This is important to clarify because the genderqueer brigade will always bring up intersex ppl and XXYs and whatnot, but a proper understanding of biological sex blows all that shit up.
There do exist irregular sets of chromosomes and irregular genitalia, but there is no gamete other than eggs and sperm, so such irregularities do not serve any kind of nonbinary reproductive function.
Elon Musk says he WON'T get a coronavirus vaccine because he's 'not at risk' and says the pandemic has 'questioned my faith in humanity' because people have become 'irrational'