EVIDENCE FROM DISTRIBUTION 137 



merely the existing distribution of its mammals, it 

 would be entirely possible to deduce from that dis- 

 tribution the main outlines of the history which 

 geology reveals. The geological dates could not be 

 so definitely fixed, but the principal events and the 

 order in which they occurred could be made out, 

 assuming the truth of the evolutionary theory. The 

 very fact that such an assumption is necessary, if 

 the deductions are to harmonize with the facts re- 

 vealed by geology and palaeontology, is strong evi- 

 dence that the assumption is true. On the theory 

 of special creation and the immutability of species, 

 the facts are meaningless. We find that a certain 

 proportion of South American forms is extremely 

 peculiar, having no close allies in any other conti- 

 nent, and a certain proportion is of mammals clearly 

 related to those which dwell in Arctogsea. But the 

 latter all belong to peculiar species and many of 

 them to peculiar genera, which, on this theory means 

 that they were separately created and therefore that 

 their relationships with North American and other 

 Arctogaean forms are purely ideal. It is highly sig- 

 nificant that the history, so far as it has been recov- 

 ered and deciphered, is seen to lead gradually through 

 a long series of changes to the present order, which 

 is so plainly the inevitable outcome of those changes, 

 provided only that evolution be accepted. 



It may well be asked why no such interchange of 

 mammals between the Americas is going on now, but 

 the question cannot be definitely answered. It is 



