Chromosomal variation is perfectly consistent with the existence of two and only two sexes. Crocodiles, for instance, don't have any sex chromosomes and still have two sexes! Some men have XXY--they are still male! Some fish 🐟 change sex--because they change the kind of gametes they produce! Rather than speaking to geneticists or people with political agendas, read @SwipeWright's papers (linked to in his reply), consult top evolutionary biologists. Eggs and sperm, female and male. It's just about making 👶🏽s. That's all there is to it!