Intelligent life on a planet comes of age when it first works out the reason for its own existence. If superior creatures from space ever visit earth, the first question they will ask, in order to assess the level of our civilization, is: ‘Have they discovered evolution yet?’ Living organisms had existed on earth, without ever knowing why, for over three thousand million years before the truth finally dawned on one of them.

Richard Dawkins, The Selfish Gene, 2nd ed., Oxford, 1989, p. 1