Eukaryotism, Towards a New Interpretation

Abstract

The phylogenetic-comparative molecular approach has caused a fundamental conceptual change in the way we view living matter. The new approach is based on the consequent utilization of genotypic comparisons, thus bypassing the limitations of phenotype. It differs in this respect fundamentally from the previous attempts of classification of life by Haeckel (1866), Chatton (1938), Copeland (1938), or Whittacker (1969). The approach rests on the decipherment of the genetic code, the development of potent strategies for nucleic acid sequencing, and on the assumption that each change per se, and its perpetuation, alteration, or relationship to other changes in an information-storing molecule, as in genomes in general, represents a phylogenetic event and is thus a direct record of evolutionary history. Consequently, sequence analysis may be expected to provide the means by which phylogeny may be deduced and-refined and complemented by analysis of the evolution of functions and structures-allow a global genealogical system to be established, i.e. to permit all lifeforms to be classified and related to each other, since any organism can be related to any other, unambiguously and quantitatively, and the properties of organisms can be understood in the context of their relatives. This has now been generally accepted, replaces the previous view in textbooks, and has resulted in a fundamental conceptual change in the thinking of biologists. Although even central aspects are still the subject of critical debate (see, e.g. Doolittle 1996; Martin 1996), it is highly probable that the approach will ultimately lead to a natural, coherent, and universal tree of life.