It is hardly surprising to find that the males best at seduction tend to be the best at other things as well; it does not prove that females are seek… - Matt Ridley

Psychologists sometimes wonder why people are endowed with the ability to learn the part of Hamlet or understand calculus when neither skill was of much use to mankind in the primitive conditions where his intellect was shaped. Einstein would probably have been as hopeless as anybody in working out how to catch a woolly rhinoceros. Nicholas Humphrey, a Cambridge psychologist, was the first to see clearly the solution to this puzzle. We use our intellects not to solve practical problems, but to outwit each other. Deceiving people, detecting deceit, understanding people’s motives, manipulating people—these are what the intellect is used for. So what matters is not how clever and crafty you are, but how much cleverer and craftier than other people. The value of intellect is infinite. Selection within the species is always going to be more important than selection between the species.

The fifth method (that is, of analyzing human mating systems) is to compare mankind with other animals that share our highly social habits: with colonial birds, monkeys, and dolphins. As we shall see, the lesson they teach is that we are designed for a system of monogamy plagued by adultery.

The cornucopia that greets you as you enter the supermarket dwarfs anything that Louis XIV ever experienced (and it is probably less likely to contain salmonella).