One of the Earth School's lessons is learning to transcend a state of duality, and a soul is initiated into this lesson  when it descends into a certain body in the physical realm. The soul- which is neither masculine nor feminine- incarnates into a specific body to have certain experiences particular to that sex and gender. When a soul has experienced different bodies over many lifetimes, it begins to dis-identify with being either male or female, masculine or feminine, and begins to embody more gender expansive ways of experiencing being on Earth through an inner marriage of the expansive and contracting forces that are associated to masculine and feminine, yin and yang.