THE EVOLUTIONARY CONSTRUCTION OF MOLECULAR POLYMORPHISMS

Simple evolutionary processes can regularly generate events that appea r highly unlikely when compared to the universe of all possible events . Models incorporating this evolutionary dynamic we call ''constructio nist'' and we contrast them with traditional models which focus on sta tic, equilibrium aspects. In population genetics, constructionist mode ls have provided a different perspective on several long-standing prob lems. We review three examples of the results from our own work. These results are: (1) simple evolutionary processes can result in multiple -allele polymorphisms maintained by selection that are highly unlikely to occur if fitnesses are chosen simultaneously and at random; (2) th e frequency at which viabilities (e.g., heterozygote advantage or rece ssive lethality) occur in mutations is likely to be very different fro m that observed in established polymorphisms; and (3) the power of the Ewens-Watterson test of neutrality is low. Several extensions of the models are discussed, together with the sorts of questions they may an swer. We conclude that a complete understanding of the evolutionary fo rces responsible for molecular polymorphism requires consideration of its temporal development as well as examination of its current form.