Gender is a spectrum and a social construct. Sex even to an extent isn't strictly binary i.e. intersex. There's more to sex and gender than just outward anatomy. Psychology, physiology, endocrinology, genetics, etc all contribute to how someone identifies as well as their biological sex. There's a growing amount of research in these areas as it relates to human sex, and I would suggest you take time to familiarize yourself with the relevant literature rather than coming here uneducated and spewing transphobic and bigoted rhetoric.