ASSOCIATION 111 



bers of any society tend to become more and more alike ; 

 social types are created and extreme variation from the 

 approved type is discouraged or even punished. Thus 

 there evolves out of the maturing experience of inter- 

 stimulation and response a social and often highly con- 

 scious selection, which tends to preserve the appreciated 

 type and operates to expel or exterminate the extreme 

 variate. 



The growing volume of stimuli to intellectual develop- 

 ment and the constantly increasing selective value of 

 mind, tended to bring internal adaptations in the form 

 of more complex organization of the brain and nervous 

 system. "A slower development of the individual and 

 a longer infancy necessarily resulted. The prolongation 

 of infancy, in its turn, must necessarily have effected 

 great changes in anatomy and physiology. A long 

 period of helplessness, by delaying the use of arms and 

 legs in ancestral ways, must have contributed to those 

 changes that resulted in the upright position and the 

 specialized use of the fore limbs. A relatively long 

 period of lactation, with inability to use food requiring 

 strength of jaw, must have changed the facial angle and 

 the expression of the countenance/' 11 



Mutual aid attains its highest development in the ani- 

 mal kingdom among the social apes and monkeys. Co- 

 operation must have been further developed among the 

 cave men, for we have proofs of their successful warfare 

 against such imposing antagonists as the mammoth and 

 the cave bear. But there are forms of cooperation 

 other than united action against enemies. There is co- 

 operation in seeking amusement and diversion. Play 

 tends to become organized in games and festivities. In 



11 Giddings, Principles, p. 229. 



