>>938881711
It's a fairly complex subject, so let me try to make it Barney level for you:
Human genetic variations on the 23rd pair (sex chromosomes) and SRY gene sequence complex:
XX or XY with no anomaly: 98% of all births. These are your "men" and "women".
XXX, XXXX, XXY, XXYY, XYY, XXXY, XXXXY, XO: about 2%
Birth assignment is the archaic but overly simple process of the doctor determining the infant's societal sex at birth by looking at the infant's outward genitalia. While accurate for 98% of cases, that 2% become "assigned a false sex", which can carry social stigma and difficulty in trying to force conformation on the subject.
Additionally, even rarer but still significant are those who are "Men" or "women" who have SRY shifts or SRY delays. The SRY gene sequence is what triggered the human's genitals to grow into one of the two subsets of penis/testes or vagina/ovaries. SRY can fail or be severely delayed in firing during development. When that happens, a baby born and assigned "female" at birth can then later grow a penis and testes or vice versa. This is also the scientific source of that "man in a woman's body" (and vice versa) phenomenon.
Your archaic societal model (based largely on primitive religious beliefs) wants to try to sort "male" and "female" into two distinct piles. Human growth and development simply don't conform 100% to that model. It's a failing of arrested development in modern society, not the non-conforming human who is neither man nor woman's fault.
