What if you have a "female" with high levels of androgens? Do you just say if you are 2 standard deviations within the mean of females you are verifiably female? Which is the cutoff?
Pick one arbitrarily. It's inelegant, sure, but we use it for all sorts of other things. Significant example: are you an adult? All sorts of perfectly intelligent, rational arguments could be raised saying "It depends on the person, now doesn't it?" The law, however, says: If you have been alive for X number of years, you are an adult. Otherwise, you are not. It seems to work halfway adequately for that.
Pick one arbitrarily. It's inelegant, sure, but we use it for all sorts of other things. Significant example: are you an adult? All sorts of perfectly intelligent, rational arguments could be raised saying "It depends on the person, now doesn't it?" The law, however, says: If you have been alive for X number of years, you are an adult. Otherwise, you are not. It seems to work halfway adequately for that.