Multilevel Causation and the Extended Synthesis

In this article we argue that the classical—linear and bottom-up directed—models of causation in biology, and the “proximate/ultimate” dichotomy, are inappropriate to capture the complexity inherent to biological processes. We introduce a new notion of “multilevel causation” where old dichotomies such as proximate/ultimate and bottom-up/top-down are reinterpreted within a multilevel, web-like, approach. In briefly reviewing some recent work on complexity, EvoDevo, carcinogenesis, autocatalysis, comparative genomics, animal regeneration, phenotypic plasticity, and niche construction, we will argue that such reinterpretation is a necessary step for the advancement of the “Extended Synthesis”.