Gregor Mendel (1822 - 1884) discovered the laws of heredity in about 1856 - 1863. Mendel went to the University of Vienna, studying Physics, Mathematics, Zoology and Botany. He became a monk, later abbot, in St Thomas's Augustinian monastery in what was then Brünn in Austria-Hungary and is now Brno in the Czech Republic. He conducted extensive experiments in plant hybridization, and propounded these results into two laws, which have become the foundation of all biology - the law of segregation and the law of independent assortment.

Nobody took much notice of Mendel's laws until 16 years after his death as an esteemed abbot but unacknowledged scientist. His laws of inheritance were immensely important for Darwin's theory, but unfortunately Darwin never came to hear of it. In the first part of the 20th century, Mendelian genetics were combined with Darwinism into what has been called neo-Darwinism, or the Modern Synthesis. The theoretical work was mainly done, independently, by R.A. Fisher, J.B.S. Haldane, and Sewall Wright.