Scott Collins discusses the contraint of crossover with the male/ female partition and dominance. This is theoretically interesting, especially to biology. I know of no theoretical proof that such constraints improve the search of choppy search spaces, and there is little empirical evidence -- this is a cutting-edge research topic. The poster who first brought up sexual reproduction was discussing it in terms of its cutting and pasting of strings: crossover. Crossover itself provides a far more general solution than simple mutating, hill-climbing algorithms; specifically GAs are better in choppy, non-continuous spaces. The empirical evidence for this is quite substantial (the literature on GAs) and there is theoretical substantiation (Holland, Goldberg, et. al.). Perhaps constraining with male/female and dominance provides even further improvement for some kinds of choppiness, as might (more generally) demes, but those are open research questions in the GA community, not immediately germane to the general question of whether GA might be useful for cryptanalysis. I'd like to hear more about the male/female partition and dominance -- on comp.ai.genetic, ga-distr, or genetic-programming which I read regularly, and are much more appropriate for discussing this issue. Nick Szabo szabo@netcom.com