Charles Darwin wrote in The Origin of Species that "... unless profitable variations do occur, natural selection can do nothing." As Darwin recognised, natural selection reduces variation in favour of an optimum type. So, what is the true source of variation in evolutionary systems? This is a question which has obsessed Warwick Collins, a novelist who had studied biology at University and for much of his adult life.In March 2000, Collins claimed that the required degree of variation could be achieved if large numbers of inert or silent genes existed within the genome. Such genes, because they do not code for physical characteristics, could freely mutate over time without deleteriously affecting the host organism. At a later stage they could be switched on, by largely random processes, and generate exotic new variants. Remarkably, his description of silent genes was found to correspond precisely with the so-called junk genes. Just as Collins predicted, the vast majority of significant mutation in the genomes of complex species arises from the silent genes. But Collins' powerful and ambitious theory moves well beyond the molecular realm. He argues that while natural selection is a major force in evolution, the great driver of complex evolution is the range of variation created by the silent genes. As Professor Donald Braben writes in his illuminating foreword, "Collins is proposing a general evolutionary theory which, if it continues to be supported by the data, may in due course come to rival Darwin's theory that evolution is driven by natural selection."