In order to simulate nature, you need to have the mutation and selection process itself be part of the programs (and not the interpreter). How about you have a "world" consisiting of some memory, bombard this world with "cosmic radiation", and add some "enzymatic activity" in the form of an interpreter that interprets a location of the world as a simple language (that allows observation and modification of the world, as well as forking new threads of execution) - which is randomly started at random points. After some time, you might have threads that reproduce themselves, perhaps forming species, cooperation, pathogens, genders, and if you wait four billion years, civilizations... Life is really just core wars without the programmers :-) -k -- If I haven't seen further, it is by standing in the footprints of giants