THE EVOLUTIONARY DYNAMICS OF SEX DETERMINATION

There is substantial cytogenetic data indicating that the process of s ex determination can evolve relatively rapidly. However, recent molecu lar studies on the evolution of the regulatory genes that control sex determination in the insect Drosophila melanogaster, the nematode Caen orhabditis elegans, and mammals suggest that, although certain sex det ermination regulatory genes have evolved relatively rapidly, other sex determination regulatory genes are quite conserved. Thus, studies of the evolution of sex determination, a process that appears to have ele ments that, undergo substantial evolutionary change and others that ma y be conserved, could provide substantial insights into the kinds of f orces that both drive and constrain the evolution of developmental hie rarchies.