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Show 140 THE DESCENT OF 1\rAN. PAl~T I. branches until the rind is eracked, and then tear it off with the fingers of the two hands. Other monkeys open mussel-shells with the two thumbs. With their fingers they pull out thorns and burs, and hunt for each other's parasites. In a state of nature they break open hard fruits with the aid of stones. They roll down stones or throw them at their enemies ; nevertheless, they perform these various actions clumsily, and they are quite unable, as I have myself seen, to throw a stone with precision. It seems to me far from true that because "objects "are grasped clumsily" by monkeys, "a much less " specialised organ of prehension " would have served them 62 as well as their present hands. On the contrary, I see no reason to doubt that a more perfectly cons~ructed han.d ~o~ld have been an advantage to them, provided, and It IS Important to note this, that their hands had not thus been rendered less well adapted for climbing trees. We may suspect that a perfect hand would have been disadvantageous for climbing; as the most ~rboreal monkeys in the world, name! y Ateles in Amenca and Hylobates in Asia, either have their thumbs much redu~ed in size and even rudimentary, or their fingers partially coherent, so that their hands are converted mto mere grasping-hooks.63 As soo~ as some ancient member in the great series of the Pnm. ates came , owm· g t o a ch ange m. I.t s manner o~ procun~g sub~istence, or to a change in the conditiOns of Its native country, to live somewhat less on tr.e es and more on the g roun d, I· ts manner of progres- SIOn would have been modified., and m. thI'S case I. t :: 'Quarterly Review,' April, 1869, p. 392. In Hylobates syndactylus as the nam rco-u]arly cohere. and th' ' M B ' e e.XJ)rcsses, two of the digits o ' IS, as r lyth i' · · the case with the di o-its of H ·z· · l t.. or~s me, 1s occaswnally o • agz 18, ar, and leuctscus • .._ --..- _..._ L .. - .. ~ .~ :.. .. -·- .. .s.a.~ - -- -~:r""":. ,. CIIAP. IV. MANNER OF DEVELOPMENT. 141 would have had to become either more strictly quadrupedal or bipedal. Baboons frequent hilly and rocky districts, and only from necessity climb up high trees; 64 and they have acquired almost the gait of a dog. Man alone has become a biped; and we can, I think, partly see how he has come to assume his erect attitude, which forms one of the most conspicuous differences between him and his nearest allies. Man could not have attained nis present dominant position in the world without the use of his hands which are so admirably adapted to act in obedience to his will. As Sir C. Bell 6ainsists "the hand supplies all instruments, and by its " correspondence with the intellect gives him universal " dominion." But the hands and arms could hardly have become perfect enough to have manufactured weapons, or to have hurled stones and spears with a true aim, as long as they were habitually used for locomotion and for supporting the whole weight of the body, or as long as they were especially well adapted, as previously remarked, for climbing trees. Such rough treatment would also have blunted the sense of touch on which their delicate use largely depends. Fro~ these causes alone it would have been an advantage to man to have become a biped ; but for many actions it is almost necessary that both arms and the whole upper part of the body should be free; and he must for this end stand firmly on his feet. To gain this great advantage, the feet have been rendered flat, and thegreat toe peculiarly modified, though this has entailed the loss of the power of prehension. It accords with the principle of the division of physiological labour,. which prevails throughout the animal kingdom, that 64 Brehm, ' Thierleben,' B. i. s. 80. 65 ''The Hand, its mechanism," &c. 'Bridgewater Treatise,' 1833,. p. 38. |