Like so many of us, I felt something was different about me as a very young age, and I remember push-back from my family, encouraging me to be more like a boy, even though I don’t recall exactly what I might have been doing/how my behavior might have seemed inappropriate. So, from a causal perspective, I have to assume that some genetic or developmental factors influenced the development of my gender before birth.
There are few outward signs…other than I have never been particularly hairy and despite overcompensating by trying to build my musculature, hours in the gym and intense weight training simply didn’t pan out. I got fit, but not really “big”
So, perhaps in the case of people like me, who began life with an awareness of non-conforming gender, we were born this way. That’s not to say that others couldn’t arrive at this point by other avenues, but one would always be left wondering if their evolution wasn’t rooted in biologically pre-ordained characteristics.