R.A. Fisher

Ronald Aylmer Fisher (1890–1962) was a British statistician, evolutionary biologist, and geneticist whose mathematical formalization of natural selection established the theoretical foundation for the Modern Synthesis. His 1930 treatise The Genetical Theory of Natural Selection demonstrated that Mendelian inheritance was compatible with continuous variation and gradual evolution, resolving the apparent conflict between genetics and Darwinism. Fisher developed analysis of variance (ANOVA), maximum likelihood estimation, and the concept of Fisher information, making him one of the founders of modern statistics.

Fisher's evolutionary theory assumed infinite populations and deterministic selection, minimizing the role of genetic drift. This put him in direct conflict with Sewall Wright, who argued that real populations are finite and subdivided, and that drift plays a creative role in evolution. The Fisher-Wright debate defined population genetics for half a century. Fisher had the mathematics; Wright had the biology. Both were right, but about different questions.