All rules have exceptions (including this one). - Matt Ridley

The struggle for existence never gets easier. However well a species may adapt to its environment, it can never relax, because its competitors and its enemies are also adapting to their niches. Survival is a zero-sum game.

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.

Simple determinism, whether of the genetic or environmental kind, is a depressing prospect for those with a fondness for free will.