Origin of Subfunctions and Modular Genes

Thursday, October 23, 2003 - 10:15am - 10:35am
Keller 3-180
Allan Force (Virginia Mason Research Center)
Evolutionary explanations for the origin of modular genetic and developmental pathways almost always invoke some sort of long-term selective advantage, e.g., as a functional prerequisite to the evolution of phenotypic complexity or as an enhancer of evolvability. However, simple theoretical results demonstrate that even in the absence of any direct selective advantage, genetic modularity can spontaneously emerge through the acquisition of new gene subfunctions. Provided that population size is sufficiently small, random genetic drift and mutation can conspire to produce changes in the underlying genetic architecture of a species without necessarily altering the phenotype. Extensive genetic modularity may then accrue in a near-neutral fashion in permissive population- genetic environments, potentially opening novel pathways to morphological evolution. These results provide additional support for the proposition that many aspects of gene and genome complexity in multicellular eukaryotes may have arisen passively as population size reductions accompanied an increase in organism size, with the adaptive exploitation of such complexity occurring secondarily.