We have known for a long time that the organization of any particular society is influenced by the definition of the sexes and the distinctions drawn between them. (1) {{U}}But we have realized only recently that the identity of each sex is not so easy to pin down, and that definitions evolve in accordance with the different types of culture known to us scientific discoveries, and ideological revolutions{{/U}}. Our nature is not considered immutable, either socially or biologically.As we approach the end of the century, the substantial progress made in biology and genetics is radically changing the roles, responsibilities, and specific characteristics attributed to each sex; and yet, scarcely twenty years ago, these were thought to be "beyond dispute." We can safely say, yam a few minor exceptions, that the definition of the sexes and their respective functions remained unchanged in the West from the beginning of the nineteenth century to the 1960s. (2){{U}}The role distinction, raised in some cases to the Status of uncompromising dualism on a strongly hierarchical model, lasted throughout this period, appealing for its justification to nature, religion, and customs alleged to have existed since the dawn of time.{{/U}} The woman bore children and took care of the home. The man set out to conquer the world and was responsible for the survival of his family, by satisfying their needs in peace time and by going to war when necessary. (3) {{U}}The entire world order rested on the divergence of the sexes.Any overlapping or confusion between the roles was seen as a threat to the time-honored order of things. It was felt to be against nature, a deviation from the norm.(4) {{U}}The dawn of the third millennium is coinciding with an extraordinary reversal in the power structure.{{/U}} (5) {{U}}Not only will the patriarchal system be dead and buried in most of the industrialized West, but we shall see the birth of a new imbalance in the relations between the sexes, this time exclusively to women’s advantage.{{/U}}{{/U}}