“Sexual differentiation begins approximately six weeks after conception, when in male children the gonads are formed and begin to manufacture male hormone, which has a profound effect on the future development of the embryo. In the female, on the other hand, the ovaries are not formed until the sixth month, by which time the greater size, weight, and muscular strength of the male is already established. This is the biological basis of the sexual dimorphism apparent in the great majority of societies known to anthropology, where child-rearing is almost invariably the responsibility of women, and hunting and warfare the responsibility of men. These differences have less to do with cultural `stereotypes' than some fashionable contemporary notions would have us believe. While it is true that at all ages males and females have far more in common than they have differences between them, there can be no doubt that some differences exist which have their roots in the biology of our species. Jung was quite clear about this. Again and again, he refers to the masculine and the feminine as two great archetypal principles, coexisting as equal and complementary parts of a balanced cosmic system, as expressed in the interplay of yin and yang in Taoist philosophy. These archetypal principles provide the foundations on which masculine and feminine stereotypes begin to do their work, providing an awareness of gender. Gender is the psychic recognition and social expression of the sex to which nature has assigned us, and a child's awareness of its gender is established by as early as eighteen months of age.”