Sameness, novelty, and nominal kinds

Abstract

Organisms and their genomes are mosaics of features of different evolutionary age. Older features are maintained by ‘negative’ election and comprise part of the selective environment that has shaped the evolution of newer features by ‘positive’ selection. Body plans and body parts are among the most conservative elements of the environment in which genetic differences are selected. By this process, well-trodden paths of development constrain and direct paths of evolutionary change. Structuralism and adaptationism are both vindicated. Form plays a selective role in the molding of form.