I don’t know when the big discrimination that made females inferior to males began. However, it has been put forward and more or less recognized as an actual fact for eons. It probably goes back to the Genesis Myth. You know that myth where Adam is the first ever Human.
Adam was a guy of course. We know that because God said so and because he came equipped with male genitalia which is how you can tell a male body from a female body. Then, apparently because Adam was lonely, God made Eve to be his companion.
God used one of Adam’s ribs to make Eve. Eve was a woman of course, and we know that because God said so, and because Eve had a set of genitalia different from male body.
Having been made from one of Adam's ribs, Eve was not an original like Adam. She was a sort of modified copy that Adam could use for a companion and a kind of helper. But, however it actually worked out, it is put forth very forcefully that Adam was number One, the Boss.
This of course is all mythology, but somewhere in the evolution of Human Beings, in apparently the vast majority of evolving cultures, those humans designated as male came to be accepted as superior to those designated as female. This bit of fiction came to be, if not the major, one of the most powerful influences on basically every aspect, both material and non-material of our entire existence on the planet.
This fiction generated what eventually became the slavery of woman by man. (You can call it anything you want, but it amounted to slavery.) It is absolutely necessary here to realize that the slaver is enslaved. By enslaving Woman, man enslaved himself into an extremely restricted and narrow set of behaviors as well. This fiction generated a huge veil and an enormous mountain of pseudo-facts that have become accepted as basic differences between men and women.
The real damage of this eons long lie or illusion is that it created mythical codes of behavior and expectations based on one’s genitalia. This had the effect of separating us into prisons of illusion. It literally separated the One Humanity from itself and from the One Power of Life.
Life is Energy. Energy is gender neutral. There is no energy that an incarnated soul or human being, regardless of the genitalia of its chosen body cannot embody and use. All humans can, and do, have and use Will Power, Love and Intelligence. None of these Energies is either feminine or masculine. They are all cosmic Energies and when directed by the heart or Love they manifest as kindness, gentleness, courage, indomitable Will, equilibrium, fearlessness, unshakeable confidence in Truth.
I could go on here and make a huge list; however, the point is that We are the One Humanity first, last and always.
Well not always, because there is this thing called Evolution, and that requires some discussion about another Dimension.