174 EVOLUTION OF THE EARTH 



such a way that the opinion of each of five groups, namely 

 Americans, British, Teutonic Europeans, Latin Europeans, and 

 Asiatics, has equal weight. The agreement of the two maps 

 is surprising. It Indicates that at the present time the distribu- 

 tion of climatic energy and of civilization is almost identical. 

 Such differences as are discernible occur almost wholly where 

 exact information Is lacking or where the presence of Euro- 

 peans as colonial rulers raises the apparent standard of 

 civihzatlon. 



This brings us to the climax of our discussion. At the 

 beginning of this lecture we saw that human progress, that Is, 

 the growth of civilization, depends in apparently equal measure 

 upon inherent mental capacity, material resources, and energy. 

 We then saw that although inherent capacity has no relation 

 to present climatic conditions. It Is closely intertwined with 

 those of the past. We also saw that although some resources 

 like the metals and coal occur without respect to climate, their 

 utilization is largely controlled by climatic conditions, while, 

 the vast majority of resources depend directly upon climate} 

 through its effect on vegetation. Finally we have seen that] 

 human energy, even more than either of the other conditions, 

 appears to be dependent directly upon the physiological effect 

 of climate upon man's body. Thus In the evolution of civiliza- 

 tion, as in the broader field of the evolution of life, the most 

 obvious controlling factor, although by no means the only one, 

 appears to be climate. 



Steps in the Evolution of Civilization 



Invention of tools and speech, and discovery of use of fire. 

 In the light of this conclusion let us briefly examine some of 

 the great steps In the evolution of civilization. Three of the 

 earliest and greatest steps were the invention of tools, the In- 

 vention of speech, and the discovery of the use of fire. As to 

 the relation of tools and speech to climate, nothing definite 



I 



