Ultimate explanations concern the adaptive rationale for organism design

My understanding is that proximate explanations concern adaptive mechanism and that ultimate explanations concern adaptive rationale. Viewed in this light, the two kinds of explanation are quite distinct, but they interact in a complementary way to give a full understanding of biological adaptations. In contrast, Laland et al. (2013)—following a literal reading of Mayr (Science 134:1501–1506, 1961)—have characterized ultimate explanations as concerning any and all mechanisms that have operated over the course of an organism’s evolutionary history. This has unfortunate consequences, such as allowing random drift to form the basis for ultimate explanations, and allowing proximate and ultimate explanations to bleed into each other until their distinction is meaningless. Here, I suggest Laland et al’s explanatory framework of “reciprocal causation” is not conducive to successful biological science, and that they have misunderstood key elements of the theory of Darwinian adaptation.