The most elementary error that people make in interpreting the effects of genes versus those of the environment is to assume that you can truly separate one from the other. Donald Hebb, the brilliant Canadian neuropsychologist, when asked whether nature or nurture contribute more to human personality, reportedly said, "Which contributes more to the area of a rectangle, its length or its width?"

This was a clever reply, but unfortunately only reinforced the highly misleading idea that genetics and environment are orthogonal concepts, like Newtonian space and time. In fact they're more like Einsteinian spacetime: deeply intertwined and with complex interactions that can give rise to counterintuitive results.

Of course, the experts already know this. They realise, for example, that most children inherit from their parents not only genes but also their environment.