Does the Extended Evolutionary Synthesis entail extended explanatory power?

Jan Baedke (Ruhr Universität)

Abstract: Biologists and philosophers of science have recently called for an extension of evolutionary theory. This novel, so-called ‘Extended Evolutionary Synthesis’ (EES) seeks to integrate more seriously developmental studies in fields such as evolutionary developmental biology (Evo-Devo), epigenetics, and niche construction theory (NCT) into standard evolutionary theory (SET). Advocates of the EES agree that this new perspective offers better explanations compared to the prevailing SET. Still, why this is necessary the case is anything but clear. Usually, it is tacitly assumed that the pluralist structure of the EES, its different problem agenda, and/or a growing body of evidence for the evolutionary relevance of developmental phenomena secures EES’s superior explanatory status. However, what is usually neglected in this debate is discussing what actually the explanatory standards of the EES are and how they differ from prevailing standards in evolutionary biology. In other words, what is considered to be a good explanation according to the EES compared to the SET? This paper addresses this question in detail. A contrastive framework is presented that allows evaluating the explanatory power of different evolutionary explanations. This account is able (i) to identify and visualize internal differences in the explanatory standards within the EES (varying across epigenetics, Evo-Devo, and NCT), and (ii) to clarify according to which criteria (why) and in which context (when) evolutionary explanations of the EES are better than those of the SET. This information is crucial for the EES to face epistemic challenges of theoretical integration that lie ahead.