Canalization in evolutionary genetics: a stabilizing theory?

Canalization is an elusive concept. The notion that biological systems ough t to evolve to a state of higher stability against mutational and environme ntal perturbations seems simple enough, but has been exceedingly difficult to prove. Part of the problem has been the lack of a definition of canaliza tion that incorporates an evolutionary genetic perspective and provides a f ramework for both mathematical and empirical study. After briefly reviewing the importance of canalization in studies of evolution and development, we aim, with this essay, to outline a research program that builds upon the d efinition of canalization as the reduction in variability of a trait, and u ses molecular genetic approaches to shed light on the problems of canalizat ion. BioEssays 22:372-380, 2000. (C) 2000 John Wiley & Sons, Inc.