And at this point, painting came to the surface again, became... I'd... I'd needed a break, I'd been overworking and it was a wonderful, wonderful time in Malta where I was able to look back at my past. And I looked back at London and I thought that was an extraordinary time in London, it was... what was... what is a human animal like me doing in a city of that size? I'm a tribal animal.

And I sat there and I thought, hang on, I must write about this. Because outside the city, outside the urban world, I could look at it dispassionately and say, what are people doing in those great cities? And I'd come up with this expression that somebody had used saying the city is a concrete jungle. I thought, jungles aren't like that, the city's not a concrete jungle – it's a human zoo. We put animals in cages in zoos and they manage to survive in... and somehow or other, human beings survive in cities of millions of people. But they are tribal individuals. We spent a million years as hunter-gatherers. It forged the human character. And it set up a relationship between males and females which was crucially important where the males became specialised as hunters and the females did virtually everything else. And the females are actually the centre of tribal society. They were in the settlement; they were doing everything except hunting.

And the reason... this wasn't... somebody said, oh, you're just fostering the idea of the mighty hunter and the little woman at home. No, no, no – it wasn't like that. The reason that men went hunting – because they were expendable, you could... you could afford to lose a few men. Women were too important in a small tribe – the tribes were only 80, 100 people – you couldn't afford to lose women on the hunt. Because the hunt was dangerous, men were expendable; if you lost a few hunters on the hunt, it didn't matter because you've still got your females and you could breed. Breeding was tremendously important in these tiny, tiny groups. And it also became very important that because the males had to go off hunting and leave the females behind – this is something no other primate, no other monkey or ape had ever done – and so there had to be some sort of bond otherwise the men would go off hunting and they wouldn't come back or, when they came back, the females wouldn't be there. So what happened was that we slowly evolved a bond of attachment between males and females and we became a pair-bonding species which was different from the behaviour of other apes.

And we also became a nest-building primate because we had to have a settlement. We had to have a place for the hunters to come back to with the kill. And we also became a feasting primate where we had celebrations when we had a feast and special occasions occurred in our life. If you're a monkey, you just eat nuts all day or fruits and so on – you don't have special moments. We had feast moments, special moments, big moments which became celebrations and it was at these moments that we started to dance and sing and paint our bodies and it was the beginning of human art was through this celebratory moment of the feast.

And I thought, well, this is this tribal species that's now living in a conglomeration of a million people or 10 million people or whatever it is. How on earth are we managing to do that? So I wrote a sequel to The Naked Ape called The Human Zoo in which I looked at the behaviour of tribes that have become super-tribes and how the status of individuals has become super-status of great leaders and how the super-status of a great leader, again, is something that's not suitable for a human male – to have that much power – and they don't always handle it very well, as we all know. And also, in cities, there's a great deal of crime and suicide and all kinds of other problems which develop because we're not evolutionarily developed enough. The cities have only been around for a few thousand years and it takes much longer than that to get some sort of genetic change in a species. So we're still a tribal animal, living in these huge super-tribes.

And I realised that somehow we manage, even in a city, to remain tribal. And the answer is to look in someone's phone book. Because if you... or address book, because there you'll find the phone numbers or addresses of members of that person's tribe. It may be 100 or 200 of them, and that's their tribe. And that tribe is interlocked with a million other tribes and there are overlaps and interlocks, but each person really only responds to a small number of people. Otherwise, when we walk down the street, we'd have to say, 'Hello!' to every person we met. Can you imagine getting down a street, a crowded street? You would... you'd never make it; it would take all day to get down a crowded street. Because, in a tribe, everybody knew everybody else.

There was no such thing in human prehistory as a stranger. Well, there may have been occasional arrival of a stranger from another tribe but within your society you knew everyone. In a city, there were a million strangers. And the way that we handled with... handled that was to treat them as non-persons. So we walked down a street and all these strangers, we just walked past them as though they were trees. We didn't respond to them. We couldn't because it... So the way we adapted to city life was to turn the city into this massive interlocked tribe – little tribes – and we didn't make any attempt to get to know everybody in that city.