640 MAN AS A CONQUEROR 



from uncontrolled experiments in human matings already performed. 

 The evaluation of such data can be adequately handled only by means 

 of the elusive and illusive technique of statistical treatment. More- 

 over, the collection of facts about human beings is inevitably colored 

 and distorted by pride and prejudice. Plants and animals do not 

 tell lies about themselves, but some human beings do. 



The fact that here one more often deals with complex traits rather 

 than more directly with the elementary genes, and that the smoke 

 screen of training and education plays, in man, a particularly con- 

 fusing role by covering up the contrasting effects of heredity and 

 environment, makes the analysis of the human hereditary picture all 

 the more difficult. 



While there is no doubt that the fundamental laws of Mendelism, 

 which go so far to elucidate hereditary procedure in plants and ani- 

 mals generally, are equally applicable to mankind, they cannot be 

 subjected to the same demonstrable proof. Even the most ardent 

 disciple of eugenics would hesitate to propose the back-cross of a 

 man with his recessive grandmother in order to determine his genetic 

 constitution. 



The fact that a problem is difficult, however, does not mean that it 

 cannot be solved. The more difficult it is the greater the challenge 

 presented and the greater the final satisfaction when a successful 

 solution is eventually found. 



Biological Background of Eugenics 



In spite of obvious difficulties, a workable program of eugenics is 

 by no means a hopeless proposition, since biological science has 

 already furnished much solid ground for eugenics to stand upon. It 

 is quite definitely established, for example, that biological inheritance 

 in man, as in other organisms, depends primarily upon continuity of 

 the germplasm rather than upon somatic contributions acquired during 

 the lifetime of the parents, and that consequently any characteristic 

 which an individual possesses arises not from, but through, the bodies of 

 the parents from more remote ancestral sources. The parents, there- 

 fore, are to be regarded not as the source of the child's heredity, but 

 simply as the trustees and guardians of the hereditary stream whose 

 springs lie far back in the cloud-covered mountains of the evolutionary 

 past. 



Mendel has shown us how purity can arise from impurity, not by 

 any miraculous process of the "forgiveness of sins," but by the 



