THE MINGLING OF RACES 559 



adism, is one that has an hereditary basis. This has been 

 worked out in some detail by the author and the results of his 

 investigation have, so far, not been disproved. We have 

 evidence also that other instinctive quahties are characteris- 

 tic of the different races of mankind and have Hkewise an 

 hereditary basis. 



A race is more than a haphazard collection of individual 

 traits. Each well-estabhshed race which has persisted for many 

 generations in the same locahty has gained in the course of 

 these generations an adjustment to the particular environ- 

 mental conditions in which it Hves. This adjustment to 

 environment has been brought about in man by a different 

 method from that employed with domestic animals. A 

 breeder of dogs, let us say, finds a mutation which offers 

 certain advantages to the possessor for particular purposes. 

 He seizes upon this advantageous trait; succeeds in repro- 

 ducing it by breeding and then seeks to place the dog, or 

 the new breed of dogs, in a position where it can make use 

 of this trait. It will be observed that the new mutation is not, 

 from the beginning, better or worse, but it is better or worse 

 for a particular environment in which the animal is to be 

 placed. It remains, in order that the mutation should be 

 advantageous, that the dog should come to find an environ- 

 ment for which this new trait pecuharly fits it. Thus, in the 

 course of time, there have come into existence many races of 

 dogs which differ from each other in form or in temperament 

 or in instincts, and for each of these differences some niche 

 has been found which has made it possible to preserve the 

 particular strain of dogs as a useful race. 



So, also, in mankind the races that have survived have 

 been those which have become possessed of one or more 

 traits that have pecuharly fitted them for the environments 

 in which they arose or which have enabled the possessor to 

 find an environment in which the new traits would give 

 him a special advantage. The adjustment of races to their 

 environments depends first upon the possibiHty of mutation. 

 The experience of geneticists in the last twenty-eight years 

 has demonstrated that such mutations are constantly 

 present in all species of animals and plants. The problem is 

 no longer how^ mutations arise but rather how it comes about 



