Ernst Mayr has argued that Darwinian theory discredited essentialist modes of thought and replaced them with what he has called "population thinking". In this paper, I characterize essentialism as embodying a certain conception of how variation in nature is to be explained, and show how this conception was undermined by evolutionary theory. The Darwinian doctrine of evolutionary gradualism makes it impossible to say exactly where one species ends and another begins; such line-drawing problems are often taken to be the decisive (...) reason for thinking that essentialism is untenable. However, according to the view of essentialism I suggest, this familiar objection is not fatal to essentialism. It is rather the essentialist's use of what I call the natural state model for explaining variation which clashes with evolutionary theory. This model implemented the essentialist's requirement that properties of populations be defined in terms of properties of member organisms. Requiring such constituent definitions is reductionistic in spirit; additionally, evolutionary theory shows that such definitions are not available, and, moreover, that they are not needed to legitimize population-level concepts. Population thinking involves the thesis that population concepts may be legitimized by showing their connections with each other, even when they are not reducible to concepts applying at lower levels of organization. In the paper, I develop these points by describing Aristotle's ideas on the origins of biological variation; they are a classic formulation of the natural state model. I also describe how the development of statistical ideas in the 19th century involved an abandoning of the natural state model. (shrink)

This paper traces the background to R. A. Fisher's multi-factorial theory of inheritance. It is argued that the traditional account is incomplete, and that Karl Pearson's well-known pre-Fisherian objections to the theory were in fact overcome by Pearson himself. It is further argued that Pearson's stated reasons for not accepting his own achievement has to be seen as a rationalization, standing in for deeper-seated metaphysical objections to the Mendelian paradigm of a type not readily discussed in a formal scientific paper. (...) The apparent, post-Fisherian, continued acceptance of Pearson's objections is presented as an interesting problem for the historian and sociologist. (shrink)

It is evident how much Olby and Provine have contributed to a better understanding of the emergence of genetics. It is equally evident, I believe, how many obscure issues still remain to be elucidated. Indeed, their volumes have raised as many new questions as they have answered old ones. In particular, the role of constructive as well as retarding contemporary concepts in the development of new generalizations still requires far more analysis. The somewhat independent trends of various national schools and (...) the influence of neighboring fields (e.g. statistics, animal husbandry, systematics) are other areas deserving further study. All these influences contributed, one way or another, to the growth and maturation of genetics.37. (shrink)

(This insularity was further promoted by the guileless duplicity of scholars in other fields, who were all too prepared to bequeath "the problem of ...