Darwinism in the twentieth century: Productive encounters with saltation, acquired characteristics, and development

Abstract

Darwinism is one of several research traditions in evolutionary biology. I identify it, both before and after its unification with genetics, with Darwin's theory of descent by natural selection from a common ancestor. Other traditions include saltationism/mutationism, Lamarckism, and evolutionary developmentalism ("evodevo"). I argue that Darwinism's continued dominance in evolutionary science reflects its proven ability to interact productively with these other traditions, an ability impressed on it by its founder's example. Evolution by sudden leaps (saltations) is alien to the spirit of Darwinism, but Darwinism advanced its own agenda by incorporating and subverting saltationist themes. Similarly, Lamarckism's belief in the heritability of acquired characteristics has been discredited, but some of the facts to which it seems congenial reappear in genetic Darwinism as phenotypic plasticity and niche construction. These examples help assess challenges to Darwinism's hegemony currently arising from the role of regulatory genes and epigenetic factors in development. Rather than executing already entrenched genetic programs and relying on chance mutation to initiate evolutionary change, the developmental process appears to generate heritable variations that ab initio respond to environmental factors in an adaptive way.