Terry Pratchett - The Science of Discworld I

Then he backed away hurriedly, ooking apologetic noises about the minor error in the spacetime coordinates, and knuckled off through the interstices of L-space and grabbed the first book he found that had the word 'Evolution' in the title.

The bearded man went on to write an even more amazing book. If only he had thought to use the word ' Ascent ' there might not have been all that unpleasantness.

But, there again, perhaps not.

HEX let itself absorb more of the future ... call it ... knowledge. Words were so difficult. Everything was context. There was too much to learn. It was like trying to understand a giant machine when you didn't understand a screwdriver.

Sometimes HEX thought it was picking up fragmentary instruc­tions. And, further away, much further away, there were little disjointed phrases in the soup of concepts which made sense but did not seem to be sensible. Some of them arrived unbidden.

Even as HEX pondered this, another one arrived and offered an opportunity to make $$$$ While You Sit On Your Butt!!!!! He con­sidered this unlikely.

The title brought back by the Librarian was The Young Person's Guide to Evolution.

The Archchancellor turned the pages carefully. They were well illustrated. The Librarian knew his wizards.

'And this is a good book on evolution?' said the Archchancellor.

'Ook.'

'Well, it makes no sense to me,' said the Archchancellor. 'I mean t'say, what the hell is this picture all about?'

It showed, on the left, a rather hunched-up, ape-like figure. As it crossed the page, it gradually arose and grew considerably less hairy until it was striding confidently towards the edge of the page, per­haps pleased that it had essayed this perilous journey without at any time showing its genitals.

'Looks like me when I'm getting up in the mornings,' said the Dean, who was reading over his shoulder.

'Where'd the hair go?' Ridcully demanded.

'Well, some people shave,' said the Dean.

'This is a very strange book,' said Ridcully, looking accusingly at the Librarian, who kept quiet because in fact he was a little worried. He rather suspected he might have altered history, or at least a his­tory, and on his flight back to the safety of UU he'd seized the first book that looked as though it might be suitable for people with a very high IQ but a mental age of about ten. It had been in an empty byway, far off his usual planes of exploration, and there had been very small red chairs in it.

'Oh, I get it. This is a fairy story,' said Ridcully. 'Frogs turnin' into princes, that kind of thing. See here ... there's something like our blobs, and then these fishes, and then it's a ... a newt, and then it's a big dragony type of thing and, hah, then it's a mouse, then here's an ape, and then it's a man. This sort of thing happens all the time out in the really rural areas, you know, where some of the witches can be quite vindictive.'

'The Omnians believe something like this, you know,' said the Senior Wrangler. 'Om started off making simple things like snakes, they say, and worked his way up to Man.'

'As if life was like modelling clay?' said Ridcully, who was not a patient man with religion. 'You start out with simple things and then progress to elephants and birds which don't stand up properly when you put them down? We've met the God of Evolution, gentle­men ... remember? Natural evolution merely improves a species. It can't change anything.'

His finger stabbed at the next page in the brightly coloured book.

'Gentlemen, this is merely some sort of book of magic, possibly about the Morphic Bounce Hypothesis [37] ... which had engrossed wizards for many years. The debate ran like this: it was quite easy to turn someone into a frog, and fairly easy to turn them into, say, a white mouse. Strangely, considering the basic similarity of size and shape, turning someone into an orangutan took a vast amount of power and it was only an explosion in the intense thaumic confines of the Library which had managed the trick. Turning someone into a tree was much, much harder even than that, although turning a pumpkin into a coach was so easy that even a crazy old woman with a wand could do it. Was there some kind of framework into which all this fitted? The current hypothesis was that most Change spells unravelled the vic­tim's morphic field down to some very basic level and then 'bounced' them back. A frog was quite simple, so they wouldn't have to bounce far. An ape, being quite human-like in many respects, would mean a very long return jour­ney indeed. You couldn't turn someone into a tree because there was no way to get there from here, but a pumpkin could be turned into a wooden coach because it was quite close to it in vegetable space. The wizards agreed that this all seemed to fit nicely, and was therefore true. If William of Occam had been a wizard at Unseen University, he would have grown a beard. . Look at this.' The picture showed a very large lizard followed by a big red arrow, followed by a bird. 'Lizards don't turn into birds. If they did, why have we still got lizards? Things can't decide for themselves what shape they're going to be. Ain't that so, Bursar?'

The Bursar nodded happily. He was halfway through HEX's write-out of the theoretical physics of the project universe and, so far, had understood every word. He was particular happy with the limitations of light speed. It made absolute sense.

He took a crayon and wrote in the margin: 'Assuming the uni­verse to be a negatively curved non-Paramidean manifold, which is more or less obvious, you could deduce its topology by observing the same galaxies in several different directions.' He thought for a moment, and added: 'Some travel will be involved.'

Of course, he was a natural mathematician, and one thing a nat­ural mathematician wants to do is get away from actual damn sums as quickly as possible and slide into those bright sunny uplands where everything is explained by letters in a foreign alphabet, and no one shouts very much. This was even better than that. The hard-to-digest idea that there were dozens of dimensions rolled up where you couldn't see them was sheer jelly and ice cream to a man who saw lots of things no one else saw.

THE WIZARDS MET THE GOD OF EVOLUTION in The Last Continent. He made things the way a god ought to:

"'Amazin' piece of work," said Ridcully, emerging from the elephant. "Very good wheels. You paint these bits before assembly, do you?"'

The God of Evolution builds creatures piece by piece, like a butcher in reverse. He likes worms and snakes because they're very easy, you can roll them out like a child with modelling clay. But once the God of Evolution has made a species, can it change? It does on Discworld, because the God runs around making hurried adjustments... but how does it work without such divine interven­tion?

All societies that have domestic animals, be they hunting dogs or edible pigs, know that living creatures can undergo gradual changes in form from one generation to the next. Human intervention, in the form of 'unnatural selection', can breed long thin dogs to go down holes and big fat pigs that provide more bacon per trotter [38] The quantity of bacon per trotter is on average slightly more than one quar­ter of the amount per head. . The wizards know this, and so did the Victorians. Until the nine­teenth century, though, nobody seems to have realized that a very similar process might explain the remarkable diversity of life on Earth, from bacteria to bactrians, from oranges to orangutans.

They didn't appreciate that possibility for two reasons. When you bred dogs, what you got was a different kind of dog, not a banana or a fish. And breeding animals was the purest kind of magic: if a human being wanted a long thin dog, and if they started from short fat ones, and if they knew how the trick worked (if, so to speak, they cast the right 'spells') then they would get a long thin dog. Bananas, long and thin though they might be, were not a good starting point. Organisms couldn't change species, and they only changed form within their own species because people wanted them to.