Two empires or three?

In the last 100 years, several spectacular discoveries were made in the world of biodiversity, discoveries such as the Okapi in the Congo forest, the only living relative of the giraffes, or Latimeria in the Indian Ocean, a living coelacanth fish, believed to have been extinct for 60 million years. But these were merely small white spots on the world map of biodiversity. By contrast, Carl Woese’s discovery of the archaebacteria was like the discovery of a new continent. Where should one place this new group of microorganisms? From antiquity until the twentieth century, the traditional division of the living world was into animals and plants. Even today, biology is taught in zoology and botany departments in many colleges and universities, particularly abroad. Botany, for a long time, was defined as including anything living that is not an animal. As a result, the study of fungi and bacteria was assigned to botany departments. Indeed, in the nineteenth century, some of the leading bacterial taxonomists had their professorships in botany departments. The subdivisions within animals and plants were equally unbalanced. After 1859, the study of phylogeny produced great advances in our understanding of the relationship of animals. The recognition by Grobben (1) that “above” the coelenterates there are two major groupings of animals, the Protostomia and the Deuterostomia, was a great leap forward. The most important recent development, of course, was the use of molecular methods in the field of classification. Although usually confirming the results of morphological analysis, molecular methods are all-important in all cases of controversy and/or uncertainty. It is now only a question of time until the true relationship of all phyla and classes of animals is firmly established. Although foreshadowed by suggestions made by earlier authors, by far the most important advance made …