On the possibility of constructive neutral evolution.
The neutral theory often is presented as a theory of "noise" or silent changes at an isolated "molecular level," relevant to marking the steady pace of divergence, but not to the origin of biological structure, function, or complexity. Nevertheless, precisely these issues can be addressed in neutral models, such as those elaborated here with regard to scrambled ciliate genes, gRNA-mediated RNA editing, the transition from self-splicing to spliceosomal splicing, and the retention of duplicate genes. All of these are instances of a more general scheme of "constructive neutral evolution" that invokes biased variation, epistatic interactions, and excess capacities to account for a complex series of steps giving rise to novel structures or operations. The directional and constructive outcomes of these models are due not to neutral allele fixations per se, but to these other factors. Neutral models of this type may help to clarify the poorly understood role of nonselective factors in evolutionary innovation and directionality.
Stoltzfus
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Department of Biochemistry, Dalhousie University, Halifax, Nova Scotia, B3H 4H7 Canada. arlin@carb.nist.gov
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D016798:Ciliophora / Q000235:genetics*; D019143:Evolution, Molecular; D020440:Gene Duplication; D017125:Genes, Protozoan; D007438:Introns; D008957:Models, Genetic; D008969:Molecular Sequence Data; D017393:RNA Editing; D012326:RNA Splicing; D016053:RNA, Protozoan / Q000235:genetics*; D017381:Spliceosomes / Q000235:genetics
D016053:RNA, Protozoan