Because if you give children a set of toys that includes both cars and dolls, the girls tend to play with dolls and the boys tend to play with cars. Many boys

Because if you give children a set of toys that includes both cars and dolls, the girls tend to play with dolls and the boys tend to play with cars. Many boys play with both---they use the cars to run over the dolls. And that happens even in African tribes where most people have never seen a car in their lifes, which pretty much falsifies the modern theory that all differences are due to boys wearing blue and girls wearing pink.