You need to understand how human beings bring together their brains and enable their ideas to combine and recombine, to meet and, indeed, to mate. In other words, you need to understand how ideas have sex.

The interaction of genetic and external influences makes my behaviour unpredictable, but not undetermined. In the gap between those words lies freedom.

Ecology, like genetics, is not about equilibrium states. It is about change, change and change. Nothing stays the same forever.

Because it is a monopoly, government brings inefficiency and stagnation to most things it runs; government agencies pursue the inflation of their budgets rather than the service of their customers; pressure groups form an unholy alliance with agencies to extract more money from taxpayers for their members. Yet despite all this, most clever people still call for government to run more things and assume that if it did so, it would somehow be more perfect, more selfless, next time.

Trade is 10 times as old as farming.

How much more generous it would be if, instead of writing parables about childhood wounds, psychologists were to accept that some differences between the sexes just are, that they are in the nature of the beasts, because each sex has an evolved tendency to develop that way in response to experience.

Every minute, every second, the pattern of genes being expressed in your brain changes, often in direct or indirect response to events outside the body. Genes are the mechanisms of experience.