I wonder how she managed to convince her doctors to help her transition. At the time, our understanding of male and female was so rudimentary. For those who believe that it is a biological fact that a person’s sex is definitively determined by their genetalia, the scientific community has been uncovering evidence that this ‘fact’ is wrong: Unfortunately, one’s physical sex is not entirely determined by just possessing a Y or an X chromosome. As a person with a BS in Biology with a focus in physiology, I would like to inform you that biologically, a person’s physical sex and brain’s gender identity are not so simple, and can easily be mismatched. Every human produces both ‘female’ and ‘male’ sex hormones in a different and unique mix (the most widely talked about hormones are Estrogen and Testosterone; testosterone actually is just an estrogen that has later been modified by another process in the body). Also, womb environment, including the mother’s hormones directly affects the formation of the child’s brain. There is actually a gradient from feminine to masculine across the human population, with two peaks at what we call Female and Male. As a common transgender example, transwomen are often people who end up with their ‘female’ hormones dominating the development of their brain, giving them a ‘female’ gender, but have male genetalia and are assigned the ‘male’ sex, or the opposite. This can occur when a child is still in the mother’s womb — some ‘boys’ will end up highly feminized if their mother produces too much of another hormone that blocks the creation of male hormones and/or produces too much estrogen. When a person with this condition has their brain structure analysed via an MRI, their brain matches the average category of physically ‘female’. The same is true for those with a male gender and female body. Having a brain that is in-between is extremely common, where both male and female hormones influenced the initial development of a child’s brain, and often leads to women who are tomboyish or skilled at math and men who are demure or gifted in communication, amongst other important parts of a person’s unique personality and skillset. Different parts of the brain may be more masculinized while others are more feminized. Additionally, there seems to be part of the brain that determines gender, and causes a person to feel that they should have a body and genetalia that don’t match what they possess, which explains the observation that most transgender individuals know that they are trans from childhood. (Similarly, there may be part of the brain that determines what genetalia a person feels sexually attracted to, which causes people to be hetero/homo/bi/pan/a-sexual) People like to organize into distinct groups, including creating simple categories of ‘male’ or ‘female’ and assigns different expectations, roles, etc. to each group. If one’s brain fits the role outlined by society for the gender category that doesn’t match their physical sex, that individual may be transgender. The nurture part of a child’s upbringing helps to reinforce a single gender identity, especially if enough of their brain fits one of the two big categories. A transgender individual can be taught to act like their genital’s sex. However transgendered people often suffer severe mental trauma because of this, which contributes to the reasons why the suicide rate for the trans population is so high.