Human beings have taken this process to such an extreme that part of that feedback loop has escaped from our control and is now outside us. In a sense, it has a mind of its own. This is extelligence, and we can't do without it. A lot of what makes us human is not passed on genetically, it is passed on culturally. It is passed on by the tribe, it is passed on through rituals, by teaching, by things that link brain to brain, mind to mind. Your genetics may make it possible for you to do this, it may make you better or worse at it than others, but genes don't actually encode the information that gets passed on. This process is the 'Make-a-Human-Being-Kit'. Each culture has devised a technique for putting into the minds of the next generation what it is that will make them put it into the minds of the generation after that, a recursive system that keeps the culture going. Lies-to-children often feature prominently.
We are running into problems doing this today, because old-style tribal cultures, even national cultures, are becoming intermingled with an international culture. This leads to clashes between what used to be separate cultures, triggering their breakdown. Go into any city in the world and you see adverts for Coca-Cola. Global commerce has put things into various cultures that are different from what they would have developed of their own accord. Coca-Cola does not have a huge influence on the Make-a-Human-Being-Kit, though, so it's acceptable to most cultures. On the whole, you don't find religious fundamentalists complaining about the existence of a Coca-Cola bottling factory in their country (well, you do, but generally because it's just a way of saying 'USA out!') However, if some fast-food chain in Islamic or Jewish countries was trying to sell porkburgers, there'd be plenty of protests.
Extelligence has become so powerful and so influential that nowadays one generation's culture may be radically different from the previous generation's culture. Second-generation immigrants often have an even worse problem, a culture clash. They've grown up in the 'new' country, and they've absorbed how that country works. They speak the language far more fluently than their parents ever can, but they've still got to please their parents. When they're at home, they have to behave in the manner of their original culture. But when they're at school, they have to live in the new culture. This makes them feel distinctly uncomfortable, and that can break the cultural feedback loop. Once the loop is broken, parts of the culture cease to be transmitted to the next generation: they drop out of the Make-a-Human-Being-Kit.
In this sense, extelligence is out of our control. It escaped our control when it became reproductive: extelligence being used to copy (bits of) extelligence.
The key step was the invention of printing. Prior to written language, extelligence was passed on by word of mouth. It still lived in people's minds: it was what the wise men and women of the village, the old people, knew. And all the while extelligence resided in human memories, it couldn't grow, because one person can remember only so much. When you could write things down, extelligence expanded a bit, but there is only so much that you can write down by hand. And it can't spread very far. So mostly you get things like the Egyptian monuments, the history of some particular ruler, his greatest battles, excerpts from the Book of the Dead ...
Another important but apparently mundane function of writing in human society is taxes, accounts, keeping track of property. These sound dull compared with the list of battles, but a growing society needs something better than an old man's memory of 'who owns what' and 'who paid how much'. The list was a great invention.
With printing came the possibility of disseminating information far more widely, and in quantity. Within a few years of printing becoming established in Europe there were fifty million books in existence, which means more books than people. Printing was a very slow procedure in those days, but nonetheless there were lots of printing presses, and you could sell whatever you printed, so there were plenty of pressures that encouraged printing to flourish. And then complicity really set in, because what's on a piece of paper can come back and bite you in the ankle. The rulers started putting constitutional rights and obligations down on paper, to protect their own position: once it's down on paper that the king has certain rights and obligations, then the paper can always be referred to later, and used as an argument.
But what the kings didn't realize, to start with, is that when they put their rights and obligations down on paper, they were implicitly constraining their own actions. The citizens could read what was on the paper too. They could tell if their king was suddenly assuming rights or obligations that were not on the piece of paper. The whole effect of law on human society started to change when you could write the law down, and anyone who could read could see what the kw was. This didn't mean that the kings always obeyed the kw, of course, but it meant that when they disobeyed it, everyone knew what they were doing. That had a big effect on the structure of human society. One minor aspect of it is that we always appear to be nervous of people who write things down...
At that point, extelligence and intelligence began to interact complicitly. Once an interaction becomes complicit, there's no way for an individual to control it. You can push things out into the extelligence, but you can't predict what influence they will have. What's out there is growing in a way that may be mediated by human beings, but, for example, the people printing books were krgely printing them independently of their contents. Early on, anything in print would sell.
All words had power. But written words had a lot more. They still do.
So far we've talked as if extelligence is a single unified external thing. In some sense it is, but what is actually important is the interface between extelligence and the individual. This is a very personal feedback loop: we meet selections from extelligence through our parents, the books we read, the teachers who teach us, and so on. This is how the Make-a-Human-Being-Kit works, this is why we have cultural diversity. If we all responded to the same pool of extelligence in exactly the same way, we would all be the same. The whole system would suddenly become a kind of monoculture rather than a multiculture.
Human extelligence is currently going through a period of massive expansion. Much more is becoming possible. Your interface to extelligence used to be very predictable: your parents, teachers, relatives, friends, village, tribe. That allowed clusters of particular kinds of subculture to flourish, to some extent independently of the other subcultures, because you never got to hear about the others. Their world view was always filtered before it got to you. In Whit, lain Banks describes a strange Scottish religious sect, and children who grow up in this sect. Even though some members of the sect are interacting with the outside world, the only important influences on them are what's going on within the sect. Even by the end of the story the character who has gone into the outside world and interacted with it in all sorts of ways has one idea in mind and one only, to become the leader of the sect and to continue propagating the sect's views. This behaviour is typical of human clusters, until extelligence intervenes.