Abstract Motivated in part by Ohno’s (1970) influential book, substantial attention has been given to the idea that gene duplication is a major mechanism for the origin of new gene functions. A theoretical population genetic framework for understanding the evolutionary mechanisms responsible for the success versus demise of gene duplicates has begun to emerge. Substantial evidence now exists that many of the key evolutionary lineages of multicellular eukaryotes have experienced one or more complete genome doublings (polyploidization) sometime in the distant past (Wolfe 2001), and the newly unveiled genomic sequences of diverse species clearly indicate that gene duplication is an ongoing process in all organisms.