Natural selection
During the 1920s, a series of papers by J. B. S. Haldane applied mathematical analysis to real-world examples of natural selection, such as the evolution of industrial melanism in peppered moths. Haldane established that natural selection could work even faster than Fisher had assumed. Both workers, and others such as Dobzhansky and Wright explicitly intended to bring biology up to the philosophical standard of the physical sciences, making it firmly based in mathematical modelling, its predictions confirmed by experiment. Natural selection, once considered hopelessly unverifiable speculation about history, was becoming predictable, measurable, and testable.