Disentangling those factors would be exceedingly difficult, although longitudinal cross-cultural studies (possibly widely separated twins) might get you somewhere.
Animal model populations' medical institutional bias is somewhat lower.
There aren't just the social factors with coming out, but also the education around being being trans. Some people live their entire lives not knowing and only find out after watching youtube, meeting people in the community, or going to therapy (which is also becoming more commonplace and acceptable). The stigma attached to trans people as mentally unwell 'others' prevented people from even considering it for most of their lives.
Also, I do not believe there is an unbalance of trans woman to trans men. Trans women are more controversial (bathrooms) than trans men, which puts them in a public spotlight. Trans women often present themselves as stereotypical women, and if they've not fully medically/surgically transitioned yet, it makes them easy to pick out in a crowd. Trans men, on the other hand, wear men's clothes, which happen to be gender neutral if worn casually. They are often seen as 'butch' women if not fully transitioned, not trans men. You oftentimes probably wouldn't notice or identify trans men when you see them.
Disclaimer: I'm a trans woman.
So much of our identity is special to us. How would you feel as a gay man if someone told you that the reason your sexuality was not standard heterosexual was because your mum's womb was knackered from having seven kids and you were last in the line?
This is a thing, but, after spending a teenage coming out, it is just a bit of a harsh thing to be told.
Since we can't even discuss this yet, what chance is there that we will have the conversation about how pollution is messing up our fertility and gender?
Trans people were known in ancient Greece ffs, it's mostly thanks to the Catholic church and its "morals" that we ended up with imprisoning people for being gay or trans.
And I never said they didn’t exist, so I’m not sure why you seem to have an aggressive tone. I know they’ve always existed. But with research showing intersex births becoming more common than ever, I have to wonder if there’s a connection to rates of being trans as well.
That said, I think it's worth investigating. Here's a paper from Scott Kerlin, showing the results of survey from DES sons. It's a group of people born as male to women given DES, an estrogen affecting drug.
http://worldaa1.miniserver.com/~gires/assets/Research-Assets...
"More than 150 network members with “confirmed” or “strongly suspected” prenatal DES exposure status indicated they are either transsexual (pre- or post-operative, 90 members), transgender (48 members), “gender dysphoric” (17 members), or intersex (3 members)."
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A strong caveat to this would be that people don't just join a group called DES sons on a whim. A large number of women were given DES. Many more than 500 sons were born to them. People who joined the group are self selecting as having had some sort of problem or concern to discuss.
And that's almost all I could find on the topic. The only other thing that seemed notable is that the brains of transgender people resemble those of their chosen sex, not their birth sex. I.e. a MTF person had a brain typical of a women, not a man. But, this difference may only appear in adulthood, so it isn't clear if it is physiological or social.
If someone wanted to investigate this, investigating the testicular and endocrinal health of MTF people before transition would be a good start. If endocrine disruption had anything to do with it you would expect to see much more testicular cancer. The DES group had 5 out of 500 with this cancer, incidentally, while having a low cancer incidence overall.
I would categorize the published research on this topic as extremely slim. It's not even at the hypothesis stage, and your question isn't answerable without much further research.
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Oh also, while traditionally there were more MTF, recently gender dysphoria clinics are reporting more FTM.
Here are some numbers from the UK: http://gids.nhs.uk/number-referrals
The year on year referral increase is very large. So social acceptance/awareness must have a sizeable role. Endocrine dysruption can't explain a ~4x increase in 5 years.
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Edit: I should have included this: https://en.m.wikipedia.org/wiki/Causes_of_transsexuality
Doesn't touch on endocrine disruption in terms of estrogen exposure though.
I haven't researched it further, but I heard a theory that female hormonal contraception is a contributor to people identifying as LGBT.