FACT OF EVOLUTION TO THE PHILOSOPHY OF EVOLUTIONISM 345 



With the paleontological record objectively before us, and 

 the series of simpler forms to the more complex appearing in 

 distinct periods of space and time, let us see how all the disci- 

 plines of neo-organic science contribute buttressing, yet diver- 

 gent, arguments in support of common descent with modifica- 

 tion. Again, limited space allows only a schematic summary. 

 In biogeography, the area which was so convincing to Darwin, 

 we find biogeographical realms, discontinuous distribution and 

 exological zones. Within the local areas, we find marvelous re- 

 semblance and adaptation to the particular environment. These 

 singular conditions can best be explained by common descent 

 with modification. How else can the distribution of distinct 

 species of finches on the various islands of Galapagos be ex- 

 plained, species which so closely resemble the genera of finches 

 on the South American mainland.'^ 



In taxonomy, the classification of plants and animals, a mar- 

 velously delicate hierarchical relationship is manifested, just 

 what would be expected from common phylogenetic descent 

 with modification. As Darwin had put it " the only known 

 biological explanation for close similarity in nature (among 

 organisms) is common descent." ^® This statement is not uni- 

 versally true, as more recent studies have shown,^*^ but the 

 argument is dialectically sound and weighty. Taxonomic rela- 

 tionship is best explained by common descent with modification. 



A similar convergent argument is contributed from the mor- 

 phological sciences, e. g. anatomy and physiology. A study of 

 the organ systems of animals manifests a phyletic prototype 

 which is varied from class to class, family to family, etc. These 

 homologies and analogies are best explained by common de- 

 scent with modification. In embryology, the student finds that 

 individuals of different species (e. g. the hog, calf, rabbit and 

 man) pass through embryological stages which are almost 

 identical, a fact which is best explained by common decent 



** The Origin of Species, Chapter XIV (6th ed.; Modem Library) , p. 320. 

 *^ The trend called " parallel evolution " is described in Simpson's Life of the 

 Past, pp. 127 ff. 



