The evolutionary construction of molecular polymorphisms

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Abstract
Simple evolutionary processes can regularly generate events that appear highly unlikely when compared to the universe of all possible events. Models incorporating this evolutionary dynamic we call “constructionist” and we contrast them with traditional models which focus on static, equilibrium aspects. In population genetics, constructionist models have provided a different perspective on several long-standing problems. 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) the frequency at which viabilities (e.g., heterozygote advantage or recessive lethality) occur in mutations is likely to be very different from 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 answer. We conclude that a complete understanding of the evolutionary forces responsible for molecular polymorphism requires consideration of its temporal development as well as examination of its current form.