EVOLUTION OF THE III' MAX HAND. 465 



A life amid its branches is compatible with a condition of weakness 

 or deienselessness which would be fatal to the species under the circum- 

 stances of a ground habitat. To descend from the trees and venture 

 that mode of life implies one of three possible resources: the animal 

 must either he Heel of foot enough to distance his pursuers, or he 

 must possess weapons of defense sufficient to repel attack successfully, 

 or, finally, he must supply deficiencies in these regards through a 

 cunning which enables him to escape his enemies by artifice. The apes 

 are not swift of foot as compared with heasts of prey. They are poorly 

 provided with natural weapons or means of defense. They have 

 neither tusks nor claws, neither hoofs nor horns, neither great mass 

 and strength nor impenetrable hides. If they are to take the aggressive 

 or even to repel attack successfully it must be by the invention of 

 artificial weapons whereby their deficiencies are made good; but as 

 recourse to such instruments is a purely mental resort to obviate actual 

 physical difficulties, it may be said that the ape-man met his difficulties 

 in only one way, namely by cunning — escaping his enemy by retreat 

 to strongholds of his own devising; meeting him, when battle was un- 

 avoidable, not with bare hands but with weapons, and taking his prey 

 by traps and snares. But the schemes of his cunning brain could 

 become practicable only as the result of a distinct mechanical construc- 

 tiveness. Stones must be gathered and dropped or thrown with ac- 

 curacy ; clubs must be selected and wielded ; traps must be put together 

 after they have been devised. In all this the manipulative hand is 

 essentially linked with the resourceful mind. With any other known 

 type of limb the problem would have been insoluble. The special- 

 ization of the hand, therefore, with its opposable thumb and its won- 

 derful adaptability to mechanical uses we may conclude to have been 

 the single indispensible condition, so far as regards gross anatomical 

 features, which determined the widely divergent subsequent fortunes 

 of the monkey tribe and man-ape respectively. 



For the principle of separation between this type and the rest of 

 the anthropoid apes we must look to the different directions of develop- 

 ment taken by the central nervous system in the two cases. Henceforth 

 no important structural changes are to occur in the general features 

 of the hand. Development is to take place chiefly through an increase 

 in the facility and precision with which a variety of relatively simple 

 movements are made, and the substitution, in ever increasing grades of 

 complexity, of mechanical instruments for the use of the hand itself 

 as a manipulative and constructive agent. 



VOL. i.xv. — 30. 



