`Ah, I know that bit,' said the Lecturer in Recent Runes. `The North and South Poles are those bits on a globe where the spindle comes out. But they're invisible, of course,' he added.

`Um,' said Ponder.

`Just a minute, can we get back to these birds?' said Ridcully. `Birds with magnet heads?'

`Yes?' said Ponder, knowing that this was going to be loaded. `How?' said Ridcully, flourishing a goose leg. `On this globe, birds grew out of great big monstrous lizard beasts, isn't that so?'

`Er ... small great monstrous beasts, sir,' said Ponder, wishing not for the first time that his Archchancellor did not have a knack for remembering inconvenient details.

`Did they have to fly long distances through fog and bad weather?' said the Archchancellor.

`I doubt it, sir,' said Ponder.

'So did they already have these magnets in their heads from day one, or did they turn up by some godly hand? What does Mr Darwin of The Origin say about that?

'Not very much, sir,' said Ponder. It had been a long day.

`But it suggests, does it not, that The Ology haha, is right and The Origin is wrong. Perhaps the magnets were added when needed?' `Could be, sir,' said Ponder. Just don't let him start on the eyeball, he thought.

`I've got a question,' said Rincewind, from the end of the table. `Yes?' said Ponder, quickly.

`There's going to be monster creatures on these islands we're heading for, yes?'

`How did you know that?' said Ponder.

`It just came to me,' said Rincewind gloomily. `So there are monsters?' `Oh, yes. Giants of their kind.'

`With big teeth?'

`No, not really. They're tortoises.'

`How big?'

`About the size of an easy chair, I think.'

Rincewind looked suspicious.

`How fast?'

`I don't know. Not very fast.'

`And that's it?

'From a Darwinian perspective, the islands are famous for their many species of finches.'

`Any of them carnivorous?'

`They eat seeds.'

`So ... there's nothing dangerous where we're going?'

`No. Anyway, we don't have to go there. All we have to do now is find the point where he decides to write The Ology instead of The Origin.'

Rincewind pulled the dish of potatoes towards him. 'Sez you,' he said.

+++ I need to communicate grave news +++

The words came out of the air. In Roundworld, Hex had a voice. `We're having a bit of a celebration here,' said Ridcully. `I'm sure your news can wait, Mr Hex!'

+++ Yes. It can +++

`Good. In that case, Dean would you pass me-'

+++ I would not wish to spoil your appetite +++ Hex went on. `Glad to hear it.'

+++ The destruction of the human race can wait until after the pudding +++.

Ridcully's fork hovered between his plate and his mouth. Then he said: `Would you care to explain this, please, Mr Stibbons?'

`I can't, sir. What is happening, Hex? We completed all those tasks properly, didn't we?'

+++ Yes. But, pause for significance, have you heard of a mythical creature called a, pause again, hydra? +++

`The monster with many heads?' said Ponder. `You don't need to tell us when you pause, by the way.'

+++ Thank you. Yes. Cut off one head and a dozen grow in its place. This history is a hydra +++

Rincewind nodded at Ponder. `Told you,' he said, with his mouth full.

+++ I am unable to explain why this is the case, but there are now 1457 reasons why Darwin did not write The Origin of Species. The book has never been written in this history. The voyage has never taken place +++

`Don't be silly! We know it did!' said the Dean.

+++ Yes. It did. But now, it hasn't. Charles Darwin the scientist has been removed from this history while you ate. He was, and now he was not. He became a little-remembered priest who caught butterflies. He wrote no book. The human race dies in five hundred years +++

`But yesterday-' Ridcully began.

+++ Consider time not as a continuous process but as a succession of discrete events. Darwin's scientific career has been excised. You remember him, but that is because you are not part of this universe. To deny this is simply to scream at the monkeys in the next tree +++

`Who did it?' said Rincewind.

`What sort of question is that?' said Ponder. `No one did it. There isn't anyone to do things. This is some kind of strange phenomenon.'

+++ No. The act shows intelligence +++ said Hex. +++ Remember, I detected malignity. I surmise that your interference in this history has led to some counter-measure +++

`Elves again?' said Ridcully.

+++ No. They are not clever enough. I can detect nothing except natural forces +++

`Natural forces aren't animate,' said Ponder. `They can't think!' +++ pause for dramatic effect ... Perhaps the ones here have learned to +++ said Hex.

WATCH-22

IN THE STANDARD VERSION OF Roundworld history, Charles Darwin's presence on the Beagle came about only because of a highly improbable series of coincidences - so improbable that it is tempting to view them as wizardly intervention. What Darwin expected to become was not a globetrotting naturalist who revolutionised humanity's view of living creatures, but a country vicar.

And it was all Paley's fault.

Natural Theologys seductive and beautifully argued line of reasoning found considerable favour with the devout people of Georgian (III and IV) England, and after them, the equally devout subjects of William IV and Victoria. By the time Victoria ascended to the throne, in 1837, it was indeed almost compulsory for country vicars to become experts in some local moth, or bird, or flower, and the Church actively encouraged such activities because they were continuing revelations of the glory of God. The Suffolk rector William Kirby was co-author, with the businessman William Spence, of a lavish four-volume treatise An Introduction to Entomology, for example. It was fine for a clergyman to interest himself in beetles. Or geology, a relatively new branch of science that had grabbed the young Charles Darwin's attention.

The big breakthrough in geology, which turned it into a fully fledged science, was Charles Lyell's discovery of Deep Time - the idea that the Earth is enormously older than Ussher's 6000 years. Lyell argued that the rocks that we find at the Earth's surface are the product of an ongoing sequence of physical, chemical, and biological processes. By measuring the thickness of the rock layers, and estimating the rate at which those layers can form, he deduced that the Earth must be extraordinarily ancient.

Darwin had a passion for geology, and absorbed Lyell's ideas like a sponge. However, Charles was basically rather lazy, and his father knew it. He also knew, to quote Adrian Desmond and James Moore's biography Darwin, that: The Anglican Church, fat, complacent, and corrupt, lived luxuriously on tithes and endowments, as it had for a century. Desirable parishes were routinely auctioned to the highest bidder. A fine rural `living' with a commodious rectory, a few acres to rent or farm, and perhaps a tithe barn to hold the local levy worth hundreds of pounds a year, could easily be bought as an investment by a gentleman of Dr. Darwin's means and held for his son.

That, at least, was the plan.

And at first, the plan seemed to be working. In 1828 Charles was admitted to the University of Cambridge, taking his oath of matriculation one cold January morning, swearing to uphold the university's ancient statutes and customs, `so help me God and his holy Gospels'. He was enrolled at Christ's College for a degree in theology, alongside his cousin William Darwin Fox who had started the previous year. (Charles had previously attempted medicine in Edinburgh, following in the footsteps of his father and grandfather, but he became disillusioned and left without a degree.) After getting his Batchelor of Arts degree, he might spend a further year reading theology, ready to be ordained in the, Anglican Church. He could become a curate, marry, and take up a rural position near Shrewsbury.