Question #798: How do we know we're always the same gender?

[Ask Satya Operator]

So through reincarnation I think it's believed here that we are always reincarnated into the same gender so a girl will always be a girl and a boy will always be a boy. How do we know this to be true and that we don't switch genders every few lifetimes? What evidence is there for this? What determines staying the same gender and for what purpose? If that's true then what is up with transgenders and gay/lesbian/bisexual souls? Pure curiosity no offense towards anyone.