Humans have taken privilege to a qualitatively new level. Human parents invest an astonishing amount of time and effort in their children, and spend decades -entire lifetimes, in many ways looking after them. In conjunction with big brains, slowly getting bigger as each generation passes, privilege leads to two new tricks, learning and teaching. Those tricks feed off each other, and both require the best brain you can acquire.31

Genes are involved in building brains, and genes can perhaps predispose individuals to be unusually good at learning or teaching. However, both of these educational processes involve far more than mere genes: they take place within a culture. The child does not just learn from its parents. It learns from its grandparents, from its siblings, from its aunts and uncles, from the whole troupe or tribe. It learns, as all parents discover, to their dismay, from undesirable sources as well as authorised ones. Teaching is the attempt to transmit ideas from the adult brain to that of the child; learning is the child's attempt to insert those ideas into its brain. The system is imperfect, with a lot of garbled messages along the way, but despite its faults it is much faster than genetic evolution. That's because brains, networks of nerve cells, can adapt much more rapidly than genes can.

The faults, oddly enough, probably accelerate the process, because they are a source of creativity and innovation. An accidental misunderstanding may sometimes lead to an improvement.32 In this respect, cultural evolution is just like genetic evolution: it is only because the DNA copying system makes mistakes that organisms can change.

Culture didn't arise in a vacuum: it had many precursors. One crucial step towards the development of culture was the invention of the nest. Before nests came into being, any experimentation by the young either worked, or led to a quick death. Within the protection of the nest, however, young animals can try things out, make mistakes and profit from them; for example, by learning not to do the same thing again. Outside the nest, they never get a chance to try a second time. In this manner nests led to another development, the role of play in educating the young animal. Mother cats bring half-dead mice for their kittens to practise hunting on.

Mother birds of prey do the same for their offspring. Polar bear cubs slide down snow-slopes and look cute. Play is good fun, and the kids enjoy it; at the same time, it equips them for their adult roles.

Social animals, ones that gather in groups and operate as groups, are a fertile breeding-ground for privilege and for education. And with appropriate communication, groups of animals can achieve things that no individual can manage. A good example is dogs, which evolve the ability to hunt in packs. When such tricks are being played, it is important to have some recognition signal that lets the pack distinguish its own members from outsiders, otherwise the pack can do the work and then an outsider can steal the food. Each dog pack h its own call-sign, a special howl that only insiders know. The more elaborate your brain, the more elaborate the communication from brain to brain can be, and the more effectively education works.

Communication helps with the organisation of group behaviour, and it opens up survival techniques that are more subtle than bashing others on the head. Within the group, cooperation becomes a far more viable option. Today's great apes generally work as small groups, and it seems likely that their ancestors did the same. When humans split off from the chimpanzee lineage, those groups became what we now call tribes.

Competition between tribes was intense, and even today some jungle tribes in South America and New Guinea think nothing of killing anyone they meet who comes from a different tribe.

This is a reversion to the 'bash on the head' option, but now one group cooperates to bash the other group's members on the head. Or, usually, one such member at a time. Less than a century ago, most such tribes did the same (one of the stories we've told ourselves throughout our tribal history is that we are The People, The True Human Beings -which means that everyone else isn't).

Chimpanzees have been observed killing other chimpanzees, and they regularly hunt smaller monkeys for meat. That isn't cannibalism. The food is a different species. Most humans cheerfully consume other mammals, even quite intelligent ones like pigs.33

Just as dog-packs need an agreed recognition signal to identify their members, so each tribe needs to establish a distinct identity. The possession of big brains makes it possible to do this by means of elaborate, shared rituals.

Ritual is by no means confined to humans: many species of birds, for instance, have special mating dances, or engage in strange devices to attract the female's attention, like the decorative collections of berries and pebbles assembled by the male bower-bird. But humans, with their highly developed brains, have turned ritual into a way of life. Every tribe, and nowadays every culture, has developed a Make-a-Human kit whose object is to bring up the next generation to adopt the tribal or cultural norms and pass them on to their own children.

It doesn't always work, especially nowadays when the world has shrunk and cultures clash across non-geographical boundaries -Iranian teenagers accessing the Internet, for example -but it still works surprisingly well. Corporations have taken up the same idea, with 'corporate bonding'

sessions. This is what the wizards were up to with their paintballs. Studies have shown that sessions of this kind have no useful effect, but businesses still waste billions on them every year.

The second most probable reason is that such sessions are fun anyway. The first most probable is that everyone likes an opportunity to shoot Mr Davis in Human Resources. And one important reason is that it sounds as though it ought to work; our culture is full of stories where such things do.

An important part of the Make-a-Human kit is the Story. We tell our children stories, and through those stories they learn what it is like to be a member of our tribe or our culture. They learn from the story of Winnie the Pooh getting stuck in Rabbit's hole that greed can lead to constraints on food. From the Three Little Pigs (a civilising story, not a tribal one) they learn that if you watch your enemy for repetitive patterns, you can outwit him. We use stories to build our brains, and then we use the brains to tell ourselves, and each other, stories.

As time passes, those tribal stories acquire their own status, and people cease to question them because they are traditional tribal stories. They acquire a veneer of -well, the elves would call it

'glamour'. They seem wonderful, despite numerous obvious faults, and most people do not question them. On Discworld, precisely this process occurred with stories and folk-memories about elves, as we can illustrate with three quotations from Lords and Ladies. In the first, the god of all small furry prey, Herne the Hunted, has just come to the terrified realisation that 'They're all coming back!' Jason Ogg, who is a blacksmith, the eldest son of the witch Nanny Ogg, and not very bright, asks her who They are:

'The Lords and Ladies,' she said.

'Who're they?'

Nanny looked around. But, after all, this was a forge ... It wasn't just a place of iron, it was a place where iron died and was reborn. If you couldn't speak the words here, you couldn't speak

'em anywhere.

Even so, she'd rather not.

'You know,' she said. 'The Fair Folk. The Gentry. The Shining Ones. The Star People. You know.'

'What?'

Nanny put her hand on the anvil, just in case, and said the word.

Jason's frown very gently cleared, at about the same speed as a sunrise.