The Principle of Stasis: Why Drift is not a Zero-Force Law

Textbooks and most of the evolutionary literature talk about evolutionary forces acting on a population. The analog y was proposed by Elliott Sober (1984) who arg ues that evolutionary theory is a theory of forces because, in the same way that different forces of Newtonian mechanics cause chang es in the movement of bodies, evolutionary forces cause chang es in g ene and/or g enotype frequencies. As a result, selection, drift, mutation and mig ration would be the main forces or causes of evolution. This is what Maudlin (2004) calls “quasi-Newtonian theories”. These are characterized by shaping alike to Newtonian mechanics, whose main axis is the adoption of a Zero-Force Law (henceforth ZFL) which will tell us how the system would behave if forces were not acting on it. The main purpose of building “quasi-Newtonian” theories is to identify the causes that affect a physical system. That is why a ZFL is necessary.