INTRODUCTION 15 



terns have been common, and the logical outcome of a 

 caste system is marriage between near relatives. Pride 

 of race encourages inbreeding among the ruling class, and 

 power within that ruling class prompts the perpetuation 

 of a serving class in the same manner. Why, then, should 

 exogamy have been continued so commonly throughout 

 epochs marked by rational thought and a high degree of 

 culture? It is true, there are exceptions to this general 

 rule. Rather intense inbreeding was practiced both in 

 Egypt and in Greece when they were at the height of their 

 power and influence. Nevertheless, exogamic customs 

 have prevailed. They exist in Europe and America at the 

 present day, and it is natural to wish to know whether 

 there is any biological justification for them. 



Let us propose three questions which will show the 

 sociological bearing of the problems under consideration. 



1. Do marriages between near relatives, wholly by rea- 

 son of their consanguinity, regardless of the inheritance 

 received, affect the offspring adversely? 



2. Are consanguineous marriages harmful through the 

 operation of the laws of heredity? 



3. Are hereditary differences in the human race trans- 

 mitted in such a manner as to make matings between 

 markedly different peoples desirable or undesirable, 

 either from the standpoint of the civic worth of the indi- 

 vidual or of the stamina of the population as a whole? 



Correct answers to these questions are a matter of 

 more importance than a superficial consideration indi- 

 cates. Settled in accordance with the biological facts, 

 they aid in establishing a concrete scientific basis for 

 marriage, divorce and immigration laws; they give 

 grounds for predicting the changes to be expected in the 



