"31. Just So
"'There is not a single piece of human behaviour that cannot be explained in terms of our history as evolved beings,' Dr. Kipling told his rapt audience. 'Perhaps someone would like to test this hypothesis?'

"A hand flew up. 'Why do kids today wear their baseball caps the wrong way round?' asked someone wearing his peak-forward.

"'Two reasons,' said Kipling, confidently and without pause. 'First, you need to ask yourself what signals a male needs to transmit to a potential mate in order to advertise his suitability as a source of strong genetic material, more likely to survive than that of his competitor males. One answer is brute physical strength. Now, consider the baseball cap. Worn in the traditional style it offers protection against the sun and alsothe gaze of aggressive competitors. By turning the cap around, the male is signalling that he doesn't need this protection; he is tough enoug to face the elements and the gaze of any who might threaten him.

"'Second, inverting the cap is a gesture of non-conformity. Primates live in highly ordered social structures. Playing by the rules is considered essential. Turning the cap around shows that the male is above the rules that constrain his competitors and again signals that he has superior strength.

"'Next?'"