Elliot Smith describes this stage of development as follows:(27) "... The emancipation of the hands from progression threw the whole responsibility upon the legs, which became more efficient for their purpose as supports once they lost their prehensile powers and became elongated and specialized for rapid progression. Thus the erect attitude became stereotyped and fixed and the limbs specialized, and these upright simians emerged from their ancestral forests in societies, armed with sticks and stones and with the rudiments of all the powers that eventually enabled them to conquer the world. The greater exposure to danger which these more adventurous spirits encountered once they emerged in the open, and the constant struggles these first semihuman creatures must have had in encounters with definite enemies, no less than with the forces of Nature, provided the factors which rapidly weeded out those unfitted for the new conditions and by natural selection made real men of the survivors." [Illustration: FIG. 40. Side view of brain of high type, illustrating the contrast between the motor, sensory, and ideational centres in a high type of modern brain; and Elliot Smith's characterization of the probable centres in the _Pithecanthropus_ type of brain. Modified after M. Allen Starr.] The undeveloped forehead of _Pithecanthropus_ and the diminutive frontal area of the brain indicate that the Trinil race had a limited faculty of profiting by experience and accumulated tradition, for in this prefrontal area of the brain are located the powers of attention and of control of the activities of all other parts of the brain. In the brain of the ape the sensory areas of touch, taste, and vision predominate, and these are well developed in _Pithecanthropus_. The central area of the brain, which is the storehouse of the memories of actions and of the feelings associated with them, is also well developed, but the prefrontal area, which is the seat of the faculty of profiting by experience or of recalling the consequences of previous responses to experience, is developed to a very limited degree.(28) Thus, while the brain of _Pithecanthropus_ is estimated at 855-900 c.cm., as compared with 600 c.cm. of the largest simian brain, and 930 c.cm. of the smallest brain recorded in the lower members of the human race, it indicates a very low stage of intelligence. [Illustration: FIG. 41. Diagram showing the side (lower figure) and top (upper figure) views of the outline of the _Pithecanthropus_ brain as compared with that of the chimpanzee and the higher human types of the Piltdown, Neanderthal, and modern races.] ABSENCE OF PALÆOLITHS AND PRESENCE OF EOLITHS IN WESTERN EUROPE