136 EVOLUTION AND SOCIAL PROGRESS 



decide. There are flaws in the chain of evidence, which re- 

 quire careful and detailed consideration. For instance, the 

 genus Equus (horse) appears in the upper Siwalik beds, which 

 have been ascribed to the Miocene age. It has, however, been 

 maintained that these beds are really Lower Pliocene or even 

 Upper Pliocene. It is clear that the decision of this question 

 is of the utmost importance. If Equus really existed in the 

 Upper Miocene, it ivas antecedent to some of its supposed 

 ancestors. 



Again, in the series of equine forms, Mesohippus, Miohippus, 

 Desmathippus, Protohippus, which are generally regarded as 

 coming into the direct line of equine descent, Scott points out 

 that each genus is, in some respect or other, less modernized 

 than its predecessor. 



In other words, it would appear that in the succession of 

 North American forms the earlier genera show, in some points, 

 closer resemblance to the modern Equus than to their immediate 

 successors. It is possible that these difficulties and others of 

 the same kind will be overcome with the growth of knowledge, 

 but it is necessary to take note of them, for in the search after 

 truth nothing is gained by ignoring such apparent discrepancies 

 between theory and fact. 10 



It is not as an attack upon the theory of evolu- 

 tion that these statements are quoted, for the pur- 

 pose here is neither to attack nor defend, but to 

 make plain the truth which has too often been 

 studiously overclouded. The fact is that nothing 

 can be known with certainty in this matter, even 

 where we are dealing with what is apparently the 

 most obvious evidence, as in the present instance. 



All that we can say is that the various clearly 

 distinct species appear abruptly in their geologU 



* "Student's Text Book of Zoology," II, p. 600. 



