AMUNDSON, R; Univ of Hawaii at Hilo: Why are developmental constraints “constraints”?

The study of developmental constraints is one of the enduring factors within the late twentieth century research traditions that grew into evo-devo. Developmental constraint has been fruitfully applied in a wide variety of contexts. For many years, an evolutionist�s position on the �adaptation versus constraint debates� was an important indicator of that person�s theoretical commitments. But constraint is, after all, a metaphor. Ontogeny can be seen to enable evolutionary change just as much as to constrain, restrain, or limit it. Why do we find developmentally-inclined evolutionists talking about developmental constraint rather than developmental enablement, or facilitation? It will be argued that the constraint-metaphor is a byproduct of the dominance of selectionist and adaptationist evolutionary theory during the second half of the twentieth century. Natural selection was conceived as a force (sometimes a �creative� force) that drove populations up the slopes of adaptive landscapes. With selection the productive force, few metaphorical choices were left for those who considered development to be an important aspect of evolutionary change. �Constraint� against the �force� of selection was the simplest way to get development into the picture. But times have changed in our understanding of the role of development in evolution. Must development still be seen as a constraint on evolutionary change? Reasons for and against the continued use of �developmental constraint� will be considered. The 1985 classic �Developmental Constraints and Evolution� (Maynard Smith, Richard Burian, et al.) will be reminiscently discussed.