Vestiges of the natural history of development: Historical holdovers reveal the dynamic interaction between ontogeny and phylogeny

Abstract

Vestigial features of humans and other organisms are well known and have long been used as key evidence for evolution. Such features include not only anatomical structures but also physiological processes, biochemical reactions, and even behaviors. In addition to remnants of evolutionary change, traces of developmental change likewise exist, and it is important to distinguish embryonic remains from true evolutionary vestiges because people confuse evolutionary and developmental changes. To avoid confusion, the term vestige should be reserved for true evolutionary holdovers. This paper presents examples of developmental remnants, which often involve circulatory and reproductive alterations, and discusses numerous other retained or reappearing historical holdovers in ways that reveal the unfolding dynamic interaction between genotype and phenotype. These holdovers are useful in differentiating and relating concepts of phylogeny and ontogeny as well as revealing benefits of historical reasoning in understanding patterns and processes of organismal change.