His and Hers

We tend to take evolution for granted, particularly these days when there is so much else to worry about. But, as one may say when looking back, things might have been different. Human sexual differentiation is a case in point. Granted the need for different genital anatomy in the male and female, there is no a priori reason why another solution than the familiar would not have worked. For example, female embryos could have had only the structural gene information for the development of female genitalia, and male embryos only for the male pattern. That is, the internal and external . . .