The Classical Iterated Prisoner's Dilemma (CIPD) is used to study the evolution of cooperation. We show, with a genetic approach, how basic ideas could be used in order to generate automatically a great numbers of strategies. Then we show some results of ecological evolution on those strategies, with the description of the experimentations we have made. Our main purpose is to find an objective method to evaluate strategies for the CIPD. Finally we use the former results to add a new argument confirming that there is, in order to be good, an infinite gradient in the level of complexity in structure of strategies. 1 The Classical Iterated Prisoner's Dilemma Introduced by Merill M. FLOOD and Melvin DRESHER in the RAND Corporation in 1952, see [3], who tried to introduce some irrationality in the game theory of John VON NEUMANN and Oskar MORGENSTERN [8], the Classical Iterated Prisoner's Dilemma (CIPD) is based on this simple story quoted by Albert TUCKER for instance in [5,...