[wanorris]

And yet there are plenty of kids who are gender atypical, sometimes in a few ways, sometimes in many ways, sometimes such that they identify with the opposite gender.

The reality is not that there are hard categories of things that we can simply say a person's brain is "hard wired" to be either A or B, but that there are clusters and statistical probabilities. Some people are one or more standard deviations removed from what we think of as "gender typical."

There's definitely an element of truth to the "hard wiring" thing -- you can't change a child's personality and enthusiasms simply by wishing it so or trying to "train" them. But the picture is far more complicated than you seem to think.

[einhverfr]

I am not sure that "gender" (as opposed to 'sex') is a biological state, though. Gender-atypicality may have a lot to do with navigating between social ideals of normality and a need of individuality.