Os dinossauros de Hennig: sobre a importância do monofiletismo para a sistemática biológica

Abstract

Biological systematics is the branch of natural sciences that deals with nomenclature, description, and organization of biological diversity in hierarchical schemes. It has been developed since the human first efforts toward the summarization of biological information in order to group organisms in classes, and to identify, among them, which ones are natural entities. From Aristotle to Hennig, many forms of systematizing the biological knowledge have been proposed, with the intention of delimiting and representing the natural affinities among organisms. Even after Darwin-Wallace's theory, biological systematics presented few changes in its foundations until the works of the German entomologist Willi Hennig. He introduced a method that was as objective and explicit as phenetics, and deeply connected to the Darwinian evolutionary perspective. Hennigian phylogenetics aims to create a classificatory reference system which reflects evolution. In this sense, Hennig proposed that only monophyletic groups are natural ones, since they were the unique that really respects the evolutionary concept of common descent. A monophyletic group is defined as the reunion of all descendants of a common ancestor, including it. Based on the recognition of monophyletic (natural) groups, the phylogenetic systematics is a powerful tool to reconstruct the evolution of the organisms with objective and scientific criteria, helping to solve the problem of systematizing the biological information that has worried mankind since the dawn of language.