The cover design embodies a radiation symbol, a stylized karyotype of human chromosomes, and a genealogical table.

ISAAC ASIMOV received his academic degrees from Columbia University and is Associate Professor of Biochemistry at the Boston University School of Medicine. He is a prolific author who has written over 65 books in the past 15 years, including about 20 science fiction works, and books for children. His many excellent science books for the public cover subjects in mathematics, physics, astronomy, chemistry, and biology, such as The Genetic Code, Inside the Atom, Building Blocks of the Universe, The Living River, The New Intelligent Man’s Guide to Science, and Asimov’s Biographical Encyclopedia of Science and Technology. In 1965 Dr. Asimov received the James T. Grady Award of the American Chemical Society for his major contribution in reporting science progress to the public.

THEODOSIUS DOBZHANSKY was graduated from Kiev University and is now a professor at the Rockefeller University. He has done research in genetics and biological evolution on every continent except Antarctica. Among his distinguished published works are Radiation, Genes, and Man, Heredity and the Nature of Man, Mankind Evolving, and Evolution, Genetics, and Man. Mr. Dobzhansky received the Daniel G. Elliot Prize and Medal and the Kimber Genetics Award from the National Academy of Sciences in 1958, and the National Medal of Science awarded by the President of the United States, in 1965.