When continents move apart - as Africa and South America, or Europe and North America, are doing now - new material forms on the ocean floor, flowing out from the mantle beneath to form huge mid-ocean ridges. The rocks in the ridges contain a record of the changes in the Earth's magnetic field, `frozen in' as the rock cooled. They show a long series of repeated reversals of the field polarity. Sometimes the `north' magnetic pole is at the northern end of the Earth, as now, but every so often the polarity flips, so that the magnetic pole near the northern end is the `south' one. Mathematical models of the Earth's magnetic field predict that such reversals occur roughly once every five million years. Count the number of reversals in the ocean-ridge rocks, multiply by five million ... again, the numbers fit reasonably well, and careful comparisons and a lot of disputation by experts lead to revised numbers that fit even better.
The Grand Canyon is a deep gash through layers of rock one mile (1.6km) thick. You have a choice. You can understand what the record of the rocks is telling you here: it took a very long time to lay down those rocks, and quite a long time - though less - for flashflooding in the Colorado river to erode them again. Or you can follow one book that until recently was displayed in the `science' section of the Grand Canyon bookstore, until a lot of scientists complained, and assert that the Grand Canyon is evidence for Noah's flood. The first choice fits huge amounts of evidence and geological understanding. The second is an excellent test of faith, because it fits absolutely nothing. A flood that lasted only 40 days could never have produced that kind of geological formation. A miracle? In that case, the Sahara desert could equally well be hailed as evidence for Noah's flood, miraculously not forming a deep canyon. Once you admit miracles, you can't pursue a logical thread.
Anyway, that's the second ingredient - Deep Time. It takes huge amounts of time to change organisms into entirely new species, if all you can do - as Darwin believed - is make very gradual changes. But even Deep Time, when combined with heritable variation, is not enough to lead to the kind of organised, coherent changes that are needed to create new species. There has to be a reason for such changes to occur, as well as opportunity and time. Darwin, as we've seen, found his reason in Malthus's contention that the unchecked growth of organisms is exponential, whereas that of resources is linear. In the long run, exponential growth always wins.
The first assertion is pretty much correct, the second highly debatable. The qualifier `unchecked' is crucial, and real populations only grow exponentially if there are plenty of resources available. Typically, the growth starts exponentially with a small population and then levels off as the population size increases. But in most species, two parents (let's think sexual species here) produce some larger number of offspring. A breeding female starling lays about 16 eggs in her life, and with `unchecked' growth, the starling population would multiply by 8 every lifetime. It would not be long before the planet was knee-deep in starlings. So, of necessity, 14 of those 16 offspring (on average) fail to breed - usually because something eats them. Just two become parents in their turn. A female frog may lay 10,000 eggs in her life, and nearly all die in various grotesque ways to achieve each two parents; a female cod contributes forty million or thereabouts of her offspring to planktonic food chains, for each two that breed. Here the multiplier, with `unchecked' growth, would be 20 million per cod-lifetime. Unchecked growth simply doesn't bear thinking about as a realistic prospect.
We suspect that Malthus plumped for linear growth of resources for a slightly silly reason. Victorian school-textbook mathematics distinguished two main types of sequence: geometric (exponential) and arithmetic (linear). There were plenty of other possibilities, but they didn't get into the textbooks. Having already assigned geometric growth to organisms, Malthus was left with arithmetic growth for resources. His main point doesn't depend on the actual growth rate, in any case, as long as it is less than exponential. As the starling example shows, most offspring die before breeding, and that's the main point here.
Given that most young starlings cannot possibly become parents, the question arises: which ones will? Darwin felt that the ones that survived to breed would be the ones best suited for survival, which makes sense. If one starling is better at finding food, or hanging on to it, than another one, then it's clear which one is more likely to do best if food supplies become limited. The better one might be unlucky and get eaten by a hawk; but across the population, starlings that are better equipped to survive are generally the ones that do survive.
This process of `natural selection' in effect plays the role of an external breeder. It chooses certain organisms and eliminates the rest. The choice is not conscious - there is no consciousness to do the choosing, and no preconceived purpose - but the end result is very similar. The main difference is that natural selection makes sensible choices, whereas human selection can make ridiculous ones (like dogs with faces so flattened they can hardly breathe). Sensible choices lead to sensible animals and plants, ones that are beautifully adapted for survival in whatever environment they happened to be in when natural selection was moulding them.
It is just like breeding new varieties of pigeon, but without a human breeder. Natural selection exploits the same variability of organisms that pigeon-breeding does. It makes choices based on survival value (in some environment) rather than whim. It is typically much slower than human intervention, but the timescale is so vast that this slowness doesn't matter much. Heritable variation plus natural selection inevitably lead, over Deep Time, to the origination of species.
Nature does it all on her own. There is no need for a series of acts of special creation. That doesn't imply that special creation has not occurred. It just removes any logical imperative for it.
Paley was wrong.
The watches don't need a watchmaker.
They can make themselves.
THIRTEEN
INFINITY IS A BIT TRICKY
IT WAS JUST GONE HALF five in the morning, too late for Nibbles and yet not time for Early Breakfast. Jogging through the grey mist, Archchancellor Ridcully saw the lights on in the Great Hall. Steeling himself in case
Ponder had students in there, he pushed open the door.
There were a few students around. One of them was asleep under the coffee spigot.
Ponder Stibbons was still on the stepladder, waving his hands through the timelines.
`Getting anywhere, Stibbons?' said Ridcully, running on the spot.
Ponder managed to steady himself just in time.
`Er ... general progress, sir,' he said, and climbed down.
`Bit of a big job, eh?' said Ridcully.
`Rather taxing, sir, yes. We've done the instructions, though. We're nearly ready.'
`Hit 'em hard, that's the style,' said Ridcully, punching the air.
`Quite probably, sir,' said Ponder, yawning.
`I was thinking while I was running, Stibbons, as is my wont,' said Ridcully.
It's going to be about the eyeball, isn't it, Ponder thought. I'm pretty good on the eyeball now, but then he'll ask about the parasitic wasp and that's a puzzler, and then he'll ask how exactly is evolution passed on and there's a god-space right there. And then he'll ask how do you get from a blob in the ocean to people by adding nothing but sunlight and time? And he'll probably say: people know they're people, did blobs know they were blobs? What bit of a blob knows that? Where did consciousness come from, then? Did the big lizards have it? What's it for? What about imagination? And even if I can think up some kind of answers to all those, he'll say: look, Stibbons, what you've got there is a lot of clockwork answers, and if I ask you how you can get from a big bang to turtles and spoons and Darwin, all you'll be able to come up with is more clockwork. How did all this happen? Who wound it up? How can nothing explode? Theology of Species makes so much sense when
'Are you all right, Stibbons?' He was aware of the Archchancellor looking at him with uncharacteristic concern.
`Yes, sir, just a bit tired.'
&nbs
p; Only, your lips were moving.'
Ponder sighed. `What was it you were thinking about, sir?' `Lots of Darwins get through this voyage, right?' `Yes. An infinite number.'
`Well, in that case-' the Archchancellor began.
`But Hex did say it's a much smaller infinite number that the number that don't,' said Ponder. `And that's an even smaller number than the very large infinity when he never goes on the voyage. And the number of infinities where he's never even born is-'
`Infinite?' Ridcully asked.
`At least,' said Ponder. `However, there is a positive side to this.' `Do tell, Stibbons.'
`Well, sir, once Origin is published, the number of universes in which it is published will also become infinite in an infinitely small space of time. So even though the book may only be written once, it will, by human standards, immediately have been written in untold billions of adjacent universes.'
`An infinite number, I suspect?' said Ridcully.
`Yes, sir. Sorry about that. Infinity is a bit tricky.'
`You can't imagine half of it, for one thing.'
`That's true. It's not really a number at all. You can't get to it starting from one. And that's the problem, sir. Hex is right, the oddest number in the multiverse isn't infinity, it's one. Just one Charles Darwin writing The Origin of Species ... it's impossible.'
Ridcully sat down. `I'll be damn glad when he finishes the book,' he said. `We'll get all those nody things sorted and get him back and I personally will hand him the pen.'
`Er ... that doesn't happen immediately, sir,' said Ponder. `He didn't write it until he was back home.'
`Fair enough,' said Ridcully. `Probably a bit tricky, writin' on a boat.'
`He thought about it a lot first, sir,' said Ponder. `I did mention that.'
`How long?' said Ridcully.
`About twenty-five years, sir.'
`What?'
`He wanted to be sure, sir. He researched and wrote letters, lots of letters. He wanted to know everything about, well, everything - silk worms, sheep, jaguars ... He wanted to be sure he was right.' Ponder thumbed through the papers on his clipboard. `This interested me. It was from a letter he wrote in 1857, and he says "what a jump it is from a well-marked variety, produced by a natural cause, to a species produced by the separate act of the Hand of God".
`That's the author of The Origin? Sounds more like the author of The Ology.'
`It was a big thing he was going to do, sir. It worried him.'
`I've read The Ology,' said Ridcully. `Well, some of it. Makes a lot of sense.
`Yes, sir.'
`I mean, if we hadn't watched the world all happen from Day One, we'd have thought-'
`I know what you mean, sir. I think that's why The Ology was so popular.'
`Darwin - I mean our Darwin - thought that no god would make so many kinds of barnacle. It's so wasteful. A perfect being wouldn't do it, he thought. But the other Darwins, the religious ones, said that was the whole point. They said that just as mankind had to strive for perfection, so must the whole animal kingdom. Plants, too. Survival of the Worthiest, they called it. Things weren't made perfect, but had an inbuilt, er, striving to achieve perfection, as if part of the Plan was inside them. They could evolve. In fact, that was a good thing. It meant they were getting better.'
`Seems logical,' said Ridcully. `By god logic, at least.'
`And there's the whole thing about the Garden of Eden and the end of the world,' said Ponder.
`I must've missed that chapter,' said Ridcully.
`Well, sir, it's your basic myth of a golden age at the start of the world and terrible destruction at the end of it, but codified in some very interesting language. Darwin suggested that the early chroniclers had got things mixed up. Like trolls, you know? They think the past is ahead of them because they can see it? The terrible destruction was in fact the birth of the world-'
'Oh, you mean the red hot rocks, planets smacking together, that sort of thing?'
`Exactly. And the end of the world, well, as experienced, would be the assembly of perfect creatures and plants in a perfect garden, belonging to the god.'
`To get congratulated, and so on? Prizes handed out, marks awarded?'
`Could be, sir.'
`Like an everlasting picnic?'
`He didn't put it like that, but I suppose so.'
`What about the perfect wasps?' said Ridcully. `You always get them, you know. And ants.'
Ponder had been ready for this.
`There was a lot of debate about that sort of thing,' he said.
`And it concluded how?' said the Archchancellor.
,it was decided that it was the kind of subject on which there could be a lot of debate, and that earthly considerations would not apply.'
`Hah! And Darwin got all this past the priests?'
`Oh, yes. Most of them, anyway,' said Ponder.
`But he was turning their whole world upside down!'
`Um, that was happening anyway, sir. But this way, the god didn't drop out of the bottom. People were poking around and proving that the world really was very old, that seabeds had become mountain tops, that all kinds of strange animals had lived a long, long time ago. Lots of people already accepted the idea of evolution. The idea of natural selection, as Darwin called it, of life just evolving itself, was hovering in the air. It was a big threat. But Theology of Species said there was a Plan. A huge, divine Plan, unfolding across millions of years! It even included the planet itself! All that turmoil and volcanoes and drowning lands, that was a world evolving, you see? A world that would end up with topsoil, and the right kind of atmosphere, and minerals that were easily accessible, and seas full of fish-'
`A world for humans, in other words.'
`Got it in one, sir,' said Ponder. `Humans. The top of the tree. A creature that knew what it was, that gave things names, that had a concept of epiphany. That Darwin later wrote another book, called The Ascent of Man. Oddly enough, our Darwin is going to write a similar book called The Descent of Man-'
`Ah, I can see a bad choice of words right there,' said Ridcully.
`Quite,' said Ponder. `The Ology Darwin was considered daring but ... acceptable. And there was so much evidence that this was a planet made for humans. The religion changed quite a lot, but so did the technomancy. The god was still in charge.'
'All very neat,' said the Archchancellor. `So ... what about the dinosaurs?'
Sorry, sir?'
'Mr Stibbons, you know what I'm talking about. We saw them, remember? Not the big ones, the little ones who painted their bodies and herded animals? And the octopuses building cities under the sea? Not to mention the crabs! Oh, yes, the crabs. They were really doing well, the crabs. They were building rafts with sails and enslaving other crab nations. That's practically civilisation! But they all got wiped out. Was that part of a divine plan?'
Ponder hesitated.
`They did worship a crab-shaped god,' he said, as a holding statement until actual thought happened.
`Well, they would, wouldn't they?' said Ridcully. `They were crabs.' `Um. Perhaps they just weren't ... satisfactory?' said Ponder. `In some way?'
`They were pretty clever,' said Ridcully.
Ponder squirmed. `Darwin didn't know about them,' he said. `They didn't build anything that lasted. I suppose the Darwin who wrote The Ology would have taken the view that they simply failed, or were wicked in some way. One of the major religious texts does mention a divine flood that drowned everything in the world except one family and a boatload of animals.'
`Why?'
`Because they were all wicked, I believe.'
`How can animals be wicked? How can a crab be wicked, for that matter?
'I don't know, Archchancellor!' Ponder burst out. `Maybe if they eat forbidden seaweed? Dig a burrow on the wrong day? I'm not a theologian!'
They sat in despondent silence.
`It's a bit of mess, isn't it?,' said Ridcully.
`Yes, sir.'
; `We've really got to see to it that The Origin gets written.' `We have indeed, sir.'
`But you'd like to think there's someone in charge, yes?' said Ridcully, gently. `Of everything, I mean.'
`Yes! Yes, I would, sir! Not a big beard in the sky, but ... something! Some kind of frame, some sense that good and bad have real meanings! I can see why The Ology was so popular. It wrapped everything up! But how does evolution get passed on? Where does order come from? If you start with a lot of exploding firmament, how do you end up with butterflies? Were butterflies built in from the start? How? What bit of burning hydrogen carried the plans for people? Even the Darwin who wrote The Origin called on a god to start life. It's be nice to know that underneath it all is some kind of ... sense.'
`You didn't used to talk like this, Mr Stibbons.'
Ponder sagged. `Sorry, sir. It's all getting me down, I think.'
`Well, I can see why,' said Ridcully. `Surely there must be some Deitium here. Some things can't just happen. Now, the eyeball -'
Ponder gave a little yelp.
`- is easy,' said Ridcully. `Are you all right, Stibbons?'
`Er, fine, fine, sir. I'm fine. Easy, is it?
'Seeing keeps you alive,' said Ridcully. `Any kind of seeing is better than nothing. I can see, ha, what the Origin Darwin is getting at there. You don't have to have a god. But there's a kind of wasp that's parasitical on a spider ... unless I'm thinking about a kind of spider that is parasitical on a wasp ... anyway, what it does is, it waits
until-'
`Ah,' said Ponder brightly, `wasn't that the gong for Early Breakfast?'
`I didn't hear anything,' said Ridcully.
`I'm positive,' said Ponder, edging towards the door. `I'll tell you what, sir, I'll just go and check.'
Darwin's Watch Page 16