The Science of Discworld II

bootstraps.
    The contradiction between Shakespeare’s noble sentiments and the heads-on-spikes culture in which he lived is a consequence of his position as a very intelligent intelligence in a not-very-extelligent extelligence. Many individuals possessed the nobility to qualify for Shakespeare’s praise, but their as yet rudimentary extelligence had not yet transmitted that nobility into the general culture. The culture was, or claimed to be, noble in principle – kings taking their authority from God Himself – but it was a barbarian style of nobility. And it was welded to a barbarian cruelty, the kings’ means of self-preservation.
    There may be many ways to make intelligent creatures, and many more ways to knit them together into an extelligent culture. The crab civilisation in The Science of Discworld was doing fine until its Great Leap Sideways was clobbered by an inbound comet. We made that one up, but who knows what might have happened a hundred million years ago? All we know for sure – or for a given value of ‘sure’, since even now a lot of our knowledge is guesswork – is that some things like apes turned into us. It takes a special kind of arrogance and blindness to extrapolate that story to the rest of the universe without wondering about alternatives.
    An important ingredient in our story was brains. Weight for weight, humans have far bigger brains than any other animal on the planet. The average human brain has a volume of about 1,350 cubic centimetres, which is roughly three times as great as the brain of apes with the same size body as ours. Whale brains are bigger than ours, but whales are even bigger, so the amount of whale per brain cell is greater than the amount of human per brain cell. When it comes to brains, quantity is less important than quality, of course. But a brain capable of really complicated things like carbon nanotube engineering and fixing dishwashers has to be fairly large, because the abilities of small brains are limited by lack of room to do anything interesting.
    We’ll see shortly that brains alone are not enough. Nonetheless, without brains, or adequate substitutes, you don’t get very far.
    There are two main theories of human origins. One is rather dull and probably correct; the other is exciting and most likely wrong. Nevertheless, the second one has quite a lot going for it and is a better story, so let’s take a look at them both.
    The dull, conventional theory is that we evolved on the savannahs. Roving groups of early apes trailed through the long grass, picking up whatever food – seeds, lizards, insects – they could find, much like today’s baboons. 4 And as they did so, lions and leopards prowled through the long grass looking for monkeys. Those monkeys or apes that were better at spotting the telltale flicker of a big cat’s tail, andfinding a tree rather quickly, survived to have babies; those that performed poorly at such tasks did not. The babies inherited those survival skills, and passed them on to their babies.
    What these tasks need is computational power. Spotting a tail and finding a tree are pattern-recognition problems. Your brain needs to pick out the tail-shape from a background of similarly buff-coloured rocks and mud; it has to choose a tree that is tall enough, and climbable enough, without being too climbable, and it has to be able to do it fast. A capacious brain with a big memory (of past occasions when something hairy poked out from behind a rock, and of locations for climbable trees) can pick up the visual traces of a lion much more effectively than a small brain can. A brain whose nerve cells transmit signals to each other more quickly can analyse incoming sensory data and conclude ‘lion’ a lot faster than a slower brain can. So there was evolutionary pressure on the early apes and monkeys to develop bigger and faster brains. There was also evolutionary pressure on the lions to conceal themselves more effectively, so that those bigger and faster ape and monkey brains still didn’t notice anything suspicious. So a predator-prey ‘arms race’ developed, a positive feedback loop that made both lions and apes far more effective in their ecological roles.
    That is the conventional story of human evolution. But there is another story, less orthodox, with two main sources.
    Human beings are very weird apes, indeed very weird animals altogether. They have