THE DUAL CHALLENGES OF NATURAL SELECTION: ACHIEVING STASIS AND OPTIMIZATION SIMULTANEOUSLY

Abstract

Students readily conflate evolution, gene-based change in organisms from one generation to the next, with natural selection. Natural selection is the main mechanism driving evolution, but these processes differ and the terms are not synonymous. A key point often overlooked is that in most situations, natural selection generally operates as a normalizing (stabilizing or optimizing) force that reinforces existing phenotypic variation. Paradoxically, natural selection usually works to prevent rather than promote evolutionary change. Relatedly, students often mischaracterize evolution as a drive for perfection. Natural selection is a normalizing yet optimizing process that does not yield optimal (ideal) design, but generates solutions just good enough to get by. This is because selection operates via elimination rather than addition, and because it works with existing phenotype rather than starting afresh. Thus, phenotypes often remain static and exhibit imperfections, ironically providing some of the best evidence for evolution.