'Why' functions (in evolutionary biology and cultural anthropology)

Appeal to the function of a trait, behavior or cultural practice is a central component of many proposed explanations in biology and cultural anthropology. The "received view" in philosophy of science has seen such attempts to explain as not genuinely explanatory. I argue, to the contrary, that an etiological approach to functional explanation provides an account of the legitimate explanatory import of functions.;Having presented an account of the general requirements, I then apply the analysis to the functional explanations of traits by evolutionary biology, of human social behaviors by sociobiology, and of cultural practices by cultural ecology. I argue that the biological function of a trait explains its presence if that trait is an adaptation, i.e., is the result of evolution by natural selection. In this context, the issues of the unit and levels of selection are also discussed. Sociobiological explanations of human behavior appeal to consequences for reproductive success. A problem is raised for such explanations by the possibility of detaching cultural transmission of human behavior from genetic transmission. Thus, to be justified, sociobiological explanations must provide evidence to exclude this possibility. Ecological explanations of cultural practices appeal to consequences for the continued survival of a cultural group in relation to specified ecological conditions. An analysis is presented of the variety of selection and transmission models implicit in these explanations.;The ascription of a function to an item explains why the item is there if (i) the function is a consequence of the item's presence and (ii) having that consequence is causally relevant to the item's presence. The second condition can be met if the item is selected from a variety of options for having the consequences of interest. A special type of causal background is thus necessary to underwrite functional explanations. Whether the item being explained is an artifact, trait, social behavior or cultural practice, if it has the appropriate etiology, its presence can be explained by its function.