It is science and not a belief system anymore, like that hamster that was exposed to a pesticide with estrogen properties while he was in utero and grew up doing female hamster activities of making nests and not being sexually interested in female hamsters, basically a transgender boy hamster who felt that he was a girl hamster (but because of biology, not because of an unpopular modern hamster belief system).
It seems that scientists have found that our gender is not one single biological system but is composed of multiple systems including physical differences in our brains as well as our gonads and the systems can end up not all expressing the same gender. Some of us are all one 'flavor' and some of us are a mixture. We are all equally valid humans regardless of whether we get a mixed eye color (e.g., hazel) or a mixed gender.
As an analogy, there was a time that epilepsy was believed to involve demonic possession and 'treatment' could even include trying to torture the demon out. Then slowly science found out it was biological and if we imagine that scientific advance happening today, it would be like Massachusetts denying a foster license to a couple who believed epilepsy was demonic possession.
Whereas, in Jan 2023, another source says:
According to an international group of over 100 clinicians and researchers, there is currently no biological evidence for “gender identity” and no laboratory test that can distinguish a trans-identified person from a non-trans-identified person. Despite this, the belief in “gender identity” is used as the basis for medically transitioning
thousands of children and adolescents.
“The assumption of the core biological underpinning for ‘gender identity’ and ‘gender dysphoria’ remains an unproven theory: while biology likely plays a role in gender nonconformity, currently,
there is no brain, blood, or other objective test that distinguishes a trans-identified from a non-trans identified person once confounding factors such as sexual orientation are controlled for,” (emphasis original) said the Society for Evidence-Based Gender Medicine (SEGM) in an
article debunking false and unproven assumptions used to medically transition children.
The article addressed five myths outlined by SEGM-affiliated researcher J. Cohn in a
recent publication that critically examines and refutes the assumptions made in an influential
“pro-affirmation” paper by a prominent gender doctor. Cohn warned that when these myths and inaccuracies are perpetuated, they can be mistaken for “facts” that mislead both clinicians and patients alike. ~