Science of Discworld

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. 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 su

THE DESCENT OF DARWIN

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 'u

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.

Around 1850, two people independently began to wonder whether nature might play a similar game, but on a much longer timescale and in a much grander ma

What was the initial reaction to these two Earth-shattering arti­cles? In his a

This is the idea. You don't need a human being to push animals into new forms; they can do it to themselves, more precisely: to each other. This was the mechanism of natural selection. Herbert Spencer, who did the important journalistic job of interpreting Darwin's theory to the masses, coined the phrase, 'survival of the fittest' to describe it. The phrase had the advantage of convincing everybody that they understood what Darwin was saying, and it had the disadvantage of convincing everybody that they understood what Darwin was saying. It was a classic lie-to-children, and it deceives many critics of evolution to this day, causing them to aim at a long-disowned target, besides giving a spurious 'scientific' background to some extremely stupid and unpleasant political the­ories.

Starting from an enormous range of observations of many species of plants and animals, Darwin had become convinced that organisms could change of their own accord, so much so that they could even, over very long periods, change so much that they gave rise to new species.

Imagine a lot of creatures of the same species. They are in com­petition for resources, such as food, competing with each other, and with animals of other species. Now suppose that by random chance, one or more of these animals has offspring that are better at wi