I believe the problem is never showing evidence, but that the evidence is overwhelming. I could explain the general idea and, maybe, one or two specifics. People that use the XX/XY binary argument wouldn’t be able to explain either, but it’s usually only used because it conforms to a bias. And we are only talking about humans here. Language would implode if we tried to maintain convenient binaries and still back it up with science.
Sex is not a social construct. Gender is.
It’s true - we are learning more about sex every year and understanding it’s not completely binary. But your sex is assigned at conception.
That’s one of the reasons doctor’s don’t ask about your gender, but your sex - because treating could be different. And, as an example, IHE (medical standard) recognizes about 7 sexes.
Gender, on the other hand, defines social norms we expect from certain sex. How gender is perceived changes from culture to culture and from one period of history to another - sex doesn’t.
That being said, I do believe that gender roles should be a thing of the past. You do you, whatever you’re comfortable with.