47^ ZOOLOGY 



In all the ages of human history this civilization has been 

 growing more and more complex, and individuals are becoming 

 more dependent upon the common welfare. The more complex 

 these social organizations become the more are the points at 

 which they are open to destruction; and when they fail to 

 function, the more profound the destruction. These human 

 "civilizations" have risen and fallen much as species of animals 

 have, only much more rapidly. Now and again their totterings 

 have threatened to drag down the whole human social structure. 

 The recent world war is an illustration of this, — the best since 

 the middle ages. Nevertheless, thus far new groups of peoples 

 have always come to the front, have taken over the leadership 

 from those who have failed, and have modified,— in some ways 

 improving, — the political or economic program. As long as 

 there are new groups, outside the falling civilization, virile 

 enough to improve on the old, this waning of nations is not a 

 disadvantage to the species. Indeed all this may be a very 

 definite check upon the decadence of the species. Nevertheless 

 as the world is now being knitted together, it becomes less easy 

 to destroy one center of civilization without general disaster. 



From these considerations it is clear that man, as a species, 

 has two chances to fail where ordinary animals have only one. 

 Man, because the world is becoming more and more united into 

 one community, may fail in his artificially built up civilization so 

 profoundly as to jeopardize the species itself through the break- 

 down of our economic machinery. And, on the other hand, he 

 doubtless has within him that inner rhythm of advance and 

 decay which other species have shown. ' 



In spite of the fact that it is very doubtful if man has 

 improved organically in either a physical or mental way during 

 historic time, our curve of efficiency as a species seems upward 

 still, largely on account of our improvement in knowledge and in 

 social cooperation. We may reasonably expect this upward 

 trend to continue, unless it is broken prematurely by some vital 

 mistake and catastrophe in the conscious phase of our evolution, 

 as, for example, by misapplication of our scientific, social, 

 industrial or political knowledge and powers. 



The following seem to be some of the most likely factors 



