In the past, the environment was a context for us, we evolved to suit it. Now we've become a context for the environment, we change it to suit us. We need to learn how to do that, but going back to some imaginary golden age in which primitive humans allegedly lived in harmony with nature isn't the answer. It may not be politically correct to say so, but most primitive humans did as much environmental damage as their puny technology would allow. When humans came to the Americas from Siberia, by way of Alaska, they slaughtered their way right down to the tip of South America in a few tens of thousands of years, wiping out dozens of species, giant tree sloths and mastodons (ancient elephants, like mammoths but different), for example. The Anasazi Indians in the southern part of today's USA cut down forests to build their cliff dwellings, creating some of the most arid areas of the United States. The Maoris killed off the moas. Modern humans may be even more destructive, but there are more of us and technology can amplify our actions. Nevertheless, by the time humans were able to articulate the term 'natural environment', there wasn't one. We had changed the face of continents, in ways big and small.
To live in harmony with nature, we must know how to sing the same song as nature. To do that, we must understand nature. Good intentions aren't enough. Science might be, if we use it wisely.
BACKSLIDERS
GLOOM HAD SETTLED OVER THE WIZARDS. Some of them had even refused a third helping at dinner. 'It's not as if they were very advanced,' said the Dean, in an attempt to cheer everyone up. 'They weren't even using metal. And their writing was frankly nothing but pictograms.'
'Why doesn't that sort of this thing happen here?' said the Senior Wrangler, merely toying with his trifle.
'Well, there have been historical examples of mass extinction,' said Ponder.
'Yes, but only as a result of argumentative wizardry. That's quite different. You don't expect rocks to drop out of the sky.'
'You don't expect them to stay up?' said Ridcully. 'In a proper universe, the turtle snaps up most of them and the elephants get the rest. Protects the world. Y'know, it seems to me that the most sensible thing any intelligent lifeform could do on that little world would be to get off it.'
'Nowhere to go,' said Ponder.
'Nonsense! There's a big moon. And there's other balls floating around this star.'
'All too hot, too cold, or completely without atmosphere,' said Ponder.
'People would just have to make their own entertainment. Anyway ... there's plenty of other suns, isn't there?'
'All far too far away. It would take ... well, lifetimes to get there.'
'Yes, but being extinct takes forever.'
Ponder sighed. 'You'd set out not even knowing if there's a world you could live on, sir,' he said.
'Yes, but you'd be leavin' one that you'd know you couldn't,' said Ridcully calmly. 'Not for any length of time, anyway.'
'There are new lifeforms turning up, sir. I went and checked before dinner.'
'Tell that to the lizards,' sighed the Senior Wrangler. 'Any of the new ones any good?' said Ridcully. 'They're ... more fluffy, sir.' 'Doin' anything interesting?'
'Eating leaves, mainly,' said Ponder. 'There are some much more realistic trees now.'
'Billions of years of history and we've got a better tree,' sighed the Senior Wrangler.
'No, no, that's got to be a step in the right direction,' said Ridcully, thoughtfully.
'Oh? How so?'
'You can make paper out of trees.'
The wizards stared into the omniscope.
'Oh, how nice,' said the Lecturer in Recent Runes. 'Ice again. It's a long time since we've had a really big freeze.'
'Well, look at the universe,' said the Dean. 'It's mainly freezing cold with small patches of boiling hot. The planet's only doing what it knows.'
'You know, we're certainly learning a lot from this project,' said Ridcully. 'But it's mainly that we should be grateful we're living on a proper world.'
A few million years passed, as they do.
The Dean was on the beach and almost in tears. The other wizards appeared nearby and wandered over to see what the fuss was about.
Rincewind was waist deep in water, apparently struggling with a medium-sized dog.
'That's right,' the Dean shouted. 'Turn it round! Use a stick if you have to!'
'What the thunder is going on here?' said Ricully.
'Look at them!' said the Dean, beside himself with rage. 'Backsliders! Caught them trying to return to the ocean!'
Ridcully glanced at one of the creatures, which was lying in the shallows and chewing on a crab.
'Didn't catch them soon enough, did you,' he said. 'They've got webbed paws.'
'There's been too much of this sort of thing lately!' snapped the Dean. He waved his finger at one of the creatures, who watched it carefully in case it turned out to be a fish.
'What would your ancestors say, my friend, if they saw you rushing into the water just because times are a bit tough on land?' he said.
'Er ... '"Welcome back"?' suggested Rincewind, trying to avoid the snapping jaws.
"Long time no sea'?' said the Senior Wrangler, cheerfully.
The creature begged, uncertainly.
'Oh, go on, if you must,' said the Dean. 'Fish, fish, fish ... you'll turn into a fish one of these days!'
'Y'know, going back to the sea might not be a bad idea,' said Ridcully, as they strolled away along the beach. 'Beaches are edges. You always get interestin' stuff on the edge. Look at those lizards we saw on the islands. Their world was all edges.'
'Yes, but giving up the land to just go swimming around in the water? I don't call that evolution.'
'But if you go on land where you have to grow a decent brain and some cunning and a bit of muscle in order to get anything done, and then you go back to see the sea where the fish have never had to think about anything very much, you could really, er, kick butt.'
'Do fish have...?'
'All right, all right. I meant, in a manner of speaking. It was just a thought, anyway.' Uncharacteristically, the Archchancellor frowned.
'Back to the sea,' he said. 'Well, you can't blame them.'
MAMMALS ON THE MAKE
AFTER THE DINOSAURS CAME THE MAMMALS -Not exactly.
Mammals constitute the most obvious class of animal alive on Earth today. When we say 'animal' in ordinary conversation, we're mostly referring to mammals, cats, dogs, elephants, cows, mice, rabbits, whatever. There are about 4,000 species of mammals, and they are astonishingly diverse in shape, size, and behaviour. The largest mammal, the blue whale, lives in the ocean and looks like a fish but isn't; it can weigh 150 tons (136,000 kg). The smallest mammals, various species of shrew, live in holes in the ground and weigh about an ounce (30 g). Roughly in the middle come humans which, paradoxically, have specialized in being generalists. We are the most intelligent of the mammals, sometimes.
The main distinguishing feature of mammals is that when they are young their mother feeds them on milk, produced by special glands. Other features that (nearly) all mammals have in common include their ears, specifically the three tiny bones in the middle ear known as the anvil, stirrup, and hammer, which send sound to the eardrum; hair (except on adult whales); and the diaphragm, which separates the heart and lungs from the rest of the internal organs. Virtually all mammals bear live young: the exceptions are the duckbilled platypus and the echidna, which lay eggs. Another curious feature is that mammalian red blood cells lack a nucleus, whereas the red cells of all other vertebrates possess a nucleus. All is this is evidence for a lengthy common evolutionary history, subject to a few unusual events of which the most significant was the early separation of Australia from the rest of Gondwanaland. Modern studies of mammalian DNA confirm that basically we are all one big happy family.