Natural sciences (chemistry, biology, physics,) does not address the trans-gender issues; that is under the theoretical type sciences like sociology, psychology, etc.
There are also rare cases of people born with XYX, chromosomes, people born with male sex organs and female chromosomes, or a variety of other such anomalies. This is the case with all mammals; dogs, cats, bears, even humans. This is called intersex. But this anomaly is not normal any more than it is normal for people to be born with anything other than 5 fingers on each hand.Yeah; some people are born with 6 fingers, 2 fingers, 3; but nobody claims the number of fingers humans have is on a spectrum, everybody knows it is normal for humans to be born with 5 fingers; and when this does not happen, a medical doctor can examine the person and tell them exactly what went wrong and why they don’t have 5 fingers. I’m not talking about this; I’m talking about people who are not intersex claiming they are something other than what their biology say they are.