Explanatory Domains and Reciprocal Causation: How (not) integrate development and evolution

A common explanatory error in science concerns the conflation of the epistemological roles between two domains. Here we will address a specific case: when explanations of development replace evolutionary explanations or vice versa. Ernst Mayr famously distinguished between proximate and ultimate causal explanations in biology. His view was central to the Modern Synthesis’ exclusion of development from evolutionary theory. Nonetheless, the explanatory role of developmental processes in evolution is a central theme in current theoretical biology which has prompted several revisions of Mayr’s distinction. Here we will review these reviewers to determine whether the integration of development and evolution is based on an appropriate reinterpretation of Mayr’s distinction. In many cases, revisionists suggest an interactionist alternative, in which proximate and ultimate causes interact to produce evolved traits. The most frequent interactionist account relies on the idea of reciprocal causation. We will argue that this perspective is still problematic and that the boundaries between explanatory domains are crossed. Instead, we should rethink Mayr’s distinction by adopting an alternative view of evolutionary causation, the so-called Statisticalist view, which maintains that the only level of causation is the individual level. By ruling out two different levels of causation, this framework is appropriate to avoid fallacious explanations and reconsider reciprocal causation entirely as a proximate phenomenon. We introduce the concept of “statistical reciprocity” to explain the statistical effects of reciprocal causality in populations and outline some ideas of “population ontogenetics” as a prominent framework for unifying development and evolution beyond interactionist positions.