Foundations and Methods of Evolutionary Classification

Abstract

Biological classification has always been concerned with expressing relationships between organisms, living and fossil, in a system that provided a foundation for further study and generalization. The foundations and mode of expression of the resulting classification have not always been the same. The Linnean hierarchy provided a formal scheme of ranking groups within groups, but the exact rules of the hierarchy depended on the accepted theory underlying biological classification. With the acceptance of organic evolution after 1859, the theory underlying classification modified from that of ideal typology to organic evolution. Yet the exact nature of classificatory schemes varied with the state of knowledge of evolutionary mechanisms and with the acceptance of diverse combinations of these mechanisms as crucial for biological classification. Thus all of the major modern approaches to biological classification are regarded as evolutionary, and the designation of one as classical evolutionary classification, or more simply as evolutionary classification, does not imply that the other approaches of phenetics or cladistics (phylogenetic classification) are not based upon organic evolution.