Artificial selection in a system of self-replicating strings

Increasingly, artificial life (AL) models are introduced to study various aspects of the formal foundation of the phenomenon of life. Metabolism and the ability to self-replicate have long been considered as the most prominent of these aspects. It is natural to ask, how AL-systems might be used in application problems of today. Since AL-systems are based on competition between entities, which brings about selection of some entities that are more adapted than others (provided there are differences at all among entities), an evident idea is to artificially select, for those entities that are useful from an outside perspective. We implement this idea in the context of a recently proposed simple model of self-replicating strings (W. Banzhaf, 1993). These strings form an ensemble called the string soup, in which they can encounter each other and react according to predefined reaction pathways to produce other strings. The system is self-organizing in that every string comes in two alternative forms its one-dimensional information holding string form, and in a second form, capable of operating on the first form of itself and of other strings. Thus, we exploit the physical identity between what is being organized (operands) and what organizes (operators) in order to ensure self-organization.<
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