At my first therapy appointment way back when, we finished up and were kind of sitting there, and Martha looked at me and said with a smile, "You have small hands." I sat there with them in my lap, held up my fingers the way one might when she's admiring a ring, smiled, and said, "I know! I'm very lucky." I do have small hands for someone with my genetics. My hands are similar to my sister, who is probably 3 inches shorter than me.
I haven't spent too many brain cycles wondering what caused me to be transsexual. Even if there was a way to know, it wouldn't change anything, and at this point, I wouldn't want to change anything. Various theories abound. One of the theories is a lack of exposure to androgens in the womb, or conversely, more exposure to estrogens in the womb. Two things account for sexually dimorphic characteristics, physical differences between the sexes. The main one is the presence of an X or Y chromosome. The second, lesser cause, is the exposure to androgens.
One such characteristic is what's known as the 2D:4D ratio, the ratio of the length of your index finger to the length of your ring finger. The ratio of these finger lengths is said to be established in the womb. A higher ratio is associated with lower androgen exposure; a lower ratio is associated with more exposure to androgen. There are a few examples of studies backing this association.
There was a study in Germany recently which examined the 2D:4D ratio of male-to-female transsexuals. It found that the transsexual women had a higher digit ratio than cisgender males, but similar to transgender females, pointing to a possible link between prenatal androgen exposure and MTF transsexualism. I suppose it could go something like this: A fetus had an X and a Y chromosome, but less androgen exposure in the womb, and thus developed a female gender identity.
So perhaps when I was just a mere trillion or so cells, maybe I was exposed to less androgens than was desirable, and this explains why my brain didn't quite turn out the same as my body did. Or not. This might all be a bunch of hooey. Either way, it wouldn't change anything. It is kind of interesting and fun, though. Insofar as learning why I am this way, this doesn't have much value... it's just a factoid. But in a larger sense, these sorts of studies most definitely have value. If at some point, someone was able to definitively prove a cause of transsexualism, such as a lack of exposure to androgens, perhaps it would be universally recognized as that which it is, a medical, not a psychological, condition. Someday. Probably not in my lifetime, but someday!