14 BIOCHEMICAL SYSTEMATICS 



contribution, that of providing a biochemical basis for showing 

 relationships and ultimately the recognition and incorporation of 

 molecular evolution into the over-all, synthetic concepts of taxonomy. 



Phylogenetic concepts and taxonomic systems 



Crow (1926) has presented an excellent argument in defense 

 of phylogenetic approaches to taxonomy, the following exerpt being 

 typical: 



The relationships of organisms with one another are not theoretical 

 interpretations at all, but descriptions of the actual facts of the relation- 

 ship of parts of one organism to another. Phylogeny consists of theories 

 and hypotheses formed from these facts. . . . Phylogeny can give little 

 satisfaction to those who desire absolute truth, but those who hold a 

 partial view to be better than none at all may find it an interesting 

 study. 



Theories and hypotheses, essential to analytical science, 

 while often rejected ultimately in the light of unfavorable subsequent 

 evidence, are symbolic of progress, and failure of a new theory or a 

 new hypothesis to emerge is perhaps indicative not of vitality but 

 rather stagnation in that instance. No scientific discipline, unless it is 

 purely descriptive, can afford to discourage or impugn the erection of 

 rational hypotheses from available knowledge. Nevertheless, in sys- 

 tematic biology, which is an analytical science, those attempting to 

 erect phylogenetic systems of classification, particularly those treat- 

 ing groups at higher taxonomic levels, often must defend not only 

 their particular hypothesis, but even the utility of hypotheses per se. 

 Doubtlessly many of those who object to phylogenetic classifications 

 (Gilmour, 1961; Russell, 1962; and others) have, in part, acquired 

 such an attitude as a result of the multiplicity of differing systems 

 which have been proposed for particular groups. All of the systems 

 are stoutly defended by their proponents, and, among the compre- 

 hensive systems, all are constructed from more or less the same 

 available data. Even some taxonomists have argued that systematists 

 should not strive to arrange and classify plants on an evolutionary 

 basis but rather should classify only on the basis of total similarities 

 (such a system may be referred to as "natural" even though not im- 

 plicitly phylogenetic). However, such a position cannot possibly be 

 defended on philosophical or even pragmatic grounds, and the writers 

 consider it axiomatic that phylogeny is the intellectual forte of 

 systematics. 



