EVOLUTION 123 



from the standpoint of natural selection. Un- 

 doubtedly the differences in the immunity to 

 various diseases characteristic of different hu- 

 man races are to be attributed to this kind of 

 influence. But that natural selection has been 

 the main driving force in the evolution of 

 man is no more to be admitted than it is in re- 

 spect to the other organisms. Natural selection 

 seems to be a real but subordinate factor in 

 organic evolution, the mechanism of which is 

 still to be discovered. 



In man much of his social practice tends to 

 reduce rather than to preserve the efficiency 

 of natural selection. In ancient times and in 

 primitive races to-day the malformed or other- 

 wise defective infant is often destroyed, thus 

 anticipating what is likely to happen later 

 through purely natural causes. With the 

 growth in our civilization of the sense of value 

 in human life, these practices have become 

 mostly illegal and have been largely sup- 

 pressed. As a result we have developed a large 

 body of institutions for the care of our defec- 

 tives, institutions supported by a strong pub- 

 lic opinion. Such social undertakings are in 

 direct opposition to the workings of natural 

 selection. They are a drain on the social body, 



