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Show 142 THE DESCENT OF 1\IAN. PART I. as the hands became perfected for prehension, ~ the feet should have become perfected for support and locomotion. With some savages, however, the foot has not altogether lost its prehensile power, as shewn by their manner of climbing trees and of using them in other ways.66 If it be an advantage to man to have his hands and arms free and to stand firmly on his feet, of which there can be no doubt from his pre-eminent success in the battle of life, then I can see no reason why it should not have been advantageous to the progenitors of man to have become more and more erect or bipedal. They would thus have been better able to have defended themselves with stones or clubs, or to have attacked their prey, or otherwise obtained food. The best constructed individuals would in the long run have succeeded best, and have survived in larger numbers. If the gorilla and a few allied forms had become extinct, it might have been argued with great force and apparent truth, that an animal could not have been gradually converted from a quadruped into a biped; as all the individuals in an intermediate condition would have been miserably ill-fitted for progression. But we know (and this is well worthy of reflection) that several kinds of apes are now actually in this intermediate condition ; and no one doubts that they are on the whole well adapted for their conditions of life. Thus the gorilla runs with a sidelong shambling gait, but more commonly 66 Hacke! has an excellent discussion on the steps by which man b~~me a ~1ped =. 'Nattirliche Schopfungsgeschichte,' 1868, s. 507. Dr. ~Ltchn er ( Conferences sur la Theorie Darwinienne,' 1869, p. 135) has giVen good cases of the use of the foot as a prehensile or.,.an by man · ~tlso on the n;tanner of progression of the higher apes to whlch I allud; lD t~~. followmg par~graph : see also Owen ('Anatomy of Vertebrates,' Yol. m. p. 71) on th1s latter subject. C UAP. IV. l\IANNER OF DEVELOPMENT. 143 progresses by resting on its bent hands. The longarmed apes occasionally use their arms like crutches, swinging their bodies forward between them, and some kinds of Hylobates, without having been taught, can walk or run upright with tolerable quickness; yet they move awkwardly, and much less securely than man. We see, in short, with existing monkeys various gradations between a form of progression stricti y like that of a quadruped and that of a biped or man. As the progenitors of man became more and more erect, with their hands and arms more and more modified for prehension and other purposes, with their feet and legs at the same time modified for firm support and progression, endless other changes of structure would have been necessary. The pelvis would have had to be made broader, the spine peculiarly curved and the head fixed in an altered position, and all these changes have been attained by man. Prof. Schaaffhausen 67 maintains that "the powerful mastoid processes of the human skull are the result of his erect position;" and these processes are absent in the orang, chimpanzee, &c., and are smaller in the gorilla than in man. Various other structures might here have been specified, which appear connected with man's erect position. It is very difficult to decide how far all these correlated modifications are the result of natural selection, and how far of the inherited effects of the increased use of certain parts, or of the action of one part on another. No doubt these means of change act and react on each other : thus when certain muscles, and the crests of bone to which they are attached, become enlarged by 67 "On the Primitive Form of the Skull," translated in' Anthropological Review,' Oct. 1868, p. 428. Owen ('Anatomy of Vertebrates,' vol. ii. 1866, p. 551) on the mastoid processes in the higher apes. |
