326 GENERAL BIOLOGY 



nature for the human species is far too high for civilized 

 conditions. It was adequate to replace the losses by war, 

 pestilence and famine in primitive society. But now that 

 these agencies of death are in a measure controlled, the 

 natural balance is disturbed. Without these checks the 

 human population of the earth is rapidly increasing. 



Many wild species are being exterminated, and most of 

 them are being reduced in numbers. For man must carry 

 with him the few domesticated species on which his livelihood 

 depends, and wherever he spreads, the native population of 

 the earth must be annihilated to make room for his fields and 

 stock pens. The pressure for room has often been felt in 

 "congested districts" throughout human history. With 

 the present excess of birth rate over death rate, the whole 

 habitable earth will be one congested district soon. Every 

 triumph of science over plague or famine or other casualty 

 increases the pressure, so long as the excessive rate of in- 

 crease continues. 



The ideal condition of society is that toward which nature 

 points the way in the series of phenomena we have just been 

 studying: the adjustment permitting the normal well-condi- 

 tioned development of every individual. 



There are biological aspects of our civilization that 

 are not reassuring: 



1) The possibilities of the germ are realized only in the in- 

 dividual. Whatever the nature of it, only nurture can bring 

 it to perfection ; and nurture is still largely wasted among 

 us in broken lives. 



2) The weaklings of our race under existing conditions, 

 not only survive, but they usually survive to perpetuate 

 their weaknesses in descendants. 



3) There are processes of civilization that select the best 

 for elimination; wars, which kill off the strong and the 

 brave on the battlefield and leave the weak at home to 

 breed. And economic conditions that take the brightest of 



