CREATION BY EVOLUTION 



They were already true vertebrates, with the same main 

 divisions of the whole body as in man, the same ground plan 

 of the brain and spinal cord, the same type of segmentation 

 of the vertebral column, the same general type of complex 

 skull (to be described later) ; moreover, these ancient 

 Devonian iishes and their modern representatives agree with 

 early stages of the human foetus in the general plan of fhe 

 jaws and gill arches and in the basic features of the digestive, 

 circulatory, respiratory and reproductive systems. Hence the 

 humble dogfish or shark, which is a relatively little modified 

 survivor of the early vertebrates, is universally recognized by 

 biologists as affording a true ground plan of human anatomy 

 and physiology. 



"We do not know why the earliest fishes gave rise on the 

 one hand to a line of forms that progressed to ever higher 

 types and on the other hand to far more conservative ones, 

 including the existing sharks and ganoid fishes, which repre- 

 sent, on the whole, an arrested or retarded evolution; but the 

 fossil record of the vertebrates shows that in every geological 

 age one finds the more conservative, less modified descend- 

 ants of older stocks living contemporaneously with the far 

 more progressive relatives. The science of comparative 

 anatomy, in collaboration with allied branches of science, is 

 able to decipher the evolutionary history of man from the 

 vast mass of Nature's documents precisely because the more 

 conservative forms of each geological age enable us to visu- 

 alize the anatomical characters of older periods and to recon- 

 struct, with progressive approach to complete accuracy, the 

 steps by which the older conditions have given rise to the 

 newer ones. 



By lower Devonian time the vertebrate stock had already 

 split up into the following main groups: first, the ostraco- 

 derms, an excessively ancient group, of which nearly all the 



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