The Ontological Status of Species as Evolutionary Units

Abstract

Reference to the species problem today might sound quaint and vaguely anachronistic. Perhaps the species problem was of some importance ages ago in the philosophical dispute between nominalists and essentialists or a century ago in biology when Darwin introduced his theory of organic evolution, but it certainly is of no contemporary interest. But’ species’, like the terms ‘gene’, ‘electron’, ‘non-local simultaneity’, and ‘element’, is a theoretical term embedded in a significant scientific theory. At one time the nature of the physical elements was an important issue in physics. The transition from the elements being defined in terms of gross traits, to specific density, to molecular weight, to atomic number was important in the development of atomic theory. The transition in biology from genes being defined in terms of unit characters, to production of enzymes, to coding for specific polypep-tides, to structurally defined segments of nucleic acid was equally important in the growth of modern genetics. A comparable transition is taking place with respect to the species concept and is equally important.