Are Species Really Individuals?

Hull, David L. (Department of Philosophy, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201) 1976. Are species really individuals? Syst. Zool. 25:174–191.—The processes which contribute to the evolution of biological species take place at a variety of levels of organization; e.g., genes give rise to other genes, organisms give rise to other organisms, and species give rise to other species. All of these processes require continuity through descent. If species are to be units of evolution, they need not be composed of similar organisms; instead they must be made up of organisms related by descent. Taxonomists do not impose this requirement on the phenomena; rather it follows from the nature of the evolutionary process itself. In addition to spatiotemporal continuity, species must also possess a certain degree of unity to function as units of evolution. Gene exchange is one means by which such unity can be promoted. The mechanisms by which asexual species maintain a similar unity are problematic; higher taxa pose an even more serious problem. However, if species are chunks of the genealogical nexus, they cannot be viewed as classes. Instead they possess all the characteristics of individuals—that is, if organisms are taken to be paradigm individuals. The major difference between organisms and species as individuals is that organisms possess a largely fixed genetic makeup which constrains their development, whereas species do not. If species are individuals, then their names are most naturally viewed as proper names, names which denote particular individuals but do not possess any intensional meaning.