The Science of Discworld Revised Edition

sir,’ said Ponder. ‘I didn’t think there would be any proper trees yet.’
    ‘Well, here they are,’ said Ridcully. ‘And I can see at least another three more …’
    Rincewind had already started to run. The fact that nothing can harm you is no reason for not being scared. An expert can
always
find a reason for being scared.
    The fact that the nearest trunk had toenails was a good one.
    From among the ferns above, a large head appeared on the end of too much neck.
    ‘Ah,’ said Ridcully calmly. ‘Still bloody lizards, I see.’

THIRTY-SIX
RUNNING FROM DINOSAURS

    WALKING WITH DINOSAURS was a very popular television series in the UK in 2000-2001, and it was equally popular on US television soon afterwards. It portrayed dozens of kinds of dinosaur, all beautifully realised as computer animations in the most intimate detail. And it told us things like ‘These doofersaurs were herbivorous, and they were brightly coloured to break up their outline, as protection against predation by thingumosaurs. They were monogamous, rearing their well-protected offspring by living in caves and permitting the children only very restricted access to computer games.’
    All this from just two fossil bones – one for each beast.
    Walking with Dinosaurs
was the latest in a series of popularisations of dinosaurs, from H.G. Wells’s
Outline of History
and Arthur Conan Doyle’s
The Lost World
to Walt Disney’s
Fantasia
and Michael Crichton’s
Jurassic Park
. Dinosaurs are redolent with mana; they ooze charisma. They are the PR person’s wildest dream. What gives dinosaurs such potency?
    The psychologist Helen Haste has taken over from palaeontologist Beverley Halstead the theme of dinosaurs as icons of power and sex in our civilised myth-making. Both have shown that by mythologising them into such potent symbols, we have made it very difficult to work out what it must really have been like when dinosaurs walked the Earth. Our mental images of dinosaurs carry a lot of excess baggage, and it’s hard to get away from the lies-to-children involved in those images.
    We’ll do our best, nonetheless. Whatever it was like, we’re sure that
Running from Dinosaurs
is a more apt image.
    We have a good idea of what it
wasn’t
like. We’ve all seen the standard filmic shot of dinosaur ‘ecology’, and it wasn’t like that. The camera homes in on some archaic-looking trees, and we discover a clearing with a lake and some enormous vegetarian reptiles. A few little birdy creatures get into the picture doing their little birdy things; there are pterodactyls flying about … Then there’s a great roar, and a tyrannosaur comes crashing in from stage left. He (nobody can believe it’s a ‘she’ as portrayed: we have to be informed of that in the
Jurassic Park
sequel) jumps on to a brontosaur or a hadrosaur or whatever, and wrestles it to the ground. Or he has a great teeth-against-horns fight with a triceratops, or some other armoured vegetarian like the stegosaur in Disney’s
Fantasia
.
    In the natural history books of the late nineteenth and early twentieth centuries, the drawings always show these creatures in mortal combat, too (labelled, for example ‘Ideal Scene of the Middle Oolitic Period’). Wells’s
Outline of History
was atypical in this regard; the drawings and Plates showed the animals simply going about their business, without the drama.
    What was it really like?
    For a start, there wasn’t an ‘it’. Dinosaurs, and other great reptiles, had nearly two hundred million years of being the most interesting, most important – well, the biggest, at least – land animals, and they re-invaded the sea and even produced the largest flying creatures that have ever been. Dinosaurs began, about two hundred and forty million years ago, with a single species. The earliest descendants of which we have fossils are the herbivore
Pisanosaurus
, about three feet (1m) long, and
Eoraptor
, a predator of similar size, which date from about 230 million years ago.
    By 215 million years ago the dinosaurs had diversified considerably. There were big sprawling amphibians, heavily-built and three or four feet long, as well as a great variety of little ones looking more like big salamanders. There were the synapsid reptiles, which were bigger and held up by sturdy legs: some had great bony sails on their backs, some of them were vegetarians as big as donkeys, some were carnivores as big as hyaenas. There were many kinds of more active