This topic is so devoid of real science and so replete with conjecture that it boggles the mind.
We haven't yet found a biological gender dysphoria marker (if such a thing exists) and that had opened the door to speculation and to charlatanism. It is, for example, what permitted Kurt Freund to mentor Ray Blanchard and ultimately create the "it's only about sex" school of transsexualism. Were it only so simple but then reality rarely is.
Thus far conjecture has managed to have the upper hand because we are not privy to the inner workings of the human brain and have barely begun to map it. It is for this reason that it was easy to treat the gender questioning patient like the man who thought he was Napoleon.
What has added weight to our credibility as transgender people (who now represent 0.6% of the population according to the latest survey data) is that most of us are hardly ready for the looney bin. When your judge, doctor or local firefighter suddenly comes out, people are hard pressed to understand but know this person through their honourable past which usually includes a credible history of integrity.
I, for example, am known in my business sphere and I am respected. Were I ever to come out fully in my field it would surprise many but I think most would try to see my decision as not being frivolous because they know me. It is this way with many others as well and it is how we will become part of the fabric of society.
This is why the pseudoscience ultimately hasn't succeeded and why transgender people are being treated favorably by the courts and governments of most nations. It is because the vast majority have a reasonable degree of credibility which carries far more weight than anything else.
Another puzzling element is that the conjecturing which is mostly present in cyberspace and within academic circles has strangely been used as ammunition for those who want to derail transgender advancement and dignity. If you are still unsure whether there is academic hubris at play ask yourself why someone so committed to this subject would turn to Twitter to denigrate the very people you are supposedly trying to assist. This is what can happen when your work starts to lose relevance.
There are many sites who purport to have the truth but couldn't be further from it and they will always attract the captive audience which agrees with them.
One day they may find actual conclusive evidence that allows us to predict whether a child will be transgender or not. But even if they don't it matters less than the idea that differences that don't harm other people should be respected for what they are: just differences.
If life experience has taught me anything it's that those who fight hardest to denigrate someone else are the ones most driven by their own fear and prejudice.