224 SOCIAL HEREDITY AND SOCIAL EVOLUTION 



can possibly find sustenance, it becomes clear that 

 the question of the struggle for existence as affecting 

 mankind is entirely different from that question as 

 affecting other animals. At the present time man- 

 kind is far from having reached the possible limits of 

 population. A great part of the surface of the world 

 which is perfectly able to support millions of human 

 beings is still unpopulated. Until man has multi- 

 plied so greatly as to have reached, or nearly 

 reached, the limit of population that can be supported 

 on the surface of the earth, he cannot be subject to a 

 struggle for existence such as that which actuates the 

 lower animals. 



Nevertheless, mankind is by no means freed from 

 this struggle, nor from the action of the law of nat- 

 ural selection. It is self-evident that those individ- 

 uals, those families, and those races that are not fitted 

 for their environment must either become fitted or 

 disappear, and mankind as well as animals must yield 

 to this inevitable law. The problems of human life 

 are vastly complicated by a great number of arti- 

 ficial factors if for no other reason. Man alone 

 has created artificial conditions, and with every suc- 

 cessive century these conditions undergo a modifica- 

 tion. The relation of mankind to the struggle for 

 existence is consequently undergoing constant 

 change. The problem as it affects the twentieth cen- 

 tury is a different one from that affecting the begin- 

 ning of the nineteenth century, or even the middle 

 of the nineteenth century. Comparing the problem 

 of man's struggle for existence to-day with the same 

 problem two thousand years ago, we find that the 

 conditions introduced by the artificial product which 

 we call society have been so confusing that few facts 



