sexism

I always wonder how it was decided that women were lesser citizens than men. Did men think that women were doing most of the job in procreation so they decided to be part of the process by making the child their own, legally and socially, as a way to create more balance? And how were women convinced by it? And what about this conflicting idea that sex is taboo and sexual drive is a vulgar instinct but everything in human society is basically decided based on sex, procreation and gender, even things that have nothing to do with genitalia?