What do we need two sexes for? What is the evolutionary significance of this phenomenon? What is the nature of the differences between the sexes? What is sexual dimorphism and what does it mean? How is it connected to other life phenomena? The new evolutionary theory of sex differentiation developed by Dr. of Biological Sciences Vigen A. Geodakyan has the answers. It provides a scientific justification for the existence of men and women, and the evolutionary roles that they play in family and society.