Drift as a Force of Evolution: A Manipulationist Account

Abstract

Can evolutionary theory be properly characterised as a “theory of forces,” like Newtonian mechanics? One common criticism to this claim concerns the possibility to conceive genetic drift as a causal process endowed by a specific magnitude and direction. In this chapter, we aim to offer an original response to this criticism by pointing out a connection between the notion of force and the notion of explanatory depth, as depicted in Hitchcock and Woodward’s manipulationist account of causal explanation. In a nutshell, our argument is that since force-explanations can be consistently reframed as deep explanations and vice versa and the notion of drift can be characterised in manipulationist terms as constitutively intervening in evolutionary deep explanations, then drift-explanations can be consistently reframed as force-explanations, and drift can be properly considered as a force of evolution. Insofar as similar considerations may be extended also to other evolutionary factors – chiefly selection – our analysis offers an important support to the claim that evolutionary theory is a theory of forces.