Years ago, when my kids were little, friends of ours who had vowed never to have kids use to tell us how the only reason why my daughter liked playing with dolls and my son liked playing with his tonka trucks, is because we instilled this in them by giving them these gender specific toys, rather than allowing them to make up their own mind.
Well, later it turned out that they decided to have kids and the first two were girls. They still hung onto their their genderless mentality. That is, until their son Patrick came along.
He quickly showed them that boys wanting to do boy things and girls wanting to do girl things, was a biological reality.
In fact, they wouldn't allow Patrick to have toy guns. So, one day while we're visiting, Patrick took one of the girls dolls, bent the arm down and started using the doll like it was a toy gun.
He also fashioned his tinker toys into make believe swords.
The girls never did any of these things and in fact, avoided Patrick as much as possible.
Jim