Chromosomes determine what chromosomes you're going to have. It is humans who decide what gender that correlates to, and even then if it's a 1 to 1 correspondance then humans get it wrong a lot of the time, for example, Turner Syndrome means that a human is born with X chromosomes. Not XX or XY, X. What are they? Jacob's Syndrome: XYY, Klinefelter Syndrome: XXY, Trisomy X, and I could go on. Not to mention every inter[WORD THAT RHYMES WITH HEX BECAUSE I KNOW BUNGIE IS GONNA CENSOR IT] person that exists that doesn't even outwardly fit into the chromosomal definition. Your "undisputed facts" are born from a naïve outlook on the world, one that peaked in high school.