We think we understand the general principles but we don’t really… understand exactly why this one step and… well, let’s take a case: what was the evolution of language? For… just to take a thumb which is very close to us, and we don’t know when it originated, we don’t know what happened, whether it did it in stages or this, that and the other. So, when you… although it may be all you can say, wave your hands and say it was done by natural selection, that’s the principle involved but what you want you to know is when it happened and what were the steps by which it went, because usually evolution goes in a series of steps. A complex thing doesn’t evolve all in one go, usually. It usually takes one step and then it takes another step and then a further step and… and so on, as far as we can tell. But naturally we only have the rather imperfect or very imperfect historical record for that. We can’t go back in time and look at dinosaurs and so on, we only have very fragmentary information. The more genetic information we have now and the more we understand about development, the easier it will be for us to try and track back in time to see what the various steps were. And some of them go back a very long time. For half time that life has been on the Earth all that was here was bacteria, you know, that… they… they were the only things around for the better part of two billion years and then there was some step which, as it were, multicellular organisms or eukaryotes as they’re called – they’re not quite the same those two – began to evolve and again we would like to know what happened with that step. So, there are many, many steps and, of course, eventually we’d like to know how life originated and there’s work going on in the Salk Institute [for Biological Studies] and other places in the world, of course, on the origin of life but it’s very difficult because we don’t have any… any of the evidence. We’ve got very little… we have no molecular fossils and yet it was clearly in a molecular event, and so we have to try and deduce it from the principles of chemistry and having bright ideas, so there’s many of those things. Now, you could argue the origin of life is so long ago and may have been… may have been a rare event that it may take a very long time to understand that. But the origin of language, I would have thought, was… was much closer and… and there are a lot of things in between.