might be-whether signal detection, or perceptual constancy, or self-actualization, or relief from cognitive dissonance. UnfortuD ow nl oa de d by [ M cM as te r U ni ve rs ity ] at 0 6: 48 0 1 A ug us t 2 01 6