I agree with you to a point Thorn. To me there seems to be basic core differences and the hormone levels do play a part in our temperament and behaviour. I do agree the the "nurture" angle is valid but fails as with all other things concerning humans to "splain it all", so to speak.
I read long ago about a study done on males in prisons, it show an extremely strong corelation of the males with the highest estrogen levels to be the most violent criminals. Now I am not claiming to fully understand what that means

However It does show a correlation between hormone levels and behaviours.