No category of anything is absolute, if you want to be an utter perfectionist. How can we be sure anyone is REALLY a human, or a mammal, or alive, or an adult, or mentally competent... Some of them have looser edges than others, but we live in a real world, not an ideal one, so even though children can understand the difference between a man and a woman, between a dog and a cat, sometimes philosophers have trouble trying to clarify the analytic definitions of exactly how we know for sure when things do or don't fit into categories.

Sex happens to be a category that's pretty reliable, though. It has a use, and both halves are needed, so it's pretty clear which side you belong to. You were born with a body that produces one or the other part of a child. Your body changes over time, but to suggest that because you have produced all of your eggs you are now no longer a woman is a bizarre misunderstanding of womanhood. You put forth about 400 eggs over the course of your life - eventually they finish but it's a journey, and your relationship to being female may shift but it doesn't mean you are now a man. YOu're a post-menopausal woman. THat's a standard part of being a woman.

I don't really know what the equivalent relation to sperm is with men, but it certainly seems like men and their penises/balls can be understood as experiencing something. Ok, some people cut things off, change things, alter their bodies: that won't change what they began with and are reacting to, ie, if they are transitioning from being male because they disliked it, then they still had a relationship to that penis that is much more intimate than someone like me who simply has no idea what it would be like to have a penis. That would mean they are a transsexual by my thinking, Male-toFemale meaning actually male, presenting as female. I am happy to recognize them as female in social scenarios as long as it doesn't interfere with legal, medical, statistical, competitive, professional or potentially dangerous or unjust situations. But basic facts remain.

If you want to call that a third sex, I think it's sort in the realm of making electric powered wheelchairs compete against track events. It's just kind of a different deal altogether - not really a "sex" anymore since it isn't reproductive, technologically enhanced and open to desires of the users, and completely unconvincing as any kind of proof that nature has more vague sex definition (or has evolved wheels...)