What is the X in X-mas?
Dobzhansky Dob·zhan·sky (dəb-zhān'skē), Theodosius. 1900-1975.
Russian-born American geneticist. His Genetics and the Origin of the Species (1937) synthesized Mendel's laws of heredity and Darwinian theory. He is also known for his study of the fruit fly Drosophilia, which showed a large degree of genetic variation within a population.