Nicola Bertoldi

The development of a biological notion of “population” over the first century of the theory of evolution has been commented upon by a number of historians and philosophers of biology. Somewhat less commonly discussed, however, is the parallel development of the statistical concept of a population over precisely the same period, in some cases driven by the same historical actors (such as Francis Galton and R. A. Fisher). We explore here these parallel developments, first from the perspective of a reconstruction of the historical development of each concept, then with the aid of a digital analysis of a corpus of literature drawn from the journals Biometrika and Journal of Genetics, between 1900 and 1960. These twin analyses show both points of interesting overlap between these two historical trends as well as points of important divergence. The biological and statistical notions of “population” seem to be relatively clearly distinguishable over these six decades, in spite of the fact that a number of authors contributed clearly to both traditions. The complex interplay of continuity and discontinuity across these two notions of “population” makes them a particularly interesting case study of scientific conceptual change.

La théorie de Darwin est considérée par de nombreux historiens comme une véritable révolution scientifique, raison pour laquelle l’objectif de cet article est précisément de rendre compte des caractères révolutionnaires de cette théorie, dans le cadre d’une conception des révolutions scientifiques empruntée à l’œuvre de Thomas Kuhn. Cela implique, notamment, la définition d’un « paradigme darwinien », à la fois comme matrice disciplinaire et comme solution exemplaire à un problème donné. Dans un tel but, nous définirons la structure et le contenu de la théorie de Darwin, afin de mettre au jour la problématique qui pourrait être à la base d’un « paradigme darwinien », c’est-à-dire le problème de la complexité adaptative du vivant. Nous identifierons ensuite ce qui distinguerait ce paradigme des autres, si bien que le problème de la complexité ne saurait être posé et résolu que dans son cadre. Pour ce faire, nous nous concentrerons sur deux dichotomies : d’une part, celle entre fonctionnalisme et formalisme, d’autre part, celle entre naturalisme et idéalisme. En conclusion, nous mettrons au jour les limites de l’épistémologie kuhnienne pour l’analyse de la théorie de l’évolution, ce qui nous amènera à equisser les contours d’une approche alternative, que nous appellerons « ontologie historique ».

This paper contributes to the ongoing reassessment of the controversy between William Bateson and Karl Pearson by characterising what we call “Batesonian Mendelism” and “Pearsonian biometry” as coherent and competing scientific outlooks. Contrary to the thesis that such a controversy stemmed from diverging theoretical commitments on the nature of heredity and evolution, we argue that Pearson’s and Bateson’s alternative views on those processes ultimately relied on different appraisals of the methodological value of the statistical apparatus developed by Francis Galton. Accordingly, we contend that Bateson’s belief in the primacy of cross-breeding experiments over statistical analysis constituted a minimal methodological unifying condition ensuring the internal coherence of Batesonian Mendelism. Moreover, this same belief implied a view of the study of heredity and evolution as an experimental endeavour and a conception of heredity and evolution as fundamentally discontinuous processes. Similarly, we identify a minimal methodological unifying condition for Pearsonian biometry, which we characterise as the view that experimental methods had to be subordinate to statistical analysis, according to methodological standards set by biometrical research. This other methodological commitment entailed conceiving the study of heredity and evolution as subsumable under biometry and primed Pearson to regard discontinuous hereditary and evolutionary processes as exceptions to a statistical norm. Finally, we conclude that Batesonian Mendelism and Pearsonian biometry represented two potential versions of a single genetics-based evolutionary synthesis since the methodological principles and the phenomena that played a central role in the former were also acknowledged by the latter—albeit as fringe cases—and conversely.