The simple scenario many of us learned in school is that two X chromosomes make someone female, and an X and a Y chromosome make someone male. These are simplistic ways of thinking about what is scientifically very complex. Anatomy, hormones, cells, and chromosomes (not to mention personal identity convictions) are actually not usually aligned with one binary classification.
-Gasp-
This post, and the science it is based on, infuriates TERFS and Conservative bigots alike. It’s magical.
Sex biology redefined: Genes don’t indicate binary sexes – Scope
fadeslikewhispers 