You must be living under a rock if you've missed out the past 140 years of debate on this subject.

There has been multiple definitions put forward, they all fall at a few (very few out of nine billion) edge cases.

I look forward to your explaination of why you feel that every human on on the planet must be assigned as either [M] or [F] at birth with no recognition of the real circumstances in the actual edge cases.

Not even the class of South African hermaphrodites cleanly all fall one way or the other.. there's furious individual by individual debate over which of the two potential gamate producing mechanisms is less mangled than the other - as you should be aware given your apparent singular obsession here.

I'm curious as to why so recently so much money has been spent on pushing Colin Wright as the new prophet of an old idea that doesn't provide a complete classification.