First, genuine mutations are very rare in nature. Secondly, most mutations are harmful since they are random, rather than orderly changes in the structure of genes; any random change in a highy ordered system will be for the worse, not for the better. For example, if an earthquake were to shake a highly ordered structure such as a building, there would be a random change in the framework of the building, which, in all probability, would not be an improvement.
B. G. Ranganathan, Origins?, Pennsylvania: The Banner Of Truth Trust, 1988. (emphasis added)