LAWS CONTROLLING HUMAN SOCIAL HEREDITY 321 



one has a better education and better instruments to 

 work with than the other. Thus social heredity 

 explains the origin of the modern individual with his 

 peculiar characteristics and his extraordinary 

 mental grasp, so much superior to that of earlier 

 days, even though the substratum of innate charac- 

 ters out of which the individual has been produced 

 may perhaps be no greater than was possessed by 

 mankind three thousand years ago. To explain the 

 condition of modern civilization, then, there need 

 have been no great increase of brain power over that 

 possessed by man long ago, but simply the action of 

 that series of acquired characters which furnishes 

 man with new tools. The real advance has been in 

 the treasures heaped up by social heredity and not 

 in the organic nature of man. 



We thus easily understand the interaction of civil- 

 ization and intelligence. As the result of normal 

 variations individuals, and even races of men, have 

 appeared with more or less variable mental powers, 

 and these being due to internal factors are trans- 

 mitted by organic heredity. But although this may 

 be the explanation of the mental possibilities of the 

 twentieth-century newborn infant, it is not the ex- 

 planation of the great mental power of the twentieth- 

 century adult. The infant is from birth subjected 

 to the molding influences of the twentieth-century 

 environment, and this acting continually upon his 

 plastic mental nature produces finally an adult with 

 mental capabilities commensurate with the influences 

 that have been concerned in forming him. Hence 

 the higher the civilization the greater will be the 

 force of the influences at work to form the mind of 

 the growing child, and therefore the ability of the 



