There is no question that physical and mental strength can produce great results. But why are women so much the opposite of man? - why so much the "opposite sex"? Surely physical and mental strength in women would have done no harm?
A bipolarization of personality types would aid pair-bonding, breeding, and child nurturing, by making men and women psychologically dependent on each other. A couple would grow to need each other to complement and fulfill their individual personalities. Woman grew to need man not only for his physical and mental strength, not only for his support and sex, but also to help in exercising the male part of her own personality. Similarly, man grew to need woman not only for her body and her particular mental skills, butr also to exercise and satisfy the female part of his personality.
In addition, the segregation of personality types into well defined roles simplifies social interactions. People could then specialize in certain tasks, and thereby achieve greater things. Everyone would know what was expected of them, and how to behave towards others, which would undoubtedly reduce stress in society and perhaps increase its efficiency.