U38O IATION ill 



bers of any i-n.l to become mm. ami more alike; 



social types are created and extreme <m from the 



i type is discouraged or even punished. Thus 

 there evolves out of the maturing experience of inter- 

 stimulation and response a social and nften highly con- 



kl .selection, which t'-nds to preserve the api 

 type and operates to expel or exterminate the extreme 



The growing volume of stimuli to intellectual develop- 



and the enn-tantly increasing selective value of 



mind, tended to bring internal adaptations in the form 



of more complex orirani/ation of the brain and nervous 



system. "A slower development of the individual and 



a longer infancy necessarily resulted. The prolong 



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 portion and the 



specialized use of th. limbs. A relatively long 



period of lactation, with inability to use food requiring 



. must have elianired the facial angle and 



-ion of the countenance.*' 



Mutual aid at* - highest development in the ani- 



mal kingdom amnni: the social apes and monk* 

 operation must have been further develop! among the 

 cave men, for we h. fs of their successful warfare 



against such imposing antagonists as the mammoth and 

 the cave bear. Hut there are forms of cooperation 

 other than united action against enemies. There is co- 

 i in seeking amusement and diversion. Play 

 tends to become organized in games and festivities. 1 n 



.tiding*, Principle*, p. 229; M* note at chapter *d. 



