The evolution of genetic networks by non-adaptive processes

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Abstract
Raises questions about the widespread belief that the structures of genetic networks are driven entirely by adaptive processes. Provides an overview of the empirical evidence for the evolution of novel regulatory mechanisms by neutral processes with little or no alteration at the phenotypic level. Provides a simple explanation, on the basis of amounts of intergenic DNA, of why multicellular species are more prone to the evolution of complex regulatory mechanisms than are unicellular species. Demonstrates that the effective size of a population alone can dictate the potential pathways of network evolution. Demonstrates that recombinational activation, and not mutational masking, is a powerful force for promoting redundant genetic pathways. Argues that models of network evolution that ignore intermediate states of population-level variation are incapable of providing meaningful insight into issues of pathway evolution.