CHAPTER XX 



The Tests of Evolution 



I 



THINK there is more misunderstanding about evolu- 

 tion among laymen than about any other subject. Of course 

 we know that some fundamentalists still deny it. I am not 

 writing for them, but rather for those who have been led 

 to beUeve that the whole subject is settled and that "scien- 

 tists know all about it," which is quite untrue. The results 

 of evolutionary processes are everywhere easy to see, but 

 the situation is really like that of the man who sees a trolley 

 car for the first time. The route it has followed and the 

 direction in which it is going are clearly to be seen, and 

 the rate at which it progresses is obvious. But what makes 

 the thing move? 



Take such a stock as that of the horse, where the fossil 

 evidence is unusually good. Practically every single grada- 

 tion from the Uttle fox-terrier-like animal of thirty milUon 

 years ago to the present-day horse may be followed with 

 infinite elaboration of detail. The horse had its origin in the 

 New World and we know when it moved from the New 

 World to the Old, where it persisted in the form of the 

 zebras, wild asses, and wild horses of Tibet. The skeletal 

 remains show that horses, as we use the word today, existed 

 in Florida down to perhaps 10,000 years ago in unbeHevable 

 numbers. Then they died out. Why they died out remains 

 a mystery. The Spaniards brought horses with them from 



