344 RAYMOND J. NOGAR 



and good phyletic sequences of origins have been established by 

 scientific prehistory. This series includes the fossil evidence 

 for some structural development of homo sapiens. The only 

 available natural explanation which does not conflict with the 

 natural processes which are manifest in geology and neo- 

 biology is the evolutionary one, common descent with modi- 

 fication. 



On the infra-specific level, Ford's field work on the moth 

 and the selective forces at work in modifying the species sup- 

 ports the concept of natural modification in species and varie- 

 ties; Dobzhansky's work (and others) on Drosophila give con- 

 vergent support to the theory of common descent with modi- 

 fication from the standpoint of mutation of genes and the sur- 

 vival of such mutation within the population. On the generic 

 level, the amazing series of freshwater molluscs Pauludina can 

 be traced in a single 300 foot deposit: nine species with more 

 and more complicated shells emerge from one smooth-shelled 

 species. Equally significant is the same kind of evidence found 

 in English chalk of the Micraster (sea urchin) series. On the 

 Family level, the Equidae (horse) series elaborated by Marsh 

 and Simpson is most striking. Twelve to fifteen genera of 

 horses can be traced with convincing dialectic and fossil docu- 

 mentation from the Eocene period, 60 million years ago, to the 

 present living genus, Equus. Similar studies, though not quite 

 so convincing perhaps, have been made among the ammonites, 

 camels, swine, crocodiles and fishes." 



Taken singly, any one series is established with the use of 

 a scientific methodology which is vulnerable to the stringent 

 rules of demonstrative logic. Yet, remembering the singular 

 nature of the problem of origins and the only methods natural 

 science has at its disposal, it is not certain demonstrative proof 

 that we are after, but that high degree of convergent proba- 

 bility which produces conviction and removes all reasonable 

 doubt. 



^' Cf. Dodson, op. cit., and especially, the symposium Genetics, Paleontology 

 and Evolution, ed. by Jepson, Mayr and Simpson (Princeton, 1949) , 



