The first major transition, after the origin of life itself, the first major transition is the origin of the genetic code, whereby nucleic acids actually codes for proteins. The next revolution... is the origin of cells, in a sense, instead of having naked, replicating molecules, in a... either on a surface or in a liquid, you have molecules which are enclosed within compartments. And for reasons I'm sure you'll appreciate, that once you enclose a set of molecules in a compartment or a cell of some kind, then, to some extent, co-operation between those molecules is enforced, they've got to co-operate because they live and die together, so to speak, and they sink or swim together. And we attempted to do the formal mathematics of this. I mean, I think our philosophy is that you have to think in words but you have to prove it in more formal mathematical terms. And each stage we tried to get some kind of verbal understanding of how the transition worked, and then tried, if it hadn't already been done, to... to develop the mathematics which would be an underpinning for what we were saying verbally. There's the origin of chromosomes, which may actually have happened after the origin of cells, i.e. tying the genes end-to-end, which has the consequence that when you replicate one of them, you replicate all of them - which again, enforces co-operation upon the entities. Then there's the origin of so-called eukaryotic cells, cells with a nucleus and all sorts of organelles inside them. There's the origin of multicellular organisation in which an organism consists not of one cell but of many cells. There's the origin of society, as in the social insects, and in humans. And finally, the last transition, or the last one we discussed, it's not the last one that's going to happen, the last transition is the origin of language, in which most of the information passed between generations, as in humans, or if not most, a great deal of it, is transmitted not by genetic signals but by linguistic signals. So we've got a kind of dual inheritance system; we transmit information in parallel, by words and by genes. We don't cope with the transition we're now living through, which is the electronic revolution, in which information, in fact, is transmitted electronically, between people and between generations.

You've characterised this as differences in the way information flows through generations, I suppose there's also another theme, which is that selfish entities at one level come together and form a new entity at the next level up. Apart from the... from language itself, almost all your other transitions do have that property.

That's right, yes, it does seem that you have entities like... I mean, it's most obvious, perhaps, in the many-celled organised case, where before the transition, you have cells which reproduce on their own, afterwards. I mean, a kidney cell or a liver cell can't reproduce indefinitely on its own, it may divide for a time within the body; but, you know, its future depends upon the replication of the egg and sperm cells. And this does present a problem. I mean, you have to explain how is it that the integration, the co-operation at the higher level, wasn't disrupted by selection at the lower level. And I... I wouldn't say we've solved all these problems. I mean, I think we've formulated most of them pretty sharply, and some of them, I think, are solved, and some of them, I would have thought, are very much up for grabs.