The problem of the origin of life is in fact very easily defined, if not solved. Basically, the origin of life is to find the pathway between a beginning and an end, both of which are fairly well known today. And the beginning is something that even thirty years ago was not known. Thirty years ago, most scientists were interested in the kind of work that Stanley Miller was doing, and others... that is, reproducing in the laboratory the sum of the reactions that could have taken place on earth to make the first amino acids, for instance, which is what Miller is famous for... 1953, the same year as the double helix. What we now know is that we don't need Miller kind of chemistry, because that kind of chemistry is taking place everywhere spontaneously. The bricks of life – amino acids, sugars, fatty acids, nitrogen as the bases – are being made everywhere in our solar system, probably in other places in the galaxy, and in other places in other galaxies in the universe. What used to be called organic chemistry because it was believed to be a prerogative of living organisms, including in the last century organic chemists – organic chemistry turns out to be the most banal, the most abundant chemistry in the whole universe. And we know this because we look at... at space with a... with instruments that can analyse spectrally the radiation... very faint radiation, and there is evidence of organic molecules out there. We can... we have sent instruments on comets to analyse comets and found organic chemicals. We... specially, we've analysed meteorites that fell on earth and they contain amino acids. They contain all kinds – adenine, fine. So the bricks of life... almost certainly, those bricks were the beginning. Life started. It would be too much of a coincidence to think of the bricks being there and life starting with something else. The final outcome of the origin of life is so-called LUCA – the Last Universal Common Ancestor – which is the form of life from which all known living organisms are descended. So we have some idea of what the LUCA was because all we have to do is to look at all forms of life on earth, and what they have in common must have been present in the LUCA. I'm simplifying a little, but that basically is the same. So we have to find how it worked out. Now, from the bricks to LUCA there was a very long pathway which we know hardly anything of, except we have a fairly good idea of an intermediate in that pathway, and that's RNA. Because RNA almost certainly came before DNA for reasons that are well known now, and RNA certainly came before proteins because proteins are made by RNA. Even today, protein molecules are made with the help of RNA catalysts, transfer RNAs, messenger RNAs, and the ribosomen RNA that serves as a peptidual transfer agent.