THE PROGRESS OF LIFE 93 



killed by means of pointed flint weapons, held in the 

 hand, and which he cooked by means of hot stones. 

 For even then man knew the use of fire. How he 

 advanced in knowledge, at first very slowly, and then 

 with ever increasing rapidity, is so extensive a subject 

 that it forms a separate branch of science, called 

 Ethnology, the facts of which form the foundation for 

 theories of the psychological evolution that commenced 

 with the advent of man, 



INFERENCES AND SPECULATIONS 



Proof of Evolution. From the foregoing very rapid 

 statement of facts it will be seen that palaeontology 

 shews clearly that the explanation of the order seen in 

 nature is to be found in the theory of descent with 

 modification. 



Suppose we take the horse as an example. The 

 evidence for its development from the five-toed 

 Phenacodus is clear ; this is connected through the 

 Condylarthra with the early carnivora, and these with 

 the primitive insectivora and polyprotodont meta- 

 theria. Then comes a break between the metatheria 

 and the prototheria ; but the latter are closely related 

 to the theriodont reptiles. Indeed, Professor H. G. 

 Seeley at first thought that Theriodesmus was a 

 mammal ; and it was only the discovery of Pareiasaurus 

 that proved both to be reptiles. But the theriodonts 

 form such a close connection between reptiles and 

 mammals that it is difficult to decide which of the two 

 to call them ; while they are also, in the lower forms, 

 related to the Amphibians. Between the Amphibians 

 and the fishes there is a considerable gap, as yet 



