The Growth of Biological Thought Revisited

Abstract

I believe that it is Mayr's criticism of cladistics and defense of what has come to be known as adaptationist that causes difficulty i accepting his summary of evolutionary thought. Mayr is a primary adversary of the cladistic school of taxonomy, which became influential in the 1970s. Mayr's book details the history of various taxonomic schools but does not give a picture of the intensity of feeling that presently accompanies the espousal of cladistic taxonomy. Tattersall is an adherent of cladistics (Eldredge and Tattersall 1975; Tattersall 1982), and Mayr has always questioned the cladistic scenario of strictly dichotomous branching and concomitant extinction of the ancestral species. A further problem concerns evolutionary changes after the splitting of lineages. Mayr nd others believe that taxonomy should occasionally recognize paraphyletic groups, in order to reflect the existence of major shifts in adaptive zone. If great weight is given to derived characters acquired by one sister group and not by the other, grades or levels of evolutionary change are recognized. Recognition of such paraphyletic groups would express degree of evolutionary divergence, but would preclude a classification based on cladograms. The study of adaptive zones necessarily involves the study of the adaptations of organisms, which itself creates controversy. Some researchers have argued that the study of adaptations leads to the idea that all organisms are adaptively optimal. This Panglossian statement has been termed adaptationist by Gould and Lewontin, who believe that the study of adaptation often yields trivial research. Mayr has argued (1983) that the study of adaptations, the analysis of function, and the asking of Aristotelian why questions (of which more in the 1982 monograph) are not insignificant concerns, for they have led to many important biological discoveries. The heuristic power of the adaptationist program therefore justifies its careful use. Invention of a catch-phrase like adaptationist to describe extreme cases, and setting this up as a straw man for attack, does not necessarily mean that a traditional feature of biological study, adaptation, is extinct as a research issue.