The species category is defined as thesmallest historical individual within which there is a parental pattern of ancestry and descent. The use of historical individual in this definition is consistent with the prevailing notion that speciesper se are not involved in processes — they are effects, not effectors. Reproductive isolation distinguishes biparental historical species from their parts, and it provides a basis for understanding the nature of the evidence used to discover historical individuals.

The Linnaean system of classification is a threefold system of theoretical assumptions, sorting rules, and rules of nomenclature. Over time, that system has lost its theoretical assumptions as well as its sorting rules. Cladistic revisions have left it less and less Linnaean. And what remains of the system is flawed on pragmatic grounds. Taking all of this into account, it is time to consider alternative systems of classification.

The role of scientific theories in classifying plants and animals is traced from Hennig's phylogenetics and the evolutionary taxonomy of Simpson and Mayr, through numerical phenetics, to present-day cladistics. Hennig limited biological classification to sister groups so that this one relation can be expressed unambiguously in classifications. Simpson and Mayr were willing to sacrifice precision in representation in order to include additional features of evolution in the construction of classifications. In order to make classifications more objective, precise and quantitative, numerical (...) pheneticists limited themselves to representing degrees of phenetic similarity. Finally, present-day cladists can be separated into phylogenetic cladists, who retain much of Hennig's theory of classification, and pattern cladists, who have stripped Hennig's system down to its bare essentials. (shrink)

Mayr has made both conceptual and professional contributions to the establishment of the history and philosophy of biology. His conceptual contributions include, among many others, the notion of population thinking. He has also played an important role in the establishment of history and philosophy of biology as viable professional disciplines.