Population genetics
Population genetics made great progress from 1918 to 1937. During this period, Ronald Fisher, J.B.S. Haldane and Sewall Wright worked on the connection between evolution and genetics, using new mathematical techniques, such as statistical probability. E.B. Ford and Theodosius Dobzhansky did field research on the genetics of natural populations of lepidoptera and Drosophila, respectively. Broadly speaking, this work proved that the newly rediscovered Mendelian genetics could be reconciled with Darwinian evolution. This laid the groundwork for the modern evolutionary synthesis, which took place in the following years, from about 1937 to 1953.