348 The American Naturalist. [April, 
Man is structurally different from all these. His arms are 
shorter as compared with his legs than in any of the existing 
large apes. It would be impossible for him to walk in the 
swinging manner of these apes, or by aiding himself with his 
hands like the gibbon. Quadrupedal motion on hands and feet 
would be almost equally difficult for him. If his ancestor was 
like him in this respect, as was undoubtedly the case, then on 
descending to the ground it must have been forced to walk on its 
feet alone, from the much greater difficulty, if not the impossi- 
bility, of the other modes of motion. 
man’s ancestor, however, became a biped through this 
necessity, it at once assumed a position of remarkable advantage, 
becoming the only species among the higher animals that did 
not have to use all four of its limbs in locomotion. His arms and 
hands were freed for other purposes, and the grasping powers of 
the hands added immensely to the advantages which this gave. 
In fact, there can be no question that man owes his supremacy in 
the animal world to the possession of two limbs which were free 
from duty as walking organs and could be used fully for attack 
and defence, and to the grasping power of his hands, which 
rendered easy and natural the employment of weapons. To this 
must be added the mental development which all known anthro- 
poid apes possess. These marked advantages at once changed 
his relation to the lower world of animals. Flight was no longer 
necessary to safety. He was able to meet much larger animals 
on equal ground. He was already, like all the apes, mentally 
acute, observing, and capable of foreseeing and providing for con- 
tingencies. As his power of walking erect became easy and natural, 
and the adaptation of his arms and hands to the use of weapons 
grew more definite, his standing in the animal kingdom essentially 
changed; fear and flight ended, so far as animal foes were con- 
cerned, retreat ceased, attack began, his mental acumen was called 
into active play, and the great battle for mastery of which we have 
spoken came fully into play. 
Still another essential element in this development was the 
social habit of man’s ancestor. If we may judge from the con- 
ditions of existing savages, the man-ape was a more social animal 




