Biology IS what determines how many genders there are...TWO, then there are Hermaphrodites, which are rare. THAT IS IT, NO MORE! I am so sick of being told I assumed someone's gender. So, now I just ask if I can't tell. So, WHAT are you?! According to grammar and etiquette, IF you do not know if someone is a man or woman, you just PRESUME that person is a MAN until corrected or confirmed. That is English Grammar and Traditional Etiquette.