Orthogenesis and Evolution

Abstract

-In the panbiogeographic evolutionary synthesis, orthogenesis is referred to as a process which involves an inherent tendency to vary in certain directions, as ancestors vicariate or break apart into descendants. Orthogenesis has origins in the studies of form, but is given a biogeographic perspective in panbiogeography. The panbiogeographic use of orthogenesis is compatible with the origin of the term as presented by Haacke and Eimer. Misinterpretations of orthogenesis describing it as mystical, teleological and linear are invalid. The orthogenetic aspect of evolution was recognized by Darwin as laws of growth, but was neglected in favor of natural selection. Although an internal component to evolution is recognized by contemporary biologists, it is often considered to be secondary to natural selection. Where recognition is given to an internal tendency for evolution to proceed without requiring the action of natural selection, terms such as constraints, bias, and potential may imply orthogenesis. [Orthogenesis; panbiogeography; biogeography; vicariism; evolution; dispersal.] The orthogenetic idea that evolution has its own inexorable internal momentum forcing lineages beyond the limits of natural selection is obviously absurd [Dawkins and Krebs, 1979:507]. In due time all theories defending orthogenesis were refuted [Mayr, 1982a:530]. I can accordingly understand that some naturalists may wax religious, and speak of orthogenesis in mystical terms; others indulge in philosophical abstractions in regard also of the same orthogenesisions in regard also of the same orthogenesis etc. Naturally, I do not see the need for my part to follow in their company, but I do believe that, whatever we intend and believe, we had all better be clear about the substances here in play [Croizat,