The Rise of Chance in Evolutionary Theory

Pence, Charles H. [UCL]

Over the century from Darwin’s first theoretical notebooks to the early works of the Modern Synthesis, evolutionary theory radically transformed. A theory about the appearance of adaptations in individual organisms, worked out without the aid of mathematics and an unclear view of the probabilistic nature of natural selection, became a statistical theory of natural selection’s action on populations, which in turn needed to be harmonized with Mendelian genetics. My recently published book, The Rise of Chance in Evolutionary Theory, tells the story of this remarkable transformation. Historians of biology have long recognized a number of key moments in this history, perhaps central among them the “rediscovery of Mendel” and the so-called “biometry-Mendelism controversy,” said to have locked the field of evolutionary theory in a fruitless battle that spanned some forty years. But, I argue, this classic history obscures more than it illuminates. On the one hand, the work of these biologists was much more complicated than “Mendelian vs. biometrician” would lead us to believe. The intellectual story of the developments in conceptual frameworks, methodological tools, and even underlying philosophical commitments proves to be one of the most complex and exciting periods of innovation in the history of evolutionary theory. And on the other hand, when we analyze that story in detail, we find that a tale of continuity is better supported than one of revolution. Efforts to develop a statistical, populational theory of natural selection were present for decades and remain relevant for philosophers and historians today.