210 ADAPTATION AND PROGRESS 



provided the physiological correlate of the psychical change we 

 are endeavoring to explain and we find many different anatomical 

 factors championed as the most important. Darwin stresses 

 erect posture and prehensile thumb; Heineman holds that the 

 mutation which made erect posture possible was in the ento- 

 cuneiform bone and position of the foramen magnum, and that 

 this change, forcing man from the tree life of his ancestors, left 

 him at so great a disadvantage in the struggle for existence that 

 success was possible only by the use of the little intelligence he 

 possessed to outwit his rivals, this necessity and use determining 

 the whole succeeding order of his evolution; 1 others, on the con- 

 trary, hold that the development of the intellect came first and 

 led to a new mode of life in a new environment and that this fur- 

 nished the occasion for physiological variations and the selection 

 of those that were especially serviceable. Delay in the closing of 

 the sutures of the skull was an important factor, 2 so too, were the 

 development of the apparatus of speech, the organ of speech 

 located by Broca in the third frontal convolution of the brain, 3 

 the nervous connection between the organ and the apparatus, the 

 development of the cerebrum, and the free use of the forearms 

 made possible by erect posture and terrestrial life. 



Approaching the problem from the standpoint of psychology 

 we have two lines of study, the first using the comparative method 

 with the endeavor to find the differential psychical element be- 

 tween man and beast, and here the power of abstraction and 

 association of ideas seems at present to be most stressed; and 

 second, the method used by Baldwin and others, of observing the 

 steps in the child's mind by which the transition is made from 

 reflexive and instinctive activity to that which is self-conscious 

 and purposeful. 



From the sociological point of view we have a study of the 

 materials furnished by the development of civilization as a whole, 

 of separate groups and of contemporary social movements, by 

 means of which we are able to analyze the social factors that 

 enter into the transition. 



1 The Physical Basis of Civilization, p. 31. 



2 Keane, Ethnology, ch. III. * Macnamara, Human Speech, ch. X. 



