I got this question over at tumblr:
Is it possible for your gender to really Change?
Like instead of just unlocking your true identity (an oversimplification), is it possible for your gender identity to have shifted over time instead of just having been the One True Gender (or lack of gender) the whole time?
Here's my response:
There is much that is unknown about how gender identities are formed. The current scientific consensus seems to be that a stable gender identity appears relatively early in life, at around 3 years old at the latest, and that it is caused by an interplay between different factors.
Genes play a part, but there is no single “gender identity gene”. Many genes are involved in the development of both biological sex and the experience of “being gendered”.
Studies of identical twins show that if one is transgender, the chances of the other one being trans too, is much higher than pure chance would allow for. But there are a lot of cases where one is cis and another is trans, which tells me that although genes are part of the explanation, they do not tell the whole story.
Hormones seem to play an important part, especially in the womb, where the production of hormones and the cells’ ability to “read” these hormones, influence the development of both body and brain.
Your own personal life story definitely shape the way you understand your own gender identity. Culture and the social dynamics are therefore also important factors.