Half the ideas in this book are probably wrong. - Matt Ridley

male animals have a finite sum of energy that they can spend on testosterone or immunity to disease, but not both at the same time.

What was the secret that the serpent told Eve? That she could eat a certain fruit? Pah. That was a euphemism. The fruit was carnal knowledge and everybody from Thomas Aquinas to Milton knew it.

If reproduction has been the reward and goal of power and wealth, then it is little wonder that it has also been a frequent cause and rewarding of violence.