Since it seems to be a major misconception here
Gender is NOT dependent upon what is in one's pants. Gender is not dependent on the presence or absence of a penis, vagina, testicles, uterus, etc. It is only dependent upon how one presents oneself. Actually some transgender individuals do not want surgery or even hormones. In addition, transgender is not a new thing. It has been around for many centuries at minimum.
Straight from the APA:
Sex is assigned at birth, refers to one’s biological status as either male or female, and is associated primarily with physical attributes such as chromosomes, hormone prevalence, and external and internal anatomy. Gender refers to the socially constructed roles, behaviors, activities, and attributes that a given society considers appropriate for boys and men or girls and women. These influence the ways that people act, interact, and feel about themselves. While aspects of biological sex are similar across different cultures, aspects of gender may differ.