What really matters in evolution, is the... and indeed, in biology, almost, is the transmission of information, in a quite technical sense. And that what... that occasionally, in the course of evolution, there has been a change in way in which genetic information is stored, is transmitted between generations. One of the transitions we've already talked about is sex. I mean, the change from simple division to sexual reproduction is essentially a change in the way in which information is passed on, so that instead of getting your information from one parent you get it from two, and so on. But there are a number of other major changes of this kind in the way that information is stored and transmitted. And... the book I wrote jointly with my young Hungarian colleague, Eörs Szathmáry - essentially because we tend to think very similarly about problems. I'm surprised to the extent to which when we think about a problem we seem to come up with the same kind of way of seeing it, and yet he knows a lot of chemistry and molecular biology - of which I'm rather ignorant - and I know a fair bit about behaviour and social organisation and structure of higher animals. And I wouldn't like to accuse Eors of being ignorant, but he knows less about it than I do. So we were able to sort of cover everything from the origin of life to the origin of language by... I don't think either of us could have done it on our own. And we really just tried to understand how these... these major transitions took place. Of course, in a sense, they're something of an interruption of the sort of image of evolution being a series of gradual change. We really are looking at something which one might also call a revolution or a series of revolutions.

Could we go through what some of those revolutions are.

Yes, I won't go through the whole thing, but the ones that are perhaps most familiar, we now believe that there was a period in the early period of life in which the distinction between nucleic acids as the carriers of information and proteins as the... coded by the nucleic acids, doing all the work, I mean, being the enzymes and the structural proteins and so on, that no such division of labour between an information molecule and a doing molecule existed. And that, in fact, all there was, was RNA, nucleic acid, which was both the replicator and the enzyme.