Though we can't always pinpoint what causes someone to be transgender, we do know that it's often known from a very early age and those with the identity complex don't share a common experience that could be an external factor. Rather, we're finding that there can be multiple genetic causes of the condition. Some who once identified as transgender did genetic testing to discover they are intersex, a condition in which they have the chromosomes for one gender but the genitalia of another. Others are likely caused by hormonal or neurological conditions that aren't matched with the genitalia they developed in the womb.
I preface this by saying I fully support transgender rights.
People often say that people are born transsexual. I have read about things at birth correlating with being transsexual. However, there is a difference between that and being born that way. You can only say you are born that way if factors at birth account for 100% of the causation.
Consider this scenario, a biological male born in New York City grows up to be a transwoman.
Now say that same biological male was raised on an island where there are no people who are either biological female or who identify as female and there is no internet or any kind of media from outside the island that would let him know what a woman is.
Clearly he couldn't become transsexual under those circumstances. So there you go, learning about what "gender" is and what "boys" and "girls" are has to be part of the development of gender identity.
And since no two children have identical experiences in learning about any concepts one might expect that with the same inborn factors the same child under different circumstances may end up transgender in one and cisgender in the other and in some cases in the middle.
A person's gender identity is valid regardless of how it developed. I'm just pointing out that it's more likely to be a mix of nurture and nature than nature alone.
Make or female, everyone is born with a neutral brain. Only sexuality is predetermined. Seems to me that transgenders are homosexuals that can't accept who they are. And why is it that they are all "dizzy blondes" and over the top attention seekers? It's a scientific fact that all brains are gender neutral.