In the real world, there are many ways to determine sex and, as you point out, some species can actually change sex quite naturally. Humans are not one of those which is why Tyson is being silly.
However, that does not mean that it is easy to determine the sex of a human in all cases. I think you can use the obvious signs and be right about 97% of the time but the remaining 3% will still be an issue.
Firstly, not every human is either XX or XY and, secondly, some have bodies that do not match their chromosomes and that all can happen quite naturally.
"But what about clownfish?"
Human beings aren't clownfish.
"But clownfish can change sex!"
Human beings aren't clownfish.
In the real world, there are many ways to determine sex and, as you point out, some species can actually change sex quite naturally. Humans are not one of those which is why Tyson is being silly.
However, that does not mean that it is easy to determine the sex of a human in all cases. I think you can use the obvious signs and be right about 97% of the time but the remaining 3% will still be an issue.
Firstly, not every human is either XX or XY and, secondly, some have bodies that do not match their chromosomes and that all can happen quite naturally.
My best friend has XX male syndrome. So?
"Humans aren't bipedal because some people have fewer than two legs!"
We don't make general policy based on edge cases.