134 EVOLUTION AND SOCIAL PROGRESS 



our discoveries, and we shall never be able scien- 

 tifically to establish all the data for the beginnings 

 of life. The earliest records, in fact, are almost 

 completely destroyed, like the writings that have 

 been effaced from a school-boy's slate, with but a 

 curve or a dot remaining, here or there. It is the 

 height of absurdity to speak of these questions 

 with apodictic certainty, where even guessing is 

 hazardous. 



One other fact must still be stated here, and 

 that is that the rocks of the earth themselves bear 

 no direct evidence of any evolution. The vari- 

 ous types, even among the early invertebrates in 

 the Cambrian formation, appear "clearly sepa- 

 rated into all the families and most of the classes 

 which exist at present." 6 The same is true of 

 the vertebrates. The fishes in the lower Silurian 

 formation appear just as clearly separated from 

 the invertebrates. "There are numerous quite 

 different types existing, but separate from the be- 

 ginning." 7 The first birds, though with certain 

 reptilian characteristics, cannot be shown to have 

 really descended from any particular reptile. The 

 earliest mammalia are clearly differentiated, and 

 we find them at the eocene period "almost as 

 fully typified and as sharply defined as today, par- 

 ticularly such as were of unusual size or of pe- 



!5W Frank> S ' J' " The Th eory of Evolution," p. 30. 

 I via. p. 31. 



