Theory of descent with modification
The theory of descent with modification is one of the two main components of the Darwinian theory of evolution. The basics of the theory are that not all of the offspring of a population will express the phenotype of the population. We now know that this is due to two forces, one is genetic recombination in which the offspring poses a compliment of genes that is unique do to receiving a set of random genes from one parent or the other (although this effect is only seen in sexually reproductive species)and the other is modification by random genetic mutation. Since the genetic code reads what ever base pairs are present and any base pair can be changed to any other base pair randomly any result is possibly although with decreasing probability as complexity increases. Just like a string of randomly generated letters  will produce words if it is of sufficient length any string of DNA of sufficient length will contain genes. With out any sort of selection all possible outcomes would be displayed eventually. No genetic changes constitute new information in the sense of information theory because information theory is about the transmission of information between two system, and an organism does not constitute two systems in the genetic sense.