A system can only improve/develop if selection acts on a self replicating system. So replication must precede selection. But how can a system reach a level of complexity so that it can self replicate, if it needs to have self replication to improve/develop itself through selection? A reaction loop will only go so far. An echo in a  canyon will bounce off a few times but it wont go on for millions of years.,(reply>), And even if self replicating and self improving systems are possible and therefore natural occurences in the universe, why do we not see other such systems around us that are not DNA-based cellular life?