THE LIFE OF MAMMALS 
Man is distinguished from his fellow-Primates mainly by his 
erect walk, the roundness of his skull, caused by the indrawing 
Man asa and general lessening of the face, and by the ex- 
Primate. pansion above and behind the ears of the brain 
case; by his power of articulate speech; and by the absence of a 
hairy covering. This statement takes no account of that vast 
superiority of mind which chiefly distinguishes him; but it 
may be noted here that the differences in size and complexity 
of the brain — the seat of the mental faculties — between him 
and the greater apes are no greater than exist between some 
men and other men.’ 
As to his faculty of speech, that seems a mental accomplish- 
ment rather than a physical peculiarity, largely due to early 
men having caught the idea of making and using articulate 
sounds, and having perfected the art by practice. The vocal 
organs in the human throat do not differ materially from those 
of other vertebrates, nor are they remarkably advanced in per- 
fection. The shape of the human mouth and teeth, the more 
refined form and mobility of the lips, tongue, etc., undoubtedly 
aid in controlling the voice, and in pronunciation of sounds 
that have become the symbols of ideas, and therefore must be 
imitated exactly and repeated on demand. The ability to do 
this depends, however, on the possession of an educated ear, 
as is plain from the fact that persons totally deaf are also speech- 
less, although their vocal organs are perfect, and may be 
taught to pronounce words; and one who has not a fair sense 
of melody in his car is usually unable to learn to sing. 
Nearly all of man’s physical peculiarities are the result of his gradually 
acquired erectness, which has caused his spine to assume an elastic, S-like 
curve, rounding out at the shoulders and in at the waist, which forms a sort 
of spring, easing the jar of stepping or jumping, and also makes a better 
brace for exerting the strength of the limbs, while it adds flexibility to the 
body. The pelvis, greatly broadened, falls into an upright position, so as 
to bring the legs directly under the trunk, whose weight they must support 
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