For a long time I was convinced the only real difference between men and women was anatomy and up-bringing. That we were conditionally brought up to expect and act within certain norms according to gender. For me, that idea fell away once I had sons. They act like boys. They act nothing like their little girl peers. Nature is, it seems, stronger than nurture. I got to wondering how those innate differences play in the way women and men value themselves. And how that impacts inequality between the sexes.