We call them 'woods-apes', dryopithecines. Some, known as Ramapithecus, were of lighter build
-the jargon is 'gracile'. Others, such as Sivapithecus, were big and strong -'robust'. The lineage of Sivapithecus was the one that led to orangutans. These early apes would have been shy, morose creatures like today's wild apes, occasionally playful, but the adults would have been very belligerent and conscious of status within the group.
The forests inhabited by the woods-apes slowly dwindled as the climate cooled and dried, and grasslands -savannah country -took over. There were ice ages, but in the region of the tropics these did not reduce temperatures severely. However, they did change the patterns of rainfall.
The monkeys thrived, producing many ground-living kinds like baboons and vervets, and the ape populations got smaller.
By ten million years ago, there were few apes left. There are almost no fossil apes from that period. It seems plausible that, as now and as previously, those apes that did still exist were forest creatures. Some, like today's chimpanzees, gorillas and orangutans, were probably common in a few locations in the forests, but you'd have needed a lot of luck to find them. The observing elf might, even then, have put all of these apes on its Endangered List of Earth Mammals. Like very nearly all animal groups that had evolved, the forest apes were soon to be history rather than ecology. The common ancestor of humans and chimpanzees was, then, a not very remarkable ape that probably lived much as the different chimpanzees do now: some in flooded forest like today's bonobos, some in rain-forest, and some in fairly open woodland grading into grasslands. The gorilla lineage separated from the other apes around this time.
At first, the elf would probably not have been very interested as -according to one of the two popular theories of human origins - a new kind of ape began to evolve a more upright stance than those of its relatives, lost its hair, and moved out on to the savannah. Many other mammals did the same; there was a new kind of living to be made on the great grass plains. Giant hyenas, massive wild dogs, lions and cheetahs made a good living from the vast herds of herbivores that lived on the productive savannah grasses; the giant pythons were probably originally savannah animals, too.
The story has been told many times, in many versions. And that's just the point: we understand our ancestry through story. We wouldn't be able to work out our ancestry from the fossils that we have discovered unless we'd learned just what clues to look for, especially since few fossil sites have enough evidence left.
The new ancestral plains ape saw the world differently. Judging from the behaviour of today's chimpanzees, especially bonobos, it was a highly intelligent animal. We call their fossils southern apes, australopithecines, and there are hundreds of books that tell stories about them.
They may have sojourned by the sea, doing clever things on beaches. Some certainly lived on lake margins. Today's chimpanzees use stones to smash hard nuts open, and sticks to extract ants from nests; the australopithecines also used stones and sticks as tools, rather more so than their cousins the chimpanzees now do. They may have killed small game, as chimpanzees do. They probably used sexual behaviour to hang much of their pleasure on, like today's bonobos, but most likely they were more gender-conscious and male-dominant. Like previous apes, they diverged into gracile and robust lines. The robust ones, called Anthropithecus boisi, or even a different genus Zinjanthropus ('nutcracker man') and other defamatory names, were vegetarians like today's gorillas, and probably left no descendants in modern times.
This kind of split into gracile and robust forms, by the way, seems to be one of the standard patterns of evolution. Mathematical models suggest that it probably happens when a mixed population of big and small creatures can exploit the environment more effectively than a single population of medium-sized ones, but this idea has to be considered highly speculative until more evidence comes in. The zoological world was recently given a reminder of how common such a split is, and of how little we really know about the creatures of our own planet.
The animal involved could not have been better known, nor more appropriate to Discworld: the elephant.34 As every child learns at an early age, there are two kinds of elephant, two distinct species: the African elephant and the Indian elephant.
Not so. There are three species. Zoologists have been arguing for at least a century about what they thought was at most a subspecies of 'the' African elephant Loxodonta africana. The typical big, burly African elephant lives on the savannah. The elephants that live in the forest are shy, and difficult to spot: there is just one of them in the Paris zoo, for example. Biologists had assumed that because the forest elephants and the savannah elephants can interbreed at the edges of the forest, they could not be separate species. After all, the standard definition of a species, promoted by the evolutionary biologist Ernst Mayr, is 'able to interbreed'. So they either insisted that there was just one species, or that 'African elephant' had a distinguished subspecies, the forest elephant Loxodonta africana cyclotis. On the other hand, zoologists who have had the good fortune to see forest elephants are in no doubt that they look very different from the savannah ones: they are smaller, with straighter, longer tusks, and round ears, not pointed ones.
Nicholas Georgiadis, a biologist at the Mpala Research Centre in Kenya, has said: 'If you see a forest elephant for the first time, you think, "Wow, what is that?'" But because biologists knew, on theoretical grounds, that the animals had to be all the same species, the observational evidence was rejected as inconclusive.
However, in August 2001 a team of four biologists - Georgiadis, Alfred Roca, Jill Pecon-Slattery and Stephen O'Brien -reported in the journal Science their 'Genetic evidence for two species of elephant in Africa'. Their DNA analysis makes it absolutely clear that the African elephant really does come in two distinct forms: the usual robust form, and a separate gracile form. Moreover, the gracile African elephants really are a different species from the robust ones. As different, in fact, as either African species is from the Indian one. 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,35 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 trumpeting through 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?