The Science of Discworld Revised Edition

selective reporting. How many fossil hunters owned a bit of dinosaur bone but
didn’t
make the connection after seeing the movie?
    In the human mind, dinosaurs resonate with myths about dragons, common to many cultures and many times; and many miles of suggestions have appeared to explain how the dragon-thoughts in our minds have come down to us, over millions of years of evolution, from real dinosaur images and fears in the minds of our ancient ancestors. However, those ancestors must have been
very
ancient, for those of our ancestors that overlapped the dinosaurs were probably tiny shrewlike creatures that lived in holes and ate insects. After more than a hundred million years of success, the dinosaurs all died out, 65 million years ago – and the evidence is that their demise was sudden. Did proto-shrews have nightmares about dinosaurs, all that time ago? Could such nightmares have survived 65 million years of natural selection? In particular, do shrews today have nightmares about fire-breathing dragons – or is it just us? It seems likely that the dragon myth comes from other, less literal, tendencies of that dark, history-laden organ that we call the human mind.
    Dinosaurs exert a timeless fascination, especially for children. Dinosaurs are genuine monsters, they actually existed – and some of them, the ones we all know about, were gigantic. They are also safely dead.
    Many small children, even if they are resistant to the standard reading materials in school, can reel off a long list of dinosaur names. ‘Velociraptor’ was not notable among them before
Jurassic Park
, but it is now. Those of us who still have an affection for the brontosaur often need to be reminded that for silly reasons science has deemed that henceforth that sinuous swamp-dwelling giant must be renamed the apatosaur. 3 So attuned are we to the dinosaurs that the drama of their sudden disappearance has captured our imaginations more than any other bit of palaeontology. Even our
own
origins attract less media attention.
    What about the sudden demise?
    For a start, quite a few scientists have disputed that it ever
was
sudden. The fossil record implicates the end of the Cretaceous period , 65 million years ago, as ‘D-Day’. This was also the start of the so-called Tertiary period, or Age of Mammals, so the end of the dinosaurs is usually called the K/T boundary –‘K’ because Germans spell Cretaceous with a K. But if we assume that the end of the Cretaceous was ‘when it happened’, then many species seemed to have anticipated their end by vanishing from the fossil record five to ten million years earlier. Did amorous dinosaurs, perhaps, say to each other ‘It’s just not worth going through with this reproduction business, dear – we’re all going to be wiped out in ten million years.’? No. So why the fuzzy fade-out over millions of years? There are good statistical reasons why we might not be able to locate fossils right up to the end, even if the species concerned were still alive.
    To set the remark in context: how many specimens of
Tyrannosaurus rex
, the most famous dinosaur of all, do you think that the world’s universities and museums have between them? Not copies, but originals, dug from the rock by palaeontologists?
    Hundreds … surely?
    No. Until
Jurassic Park
, there were precisely
three
, and the times when those particular animals lived have a spread of five million years. 19 more fossilized
T. rexes
have been found since, probably more by the time you read this, because
Jurassic Park
gave dinosaurs a lot of favourable publicity, making it possible to drum up enough money to go out and find some more. With that rate of success, the chance of a future race finding any fossil humanoids, over the whole period of our and our ancestors’ existence, would be negligible. So if some species had survived on Earth for a five million year period, it is entirely likely that
no
fossils of it will have been found – especially if it lived on dry land, where fossils seldom form. This may suggest that the fossil record isn’t much use, but quite the contrary applies. Every fossil that we find is proof positive that the corresponding species did actually exist; moreover, we can get a pretty accurate impression of the grand flow of Life from an incomplete sample. One lizard fossil is enough to establish the presence of lizards – even if we’ve found only one species out of the ten thousand that were around.
    Bearing