Right, pay attention at the back. You boy, straighten your tie. Now, you all know why you’ve been called back for detention with Professor Dawkins and, frankly, you’ve only got yourselves to blame. He explained it all very carefully in The Selfish Gene and The Blind Watchmaker and it even looked as if some of you were taking notes. Now I know the headmaster didn’t allow us to actually teach The God Delusion in this school, but you really should have got the gist of it. Yet your essays are full of creationist gobbledygook about the Earth being 10,000 years old and the gap in the fossil record proving there’s something suspect about this evolution lark and that Noah’s flood was literally true because it says so in the Bible.

So Professor Dawkins has very kindly agreed to stay back after school to explain it carefully, step by evolutionary step. But he does have an apology to make. He’s realised he didn’t set out the evidence for evolution as clearly as some of the fantasists and fundamentalists among you would have liked. So he is going to demonstrate that, even though we call it a theory, evolution is actually an inescapable fact. To do this, he will present evidence far more wide-ranging than just his own sphere of biology. He will, for example, call on geology to explain the age of the fossil record; on physics to interpret the half-life of radioactive isotopes; and on archaeology to put a date on human activity through the ages. If you’re going to persist with the half-cocked idea that God set the ball rolling after a six-day shift a few thousand years ago, then it’s not just Dawkins you must answer to, but the whole spectrum of modern science.

Now all of this is wearisome to Professor Dawkins, who has better things to do than fend off crackpot creationists. Besides, he’s already got The God Delusion out his system and he is even prepared to stand alongside people of faith if they, like the Bishop of Oxford, accept the principle of evolution. So rather than let himself get bogged down in a tedious squabble, he is going to demonstrate the phenomenal beauty of evolution in action, calling on the evidence of dog breeding, flower cultivation and laboratory experiments with bacteria that show that what the creationists see as ‘irreducible complexity’ is not so irreducible after all.

And because he is such a compelling communicator – always ready with an illuminating anecdote or a funny aside – this detention will be a celebration of life’s marvels and not a dry dismissal of arguments that would be laughable if they were not so pervasive. If it is not immediately apparent to you why there is no such thing as a ‘crocoduck’ sitting halfway between a crocodile and a duck in the fossil record, he will – with only a hint of exasperation – explain it with good humour. If, at the end of this detention, you are still one of those who, like 44% of Americans, believe God created human beings in the last 10,000 years, then you are merely evidence that the human race has not evolved as much as we’d like to think.

The Greatest Show on Earth is out now published by Bantam Press.