Instead of being a complementary relationship, something like a battery, where the two opposite ends are equally necessary to complete the energy circuit, the relationship between a man and a woman has always been one of subordination, in which one member of the species dominates the other. In everyday language, the word man is often used to denote all human beings. In this unbalanced relationship, man is believed to be essential, while woman is seen as the Other of man, and her status is “inessential” (to use one of Beauvoir’s terms) meaning that alone, she is not sufficient or autonomous, and that her development can only be achieved with the help of a man.
Since there is no single point in history which led to the current disparity between genders, it is not easy to comprehend the reasons for this subordination of women. Males and females are in fact nothing other than two individuals from the same species that can be defined in comparison with one another only with regards to their reproductive function, which by necessity does not depend on any hierarchy. In essence, males and females are just random variations of the same species.
In pre-agricultural societies, the differences between the two sexes were used to define each person’s role, and did involve a differentiation of tasks, but these were complementary. The division was based on physical ability, which was then crystalised and transformed into laws, moral precepts, and religious rules, which served the men as they gradually took over in the newly formed communities.
Although men and women are different biologically, those differences are functional to the continuation of the species, but are not grounds for the establishment of any hierarchy. Neither of the two functions is more important than the other because they are complementary, yet no other species has turned the biological diversity between males and females into a form of subordination.