510 THE CHANGING WORLD 



tats far apart, and are quite different in general appearance, although 

 unmistakably relatives. 



In conclusion may be quoted the eminent paleontologist, W. B. 

 Scott (1858- ), who says, "The main outline of the problem of 

 distribution has been satisfactorily explained on the evolutionary 

 theory, and no other theory even pretends to account for the facts." 



Evidence from Fossils 



It would be quite as impossible to describe Niagara Falls without 

 mentioning either water or honeymooners, as to write about evidences 

 of evolution from fossils without citing the remarkable known history 

 of the horse. Everyone is led to refer to this famous pedigree, 

 extending back for something like forty million years, because it 

 furnishes a perfect and well-authenticated demonstration of evolu- 

 tion. 



The earliest known "horse" was Eohippus, of which thirteen 

 species have been identified from the Eocene period. A full grown 

 Eohippus was scarcely more than a foot high. It had four toes and 

 a remnant of a fifth on each front foot, with three toes and parts 

 of a first and fifth on each hind foot. These feet were well adapted 

 for living on the soft ground of forest areas. The teeth of Eohippus 

 were piglike in character and not at all like the highly modified 

 teeth of modern horses. In fact, during Eocene times all the mam- 

 mals were in a decidedly primitive stage, not yet having become 

 differentiated into carnivores and herbivores, with corresponding 

 modifications of their teeth and general structure. 



If we now leap the intervening years and come down to the mod- 

 ern horse, Equus, we find a very different animal. Its adult size is 

 much larger. It is the only quadruped which, like a toe-dancer, 

 stands upon a shoelike hoof at the tip of a single toe on each foot 

 with its heel high off the ground. It is adapted for rapid flight over 

 open plains, for, since the days of Eohippus, carnivorous school- 

 masters have appeared to teach it how to run for its life. Its teeth 

 are unique. The molars are all practically alike, with high crowns 

 constructed in such a way, with hard enamel and softer dentine side 

 by side, that these substances wear away unequally, thus always 

 leaving sharp grinding enamel surfaces. Moreover, its teeth con- 

 tinue to grow for some years, instead of attaining maturity early in 

 life, and so are enabled to keep up the life long grind to which they 

 are subjected. 



