1890. ] From Brute to Man. 347 
called again upon the resources of the mind, and a new era of 
intellectual evolution began. It is quite possible, as we have 
said, that the strain in the former case was equal to that in the 
latter. 
Not every animal is adapted by nature to such an evolution. 
Nearly every animal would be prevented from it by physical 
disadvantages. Even the anthropoid apes lack certain essential 
conditions of structure and habits, though favored by the forma- 
tion of their hands, and their power of grasping and using 
weapons. But of all animals, the species from which man 
descended seems to have been the best adapted, and far the most 
likely, to become the ancestor of a thinking being. For the 
mental evolution of man was due not only to his struggle for 
mastery, but also to special advantages which he possessed in 
the physical structure and the social relations of his ape ances- 
tor. Let us consider the former of these. We know that the 
ape family are fruit-eaters, and that trees are their natural 
habitat. But the larger apes manifest an inclination to descend 
to the earth, probably from their weight rendering a continual 
life in trees none too agreeable. The largest of them, the 
gorilla, dwells almost normally on the ground, and it is quite 
probable that this was the case with man’s ancestor. On the 
ground apes have to make certain changes in their method of 
locomotion. In the trees they move in a quadrupedal or in a 
semi-bipedal attitude, by crawling along the limbs, or by walking 
along the lower and clasping higher limbs with their hands. On 
the ground either a quadrupedal, a bipedal, or an intermediate 
motion must be assumed. The baboons, whose fore and hind 
limbs are nearly equal in length, have become quadrupeds.. The 
three principal species of anthropoid apes, in each of which the 
fore limbs are of considerable length, have adopted an intermediate 
mode of motion, swinging their bodies between their hands. The 
gibbon alone walks in an erect attitude, its very long arms 
enabling it to use its hands in walking without bending its body. 
All these animals are essentially quadrupeds, inasmuch as they use 
all four limbs in locomotion. The gibbon alone is somewhat 
inclined to walk as a biped, but not when moving swiftly. 
