The Science of Discworld Revised Edition

question so simple that it seems to have eluded most other workers in the field. Yes, many areas where fossils of apelike human ancestors have been found are savannahs
now
. But were they savannahs
then
? When our distant great-great-… grandparents got themselves fossilised, 2.7 million years ago, could the vegetation have been different from what it is today?
    Given that the whole point is that the animals definitely were different – our ancestors, not us – it is a little surprising that this question seems not to have occurred to anyone earlier. Unfortunately, science is often like that. People specialise. Experts on prehistoric apes may not be very interested in botany.
    It turns out that Sterkfontein, one of the places where fossil apes supporting the savannah theory are found, wasn’t a savannah back then at all. Fossil pollen suggested it was a wooded area, and fossilised lianas clinched it. Other areas of South Africa and Ethiopia (where the famous ‘Lucy’ was found) show that these areas were forests when the apes lived there. The ‘killer ape of the savannahs,’ says Tobias, is nonsense.
    And there may be some new evidence in favour of watery origins for humanity, though not necessarily the full-blooded Aquatic Ape. A common feature of fossil hominid sites is that they are all near water. This makes sense, because
Homo sapiens
needs to drink a lot, and sweats and urinates a lot. If we had evolved on savannahs, we would have annoyed the hell out of all the other animals there with our incessant peeing. And it looks like we were excellent swimmers at least a million years ago. There is evidence of human migrations to islands such as Flores, separated from Bali by a deep underwater valley . Even allowing for the lower sea-levels in the past, the new arrivals must have swum or rafted or otherwise made their way across at least 20 miles of open water.
    We may not have been the Aquatic Ape, but we surely were the Damp Forest Ape. Just as bonobos, one of our two closest living relatives, are today.
    Brains are fascinating. They are the physical vehicle for minds, which are even more interesting. Minds are (or, at least, give their owners the vivid impression that they are) conscious, and they have (or, at least, give their owners the vivid impression that they have) free will. Minds operate in a world of ‘qualia’ – vivid sense impressions like
red, hot, sexy
. Qualia aren’t abstractions: they are ‘feelings’. We all know what it’s like to experience them. Science has no idea what makes them the way they are.
    Brains, though … we can make progress on brains. On one level, brains are a kind of computational device. Their most obvious physical components are nerve cells, arranged in complicated networks. Mathematicians have studied such networks, and they find that what networks do is to carry out interesting processes. Give them an input and they will produce an output. Allow their interconnections to evolve by selecting for specific associations of input and output – such as responding to an image of a banana but not to an image of a dead rat – and pretty soon you’ve got a really effective banana-detector.
    What makes the human brain unique, as far as we can tell, is that it has become recursive. As well as detecting a banana, it can think
about
detecting a banana. It can think thoughts about its own thought processes. It is a pattern-recognition device that has turned its attention to its own patterns. This ability is what lies behind human intelligence. It probably underpins consciousness, too: one of the patterns that the pattern-recognition device has learned to recognize is
itself
. It has become ‘self-aware’.
    As a result, brains operate on at least two levels. On a reductionist level they are networks of nerve cells sending each other incredibly complex but ultimately meaningless messages – like ants scurrying around inside an anthill. On another level, they are an integrated self – the anthill as a personality in its own right. Douglas Hofstadter’s
Gödel, Escher, Bach
includes a sequence where Aunt Hillary (who is an anthill – use the American pronunciation of ‘Aunt’) has a meeting with Dr Anteater. When Dr Anteater arrives, the ants go into a panic – they change their actions. To Aunt Hillary, who operates on the emergent level, this change represents the
knowledge
that Dr Anteater has arrived. She is entirely happy to watch Dr Anteater consuming a meal of