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 Godel, Esther, 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 'her' ants. Ants are a virtually inexhaustible resource, she can always breed new ones to take the place of the ones that got eaten.

The link between the ants and Hillary's 'anthilligence' is emer­gent, felicitously, it. operates across what we have termed 'Ant Country'. The same action means one thing for the ants, but some­thing quite different, and transcendent, for Hillary. Replace Hillary by yourself, your self, the 'you' that you feel is experiencing your thoughts, and ants by brain cells, and you're contemplating the connection between mind and brain.

Now you've gone self-referential.

Neural networks are what the brain is built from, but there's more to evolving a brain than just assembling big neural nets. Brains operate in terms of high-level 'modules', a module for running, another for recognizing danger, another for putting the whole ani­mal on the alert, and so on. Each such module is an emergent feature of a complex neural network, and it wasn't designed: it evolved. Millions of years of evolution trained those modules to respond instantly and exquisitely.

The modules aren't separate. They share nerve cells, they over­lap, they're not necessarily a well-defined region in the brain, any more than 'Vodafone' is a well-defined region of the telephone net­work. According to Daniel Dennett, they are like a collection of demons, operating by 'pandemonium'. They all shout, and at any given instant, whoever shouts loudest wins (quite a lot of the Internet has borrowed this design).

Modern humanity has built a culture around those modules, an idea that we'll explore later, and in so doing has subverted them to new purposes. The module for spotting lions has become, in part, a module for reading Discworld books. The module for sensing bodily movement has, in part, turned into one for doing certain kinds of mathematics, those parts of mechanics where a physical 'feel' for the problem may well be precisely that. Our culture has rebuilt our minds, and our minds have in turn rebuilt our culture, over and over again, in each generation.

Such a radical restructuring must have simpler precursors. A key step towards the human mind was the invention of the nest. Before there were nests, baby organisms could carry out only very limited experiments in behaviour. If every time you try out a new game you get gobbled up by a python, novelty will not carry a pre­mium. In the comfort and relative safety of the nest, however, the error part of trial-and-error is no longer automatically fatal. Nests let you play, and play lets you explore the phase space of possible behaviours and find new, sometimes useful, strategies. Further along the same path lies the family, the pack, and the tribe, with cer­tain shared behaviours and mutual protection. Meerkats, a kind of mongoose, have an intricate tribal structure, and take turns doing the dangerous (because more exposed) job of Lookout.

Humans have turned such tactics into a global strategy: adults devote huge amounts of time, energy, food, and money to the task of bringing up their children. Intelligence is both a consequence of this brilliantly successful strategy, and a cause.

The Dean would be well advised to take this link between family life and intelligence into account. He's trying to educate the apes by the direct route (R ... O ... C ... K ...) but all they have on their tiny minds is S-E-X. Many school teachers will sympathize ... but if only he realized that sexual bonding is a major factor in humanoid family life, and family life engenders intelligence ,..

Bonobos are the perfect model for the Dean's sex-mad apes. They are promiscuous in the extreme, making use of sex where we would be content with a smile and a wave or a gentlemanly hand­shake. Female bonobos have serial sex with dozens of males, or with females, almost in passing; the males do likewise. Adults engage in sexual activities with children, too. It all seems very casual. It helps bond the tribe. For them it seems to work fine.

Ordinary chimps are promiscuous by the standards of orthodox human morality, though probably no more than many humans are. Pairs of males and females will disappear together for a few days, and then form new partnerships ... Humans generally mate for life (a term meaning 'until we get fed up') and one reason is the enor­mous amount of effort that a human couple must put into raising the kids. Sex helps to cement the parental relationship, encouraging each parent to trust the other. This .may be why, even in an allegedly sexually relaxed age, most people see extramarital flings as a form of betrayal, and why, despite that, the erring partner is more often than not allowed back into the family fold.

It's not surprising that we have sex on the brain: our brains have been moulded by sex. The Dean should let sex take its course, for intelligence will surely follow ... You just have to think on the scale of Deep Time. There's no rush.

OOK: A SPACE ODYSSEY

RINCEWIND SAT IN A CORNER of the High Energy Magic building. It was deserted at the moment. News had got around that the project was really being ended this time, and wizards had drifted away to lunch.

The round world spun in its protective globe and also, by means of a physics only a wizard might understand, in a space that was infinite only on the inside.

'Poor old bloody place,' he said, to the world in general. 'Never really stood a chance, did you.'

'Ook.'

It was a small grunt, from the other side of the huge room. Rincewind wandered over, and found the Librarian peering into the omniscope.

'Oh, they've got sticks now,' said Rincewind, looking down at a ragged party of apes. 'And a lot of good it'll do them, too.'

'Ook?'

'The lizards had sharp shells on the end of theirs, and are they around today? I don't think so. And the crabs were doing well. Even the blobs were trying to make a go of things. There were some bear sort of things that looked promising. Doesn't matter. One winter the snow doesn't melt, next thing there's a two-mile wall of ice lam­inating you to the bedrock. Or there's a funny light in the sky and then you're trying to breathe burning water.' He shook his head wearily. 'Nice place, though. Nice colours. Particularly good hori­zons, once you get used to them. Lots of dullness, punctuated by short periods of death.'

'Ook?' said the Librarian.

'Well, maybe they do look a bit like you,' said Rincewind. 'Most of the lizards looked a bit like the Bursar. Maybe it's just coincidence. Everything has to look like something, after all. As above, so below.'

In the omniscope, some distance behind the ape clan, something lean and powerful was tracking them in the long grass.

'Eeek!'

The Librarian thumped on the desk.

'Sorry. It's not up to me. "Live and let live", you know that's always been my motto. Well, "let me live", really, but that's almost the same thing.'