The Science of Discworld II

by Terry Pratchett

  The Biblical stories don’t mention those.6

  1 There’s been a very cute discovery about elephants recently, and the only place we can find to put it is this footnote. (This, after all, is what footnotes are for.) It has been known since 1682 that elephants’ lungs are unusual, without the ‘pleural cavity’, a space between the lungs and the chest wall that is filled with fluid, that most mammals have. Instead of fluid, elephants’ lungs are surrounded by loose connective tissue. It now looks as if this type of lung exists because it lets elephants go snorkelling, breathing through their trunks. In 2001 the physiologist John West calculated that with a normal pleural cavity, the pressure of the water would burst the tiny blood vessels in the pleural membrane and snorkelling could be fatal. We’re now wondering whether the trunk evolved in the ocean as a snorkel. Land vertebrates first evolved from fish that came up on to the seashore. Much later, a variety of mammals went back into the oceans and evolved into several kinds of sea-mammals, the most spectacular modern descendants being whales. We now see that somewhere along the way, some of those water-adapted mammals came back on to the land and turned into elephants. So the elephant is now on its second evolutionary journey out of the water and on to the land. It would be nice if it made up its mind.

  2 See The Science of Discworld, chapter 38.

  3 Peasants do cost.

  4 David Brin fans will know what we mean here: in the Five Galaxies, no race (save for the long-defunct Progenitors) ever became extelligent without the aid of a sponsor race which already was. Save for humans, because even in an SF story we need to feel superior. We are, after all, the True Human Beings.

  5 Always be careful of the twentieth-century ‘story’ of ‘the natives who live in harmony with their environment’. It tends to gloss over the fact that back in history they killed off all the really big animals, and now it’s a choice between harmony and death.

  6 Mind you, Genesis does say that after Cain killed Abel he was exiled to the land of Nod, on the east of Eden, where he ‘knew his wife’ and Enoch was born. It doesn’t tell us how the wife got to Nod in order to be known. She could have been one of those unmentioned servants, slaves or concubines. That, in turn, raises even more problems with the story of Adam and Eve.

  ELEVEN

  THE SHELLFISH SCENE

  THE WIZARDS WATCHED CAREFULLY.

  ‘There’s five of them sitting there with him now,’ said Ponder. ‘And some children. He seems to be getting on well enough.’

  ‘They’re very interested in his hat,’ said the Dean.

  ‘A pointy hat always commands respect in any culture,’ said Ridcully.

  ‘Then why have several of them tried to eat it?’ said the Lecturer in Indefinite Studies.

  ‘At least they don’t appear to be warlike,’ said Ponder. ‘Let’s go and introduce ourselves, shall we?’

  And, again, when the wizards arrived at the little group around the fire there was the strange sensation of … nothing. No surprise, no shock. The heavy people treated them as if they’d just returned from the bar; their curiosity level extended perhaps to the flavour of crisps they’d brought back, but no further.

  ‘Friendly souls, ain’t they?’ said Ridcully. ‘Which one’s the boss?’

  Rincewind looked up, and then turned and snatched his hat from a big fist.

  ‘None of them,’ he snapped. ‘Stop pinching the sequins!’

  ‘Have you mastered their language?’

  ‘I can’t! They don’t have one! It’s all point and kick! That’s my hat, thank you so very very!’

  ‘We watched you walking around,’ said Ponder. ‘Surely you’ve learned something?’

  ‘Oh, yes,’ said Rincewind. ‘Follow me, and I’ll show you – give me my hat!’

  Holding his sequin-stripped hat firmly on his head with both hands, he led the wizards to a big lagoon on the other side of the village. An arm of the river flowed through it; the water was crystal clear.

  ‘See the shells?’ said Rincewind, pointing to a large heap a little way from the beach.

  ‘Freshwater mussels,’ said Ridcully. ‘Very nutritious. Well?’

  ‘It’s a big heap, right?’

  ‘And?’ said Ridcully. ‘I’m quite fond of mussels myself.’

  ‘You see that hill further along the bank? The one covered in grass? And the one behind that, with all the shrubs and trees? And the – well, see how the whole area is a lot higher than rest of the land around here? If you want to know why, just kick the soil away. It’s mussel shells all the way down! These people have been here for thousands and thousands of years!’

  The tiny clan had followed them and were watching with the uncomprehending interest that was their ground-state expression. Several of them waded in after mussels.

  ‘That’s a lot of shellfish,’ said the Dean. ‘Obviously not a taboo animal.’

  ‘Yes, and that’s surprising because frankly these people seem related to them,’ said Rincewind wearily. ‘Their stone tools are frankly rubbish and they can’t build huts and they can’t even make fire.’

  ‘But we saw a—’

  ‘Yes. They’ve got fire. They wait for lightning to strike a tree or set fire to grass,’ said Rincewind. ‘Then they just keep it going for years and years. Believe me, it took a lot of grunting and pointing to work that one out. And they have no idea about art. I mean, you know, pictures? I drew a picture of a cow in the dirt and they seemed puzzled. I really think they were just seeing … well, lines. Just lines.’

  ‘Perhaps you’re not very good at cow pictures?’ said Ridcully.

  ‘Look around,’ said Rincewind. ‘No beads, no face paint, no decoration. You don’t have to be very advanced to knock out a bear claw necklace. Even people who live in caves know how to draw. Ever seen those caves up in Ubergigle? Buffaloes and mammoths as far as the eye can see.’

  ‘I must say you’ve seemed to strike up a rapport with them very quickly, Rincewind,’ said Ponder.

  ‘Well, I’ve always been good at understanding other people enough to get an inkling of when to start running,’ said Rincewind.

  ‘You don’t always have to run, do you?’

  ‘Yes. Of course. The important thing is to know when it’s the appropriate moment, though. Ah, this one’s Ug,’ said Rincewind, as a white-haired man prodded him with a thick finger. ‘So are all the others.’

  The current Ug pointed towards the Shell Midden foothills.

  ‘He appears to want us to go with him,’ said Ponder.

  ‘He might,’ said Rincewind. ‘Or he might be pointing out where he last had a really satisfying bowel movement. See them all watching us?’

  ‘Yes.’

  ‘See that strange expression they have?’

  ‘Yes.’

  ‘You wonder what they’re thinking?’

  ‘Yes.’

  ‘Nothing. Believe me. That expression means that they’re waiting for the next thought to turn up.’

  Beyond the Shell Midden Mountains was a thicket of willows, and in the centre of the thicket was a much older tree, or what remained of one. It had been split in two, was now dead, and at some point had been burned.

  The clan hung back, but the white-haired Ug followed them into it a little way.

  Something crackled under Rincewind’s foot. He looked down, saw a yellowing bone, and nearly experienced an appropriate moment. Then he spotted the faint hummocks around the clearing, many of them overgrown.

  ‘And here’s the tree that fire came from,’ said Ridcully, who had noticed them as well. ‘Sacred ground, gentlemen. And they bury their dead.’

  ‘Not exactly buried,’ said Rincewind. ‘More just left, I think you’ll find. I think they just want to show me where they got fire.’

  Ridcully reached for his pipe.

  ‘These people really don’t make it?’ he said.

  ‘They didn’t understand the question,’ said Rincewind. ‘Well, I say question … they didn’t understand what I hope
was the question. We’re not talking progressive thinkers here. It must have been a big step when they invented the idea of taking the skins off animals before wearing them. I’ve never met any people quite so … well, dull. I can’t work them out. They’re not exactly stupid, but their idea of repartee is an answer within ten minutes.’

  ‘Well, this’ll buck their ideas up,’ said Ridcully, and lit his pipe. ‘I expect they’ll be impressed!’

  The Ugs looked at one another. They watched the Archchancellor blowing smoke. And then they attacked.

  On the Discworld the only tribe known to have absolutely no imaginations whatsoever are the N’tuiftif, although they are gifted with great powers of observation and deduction. They just never invent anything. They were the first tribe ever to borrow fire. Being surrounded by other tribes who were as imaginative as anything, they are also very good at hiding; when you are surrounded by tribes to whom a stick means ‘club, prod, lever, world domination’ you are at a natural disadvantages when, to you, a stick means ‘stick’.

  To someone else a stick currently meant ‘pole’.

  A figure vaulted across the clearing and landed in front of the Ugs.

  Orangutans do not enter the boxing ring, being too intelligent. If they did, however, the fact that they could knock out the opponent without getting up off their stool would quite make up for lack of finesse in the footwork.

  Most of the tribe turned to run, and would have come face to face with the Luggage if it had a face. They rocked when it butted them, and tried to wonder what it was. And by then the Librarian was on top of them.

  Those that worked out this was a good time to flee, fled. Those that didn’t, stayed on the ground where they had been put.

  The astonished Archchancellor was still holding the burning match when the Librarian advanced on him, screaming loudly.

  ‘What say?’ he said.

  ‘There’s a lot about him being in a library and the next minute being in the river over there,’ Ponder supplied.

  ‘That all? Sounded more.’

  ‘The rest was swearing, sir.’

  ‘Apes swear?’

  ‘Yes, sir. All the time.’

  There was another burst from the Librarian, accompanied by a pounding of knuckles on the ground.

  ‘More swearing?’ said Ridcully.

  ‘Oh yes, sir. He’s really quite upset. Hex has told him there are no longer any libraries whatsoever at any point in the planet’s history.’

  ‘Ow!’

  ‘Quite, sir.’

  ‘I burned my fingers!’ Ridcully sucked his thumb. ‘Where is Hex, anyway?’

  ‘I was just wondering that, sir. After all, the crystal ball belonged in the city which isn’t here any more …’

  They turned and looked at the tree.

  It must have blazed furiously when the lightning struck. Probably it had been dead and dry anyway. There were only a few stumps of branches. The whole thing was black, and strangely ominous against the green of the willows.

  Rincewind was sitting at the top.

  ‘What the hell are you doing up there, man?’ Ridcully bellowed.

  ‘I can’t run across water, sir,’ Rincewind called down. ‘And … I think I’ve found Hex. This tree talks …’

  TWELVE

  EDGE PEOPLE

  RINCEWIND’S ‘EDGE PEOPLE’ are a caricature of early hominids, and quite close to what anthropologists used to think Neanderthals were like.

  We now think that Neanderthals had a bit more going for them, quite apart from burying their dead. At least, it suits the mood of the times to desire to think that they did have something happening behind that big brow-ridge. A bone with holes in it, which some archaeologists believe to be a 43,000-year-old Neanderthal bone flute, has been found in Slovenia. But others dispute that it is a musical instrument. Francesco d’Errico and Philip Chase have studied the bone carefully, and they are certain that the holes were gnawed in it by animals, not bored by a musically minded Neanderthal. We do not know if it’s been handed to a musician …

  Whatever the status of the flute, it is clear that Neanderthal culture didn’t change significantly over long periods of time. The culture that led to us did. It changed dramatically, and so far it’s never stopped.

  What made us so different from the Neanderthals?

  According to the Out of Africa theory, our ancestors, and everybody else’s, came from an original population that evolved in Africa. They migrated through the Middle East; the ones bound for Australia probably left from South Africa, but might have gone round through the Far East and Malaysia. If you’ve got boats, you can do either.

  In principle the immune-gene story that we discussed in Chapter 10 could tell us more, but nobody’s yet done the research: either the Australian ‘aborigines’ have the same gene spectrum as the rest of us post-bottleneck humans, or they have their own small and characteristic selection instead. Whichever is the case, it will tell us something interesting, but until someone gathers the genetic data, we have no idea which interesting thing it will tell us. A lot of science is like that, a win-win situation. But try explaining that to the bean-counters who control research funding.

  When we speak of ‘migrations’ in this context, you shouldn’t think of the exodus of the Hebrews from Egypt. It wasn’t a case of one group of humans taking forty years or whatever and conquering other hominids along the way. It was more likely the successive formation of small settlements, slowly getting further and further away from the original homeland. The people themselves didn’t even know that they were migrating. It was just ‘Hey, Alan, why don’t you and Marilyn settle down to hunter-gathering a couple of valleys over, by that nice Euphrates river?’ Then, after a hundred years, there would be a few settlements on the far side of the river, too. This isn’t pure speculation: archaeologists have found some of the settlements.

  If humans formed new settlements a mile away every ten years, it would take only 50,000 years, a mere 1,000 grandfathers, for them to diffuse from Africa all the way to the frozen north. And they surely diffused faster than that. Hardly anybody actually went anywhere; it was just that the kids set up home a few hundred yards along the track, where there was a bit more room to bring up their kids.

  As we diffused, we diversified. It is impressive how diverse we are, physically and culturally. But perhaps, from the elvish viewpoint, we’re all much the same, from Chinese to Inuit to Maya to Welshman. Our similarities are far greater than our differences.1 We had diversified in Africa, too, from the tall willowy Masai and Zulus to the !Kung2 ‘pygmies’ and the stout Yoruba. These peoples are really, anciently, different: they differ from us, and from each other, almost as much as wolves differ from jackals. The post-bottleneck humans differentiated quite recently, just as the breeds of dogs differentiated from one kind of wolf (or perhaps it was a jackal).

  This kind of rapid differentiation is a standard evolutionary story, called ‘adaptive radiation’. ‘Radiation’ means ‘spread’, and ‘adaptive’ means that the organisms change as they spread, adapting to new environments – and, especially, to the changes brought about by their own adaptive radiation. It happened to ‘Darwin’s finches’, where one small group of finches of a single species arrived in the Galápagos islands, and within a few million years had radiated into 13 separate species, plus a 14th on the Cocos Islands. (We wonder what the legend of The Fourteenth Finch might be.) Another well-known example is the vast array of cichlid fish that diversified in Lake Victoria over the last half a million years or so. There they produced variants for the catfish niche, for the planktonic filter-feeder, for the general-detritus feeder; they evolved into species with big crushing teeth for eating mollusc-shells, species that specialised in scraping scales or fins off other fish, and species that specialised in eating the eyes of other fish. Yes, really: when fish from that species were caught, all they had in their stomachs was eyes.3 These cichlids ranged in size from a couple of centimetres to half a metre. The original
river-dwelling species Haplochromis burtoni, whose descendants they all are, grows to a length of 10–12 centimetres.

  Curiously, the range of genetics of these fishes was quite small, considering their morphological and behavioural ranges: about the same as out-of-Africa humans, but not as wide as in-Africa humans. At least, that’s the case according to some reasonable ways to estimate genetic diversity.

  The second part of this story nearly always involves extinction: just occasionally, one of the newly differentiated species has evolved a new and successful trick, and survives while all the others perish. But the usual demise of these specialised, adaptively radiated fish happens when a professional specialist – a catfish perhaps, whose ancestors have been feeding on detritus for 20 million years – comes in and takes over from the amateur cichlid catfish. Unfortunately, in this case, it wasn’t an inoffensive catfish, but the Nile perch, a specialised carnivore from an ancient stock. The Nile perch has now cleaned out nearly all of the Lake Victoria cichlid explosion, which is why we wrote the previous passage in the past tense.4 The main remnants of that glorious radiation of the cichlids are now to be found in the homes of a few amateur hobbyists, who are keeping some of the odd cichlid species in aquaria, and the Geoffrye Museum in London, which by chance has one of the largest ranges of cichlids and is now sponsored by public bodies. We don’t know yet if any of the cichlid variants in Lake Victoria has hit on a trick to survive even the Nile Perch.

  It’s difficult to know what Nile Perch is about to come in and prune Homo sapiens’ current diversity. With luck, it will be our own propensity to miscegenation, aided and abetted by airlines, despite the contrary admonitions of our priests. Maybe we’ll all be mixed up into one fairly diverse type. Or maybe it will be Independence Day aliens, out to conquer the galaxy. Or perhaps more competent ones, with elementary virus protection software.