Stephen J. Gould and Adaptation: San Marco 33 Years Later

Abstract

Stephen J. Gould’s concern for the wide variety of explanations for evolutionary change was one of his chief intellectual contributions. In one of his most famous papers, ‘‘The Spandrels of San Marco’’, named in honor of Venice’s own most gloried church, and which he co-authored with Richard C. Lewontin, he emphasized the importance of historical, correlational, byproduct, and phyletic evolutionary explanations, and contrasted these with adaptationist explanations. In this Article, I take a more formal approach to discussing Gould’s analysis of evolutionary explanations, now 33 years later. My analysis rests on the ‘‘logic of research questions’’, and contrasts a ‘‘methodological adaptationist’’ approach, to what I call the ‘‘evolutionary factors’’ approach. In the former, the key research question is: ‘‘What is the function of this trait?’’ while in the latter, the research question is: ‘‘what evolutionary factors account for the form and distribution of this trait?’’ I use my case study on the evolution of the female orgasm, which Gould defended in his column, and was one of his favorite examples, to illustrate how the methodological adaptationist approach can lead scientists astray. (Reports of a serious challenge to the byproduct account, based on recent poorly-designed twin studies, are unsupportable.) Biases induced by methodological adaptationism have led biologists to a failure to compare the byproduct hypothesis against an adaptive one with regard to the evidence. Perhaps, then, it is past time to take Gould’s advice, and reevaluate whether methodological adaptationism is truly as benign as it is commonly assumed to be.