The evolutionary implication is that we are descended from a common ancestor with flies which used the same way of defining the pattern of the embryo… - Matt Ridley

We give boys tractors and girls dolls. We are reinforcing the stereotypical obsessions that they already have, but we are not creating them.
This is something every parent knows. Despairingly they watch their son turns every stick into a sword or gun, while their daughter cuddles even the most inanimate object as if it were a doll.

The genome is littered, one might almost say clogged, with the equivalent of computer viruses, selfish, parasitic stretches of letters which exist for the pure and simple reason that they are good at getting themselves duplicated. We are full of digital chain letters and warnings about marmalade.

Humanity shares this profile of ardent, polygamist males and coy, faithful females with about 99 percent of all animal species, including our closest relatives, the apes.