Abstract

In 1961, Ernst Mayr published a highly influential article on the nature of causation in biology, in which he distinguished between proximate and ultimate causes. Mayr argued that proximate causes (e.g. physiological factors) and ultimate causes (e.g. natural selection) addressed distinct ‘how’ and ‘why’ questions and were not competing alternatives. Here I will argue that the distinction between cause and function is important, and retains explanatory value, but that it can be made without Mayr’s terminology, which is also ambiguous, dated and brings with it intellectual baggage. The adoption of Mayr’s heuristic led to the widespread belief that ontogenetic processes are irrelevant to evolutionary questions, a belief that has hindered progress within evolutionary biology, forged divisions between evolutionary biology and adjacent disciplines, and adversely affected several contemporary debates in biology (e.g. over evolution and development, niche construction, cooperation, the evolution of language). In this talk I will expand on my collaborators’ and my earlier (Laland et al., 2011, Science, 334: 1512-16) argument that Mayr’s dichotomous formulation has now run its useful course, and that evolutionary biology would be better served by a concept of reciprocal causation, which is better placed to recognize the roles that behavior, development and plasticity play in evolution.