In 1900, the average American spent $76 of every $100 on food, clothing and shelter. Today he spends $37. - Matt Ridley

There is, therefore, such a thing as a universal human nature, common to all people.

This means—and religious people might find this a useful argument—that there was only one creation, one single event when life was born. Of course, that life might have been born on a different planet and seeded here by spacecraft, or there might even have been thousands of kinds of life at first, but only Luca survived in the ruthless free-for-all of the primeval soup. But until the genetic code was cracked in the 1960s, we did not know what we now know: that all life is one; seaweed is your distant cousin and anthrax one of your advanced relatives. The unity of life is an empirical fact. Erasmus Darwin was outrageously close to the mark: ‘One and the same kind of living filaments has been the cause of all organic life.’

The genome is littered, one might almost say clogged, with the equivalent of computer viruses, selfish, parasitic stretches of letters which exist for the pure and simple reason that they are good at getting themselves duplicated. We are full of digital chain letters and warnings about marmalade.