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12
Evolutionary Studies
The evolutionary studies of this chapter have both practical and theoretical
interest. On the one hand, there are many controversial questions in evolu-
tion theory and the simple genotype/phenotype system of gene expression
programming can give us some insights into natural evolutionary processes.
On the other hand, evolutionary computation not only inherited all the con-
troversial questions from evolution theory but also created some of its own,
casting more shadow than light into evolution theory.
In this chapter we are going to discuss three fundamental questions of
evolution theory: (1) genetic operators and their power; (2) the importance
of the initial diversity; and (3), the importance of neutrality in evolution.
Furthermore, related to these fundamental questions, are several other perti-
nent questions that have been around for a long time in evolutionary compu-
tation and are here clearly answered in an empirical way. Such questions
include, among others, the role of sex, the role of building blocks, and the
problem of premature convergence.
12.1 Genetic Operators and their Power
Everybody agrees that, by and large, evolution relies on genetic variation
coupled with some kind of selection and, in fact, all evolutionary algorithms
explore these fundamental processes. However, there is no agreement con-
cerning the best way to create genetic variation, with researchers divided
between mutation and recombination. This fact per se is extremely reveal-
ing, suggesting that existing artificial evolutionary systems are fundamen-
tally different from one another. Indeed, artificial evolutionary systems are
themselves still evolving and among them, camouflaged by different repre-
sentations, can be found simple replicator systems, rudimentary genotype/
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