How did Gregor Mendel’s work become part of modern evolutionary theory?

Gregor Mendel’s work became a cornerstone of modern evolutionary theory by providing the missing mechanism of inheritance that Charles Darwin’s theory of natural selection lacked.1

Initially, Darwin’s theory struggled because it relied on "blending inheritance," which would have diluted variations over generations. Mendel’s discovery of particulate inheritance—where traits are passed down as distinct units, or genes—explained how variations are preserved.12

Following the 1900 rediscovery of Mendel’s laws, early geneticists initially favored "mutationism," which challenged natural selection. However, in the 1920s and 1930s, theoretical work by geneticists such as R.A. Fisher, J.B.S. Haldane, and Sewall Wright demonstrated that Mendelian genetics could account for continuous variation and cumulative evolutionary change.3

This integration culminated in the 1937 publication of Genetics and the Origin of Species by Theodosius Dobzhansky, which effectively combined Darwinian selection with Mendelian genetics to form the synthetic theory of evolution.3