When Food is Better than Sex: Messy Variations on the GA

Endosymbiosis, the extreme form of symbiosis where one symbiont is contained within the other, usually arises via parasitism or ingestion [Margulis, 1993]. This horizontal gene-transfer results in additional genetic material, from the point of view of either organism concerned. Sexual reproduction, in contrast, involves vertical gene-transfer, and implements the exchange of genetic material in a mutually exclusive manner i.e. the offspring has a mixture, rather than the sum, of genes from the parents. This paper compares three varieties of the Genetic Algorithm (GA), on a hierarchical building-block problem. The Simple GA utilises the usual sexual operators, cross-over and mutation, exclusively. The Messy GA [Goldberg et al, 1989] uses a ‘splice’ operator, that joins variable-length genotypes, in addition to the sexual operators. And, finally, a splice-only version of the Messy GA illustrates that sex is not always required, and can even be detrimental. Potential topic areas Evolutionary Approaches Coevolutionary approaches Collective and social behavior