3 3O E VOL UTION OF TO-DA Y. 



judging by results, it amounts to a difference greater 

 than any other distinction found among animals. 

 What could have been the cause of this remarkable 

 development in this one case alone ? As an explana- 

 tion we have offered to us natural selection, together 

 with the suggestion that when intelligence had 

 become enough advanced to create language, prog- 

 ress would be very rapid. But this explanation 

 appears to most people entirely insufficient to 

 account for such a development, even supposing the 

 development possible. Natural selection seems in- 

 adequate anywhere, and it certainly seems so here. 

 It has produced this result in no other case, although 

 the intelligence of other animals than primates indi- 

 cates that there was equal foundation for advance 

 elsewhere. It must assume that chance produced 

 the beginning of intellectual advance in the human 

 ancestors, and by chance Darwin simply means an 

 unknown cause. Here, as elsewhere, even if evolu- 

 tion be a fact, its explanation is yet undiscovered. 



Another point must be mentioned as of great sig- 

 nificance, though we might not find all scientists 

 agreeing. It is, however, a growing conviction 

 among scientists that evolution is not unlimited. 

 There has been in all ages a growth from the general 

 to the special. An unspecialized form is capable of 

 very great development in numerous directions, but 

 as soon as it becomes highly specialized in any one, 

 the development practically ceases. A pocket-knife 

 is a generalized instrument, and may be used for 

 almost any purpose from cutting down trees to 

 carving images. It is capable of modification in 



