Why selection and drift might be distinct

In this paper, it is argued that selection and drift might be distinct. This contradicts recent arguments by Brandon (2005) and Matthen and Ariew (2002) that such a distinction "violates sound probabilistic thinking" (Matthen and Ariew 2002, 62). While their arguments might be valid under certain assumptions, they overlook a possible way to make sense of the distinction. Whether selection and drift can be thought of as causally distinct, I argue, depends on the source of probabilities in natural selection. In particular, if the probabilities used in defining fitness values are at least partly a result of abstracting from or ignoring certain features of the environment, then selection and drift might in fact be causally distinct.