The Science of Discworld II

So now we have the robust African plains elephant Loxodonta africana and the gracile African forest elephant Loxodonta cyclotis .
    What of the belief that there could be only one species because of the potential for interbreeding? This particular definition of species is taking a hammering at the moment, and deservedly so. The main reason is a growing realisation that even when animals can interbreed, they may decide not to.
    The story of the Third Elephant is not new: only the names have been changed. Before 1929 every zoologist ‘knew’ there was only one species of chimpanzee; after 1929, when the bonobos of the inaccessible swamps of Zaire were recognised as a second species, 2 it became obvious to many zoos that they had possessed two distinct chimpanzee species for years, but not realised it. Exactly the same story is now being played out with elephants.
    As we’ve mentioned, Discworld recently revived interest in its fifth elephant, a story told, you will be surprised to hear, in The Fifth Elephant . According to legend, there were originally five elephants standing on Great A’Tuin and supporting the Disc, but one slipped, fell off the turtle, and crashed into a remote region of Discworld:
    They say that the fifth elephant came screaming and trumpetingthrough the atmosphere in the young world all those years ago and landed hard enough to split continents and raise mountains.
    No one actually saw it land, which raised the interesting philosophical question: when millions of tons of angry elephant come spinning through the sky, and there is no one to hear it, does it – philosophically speaking – make a noise?
    And if there was no one to see it hit, did it actually hit?
    There is evidence, in the form of vast deposits of fat and gold (the great elephants that support the world do not have ordinary bones), deep underground in the Schmaltzberg mines. However, there is a more down-to-Disc theory: some catastrophe killed off millions of mammoths, bison and giant shrews, and then covered them over. On Roundworld, there would be a good scientific test to distinguish the two theories: are the deposits of fat shaped like a crash-landed elephant? But there’s no point even in looking, on Discworld, because narrative imperative will ensure that they are, even if they were formed by millions of mammoths, bison and giant shrews. Reality has to follow the legend.
    Roundworld has so far reached only its third elephant, although Jack hopes that some careful selective breeding might yet bring back a fourth: the pygmy elephant, which lived in Malta and was about the size of a Shetland pony. It would make a marvellous pet – except that, like many diminutive creatures, it would probably be rather bad-tempered. And the very devil to discourage from getting on the settee.
    We are a gracile ape (not that you’d notice in some parts of the world, where many of us more closely resemble a robust hippopotamus). About four million years ago one gracile lineage of apes started to get bigger brains and better tools. Against all the rules of taxonomy we call this lineage, our lineage, Homo : it really should be Pan , because we are the third chimpanzee. We use this name because it is certainly our own lineage, and we prefer to think of ourselves as being enormously different from the apes. In this we could be right: we may indeed share 98 per cent of our genes with chimpanzees, but then,we share 47 per cent with cabbages. Our big difference from the apes is cultural, not genetic. Anyway, within the Homo lineage we again find gracile and robust stocks. Homo habilis was our gracile tool-making ancestor, but Homo ergaster and others went the vegetarian, robust way. If there actually is a yeti or a bigfoot, the best bet is a robust Homo . From Homo habilis ’s success, a larger-brained Homo spread out over Africa, into Asia (as Peking Man) and Eastern Europe about 700 million years ago.
    We have labelled one variety of these fossils Homo erectus . The visiting elf would certainly have noticed this fellow. He had several kinds of tools, and he used fire. He may even have possessed language, of a kind. What we have every reason to suspect that he did, that his ancestors and cousins only occasionally achieved, was to ‘understand’ his world and change it. Chimpanzees engage in quite a lot of ‘if … then’ activities, including ‘lying’: ‘if I pretend not to have seen