Why Don't Zebras Have Machine Guns? Adaptation, Selection, and Constraints in Evolutionary Theory

Document Type

Article

Publication Date

2008

Abstract

In an influential paper, Stephen Jay Gould and Richard Lewontin (1979) contrasted selection-driven adaptation with phylogenetic, architectural, and developmental constraints as distinct causes of phenotypic evolution. In subsequent publications Gould (e.g., 1997a,b, 2002) has elaborated this distinction into one between a narrow "Darwinian Fundamentalist" emphasis on "external functionalist" processes, and a more inclusive "pluralist" emphasis on "internal structuralist" principles. Although theoretical integration of functionalist and structuralist explanations is the ultimate aim, natural selection and internal constraints are treated as distinct causes of evolutionary change. This distinction is now routinely taken for granted in the literature in evolutionary biology. I argue that this distinction is problematic because the effects attributed to non-selective constraints are more parsimoniously explained as the ordinary effects of selection itself. Although it may still be a useful shorthand to speak of phylogenetic, architectural, and developmental constraints on phenotypic evolution, it is important to understand that such "constraints" do not constitute an alternative set of causes of evolutionary change. The result of this analysis is a clearer understanding of the relationship between adaptation, selection and constraints as explanatory concepts in evolutionary theory.

Comments

LMU users: use the following link to login and access the article via LMU databases.

Original Publication Citation

Shanahan, Timothy. "Why Don't Zebras Have Machine Guns? Adaptation, Selection, and Constraints in Evolutionary Theory," Studies in History and Philosophy of Biological and Biomedical Sciences, Volume 39, Number 1, March 2008, pp. 135-146. https://doi.org/10.1016/j.shpsc.2007.12.008

Link to Full Text

Share

COinS