If something goes wrong in pregnancy, a boy baby is more likely to be born malnourished or stillborn than a girl. This may have an evolutionary basis.
How new species are created is at the core of the theory of evolution. Mammals may be a good example of how sex chromosome change drove major groups apart.
Unlike other chromosomes, the X chromosome is inactivated in nearly all cells in women – and genes on it are active in very few tissues.
What produces the differences between men and women? Are they trivial or profound? Are they genetic or environmental, or both? And are men really closer genetically to chimpanzees than to women?