Theodosius Dobzhansky's work in genetics and evolutionary biology ensures his recognition as an influential scientist of the twentieth century. The recipient of the 1964 Medal of Science, his most significant contributions were in the development of the modern theory of evolution. His first book on evolutionary theory, Genetics and the Origin of Species, is considered by many scientists to be the most important book on the subject to be written in the twentieth century. In it, Dobzhansky was able to link the work of Austrian botanist Gregor Mendel and English naturalist Charles Darwin. He accomplished this by gathering empirical evidence that supported Mendel's mathematical theories of inherited traits, while extending critical evolutionary issues far beyond the mathematical model.

A common thread of biological evolution runs through his enormous output of written work--nearly six hundred publications, including twelve books--spanning biological, philosophical, and humanistic disciplines. Dobzhansky's gifts as an original thinker...