HISTORY AND NATURAL HISTORY 49 



of intersexual or family relations. This subject will 

 be discussed in more detail in the final chapter. 



The conclusion seems inescapable that the more 

 closely-knit societies arose from some sort of simple 

 aggregation, frequently, but not necessarily, solely 

 of the sexual-familial pattern. Such an evolution 

 could come about most readily with the existence 

 of an underlying pervasive element of unconscious 

 co-operation, or automatic tendency toward mutual 

 aid among animals. 



In the simpler aggregations evidence for the pres- 

 ence of such co-operation comes from the demon- 

 stration of survival values for the group. These are 

 more impressive the more constant they are found 

 to be. If they exist throughout the year they are 

 much more important as social forerunners than if 

 present only during the mating season or at times 

 of hibernation. 



