134 SOCIAL HEREDITY AND SOCIAL EVOLUTION 



unions are rarely very lasting. In most animals the 

 period of sexual excitement depends upon the season 

 and lasts only a few weeks. As this excitement 

 wanes the bond of union is apt to be severed and the 

 associations formed during the breeding season are 

 generally broken up at its close. Occasionally, it is 

 true, the unions may be more lasting, but it is the 

 exception for them to continue after the season of 

 sexual excitement is passed. With man, however, 

 these instincts are not limited to any season, but 

 serve as a bond for uniting the sexes in permanent 

 union. Whatever influence this instinct may have 

 had upon the family in later ages, it is unquestionable 

 that it was one of the primitive forces which pro- 

 duced the family, and has been one of the forces 

 which has kept the family institution in existence 

 during all the vicissitudes of the centuries, in spite 

 of all the attacks made upon it. The sexual instinct 

 must be recognized as one of the most potent influ- 

 ences, for both good and ill, underlying the develop- 

 ment of civilization. 



But this alone has not been sufficient to account 

 for the organization of the family. Among many 

 savage tribes the sexual passions are unbridled, free 

 indulgence is permitted, and there is no need of 

 family institutions for their gratification. Yet even 

 in these tribes the family is developjed. Hence the 

 permanent bond that unites the family cannot be 

 found in the sexual passion. The second force which 

 has contributed to the organization of the family is 

 the desire for a household and the possession of chil- 

 dren. This is based upon two emotions — love, or 

 affection, and pride. The latter is the lower and the 

 more primitive. The desire for a household must 



