ARBOREAL MAN 



Ancestors of the Human Stock Must Have Taken to the Trees at a Very Early 

 Period — Tree-dwelUng Habit Largely Responsible for the Success 

 of the Stock in Evolution — Man in Many Respects 

 Is Still Amazingly Primitive 



have taken to it after varying periods 

 of quadrapedal life. They have taken 

 to it too late to derive the full benefits 

 from it, for they took to it with the 

 fore-limbs already deprived of some of 

 their inherited mobility. Such animals 

 never become perfect tree-climbers. 

 They may acquire an extraordinary 

 skill in running about the branches of 

 trees, as many rodents do, or they may 

 even climb in the proper sense of the 

 word, but in this climbing the grip is 

 not obtained by the application of the 

 palmar surface of the hand, but by 

 the hook-like action of claws and nails; 

 this method is practiced by many of 

 the carnivora. The maximum of possi- 

 bilities is not attainable in any of these 

 cases." The power of grasp is all- 

 important. 



VALUE OF A HAND-GRASP 



"The power to grasp with the hand 

 and fingers seems such a very simple 

 accomplishment that it is difficult to 

 realize how such an apparently trivial 

 beginning can have produced the tre- 

 mendous changes that follow in its 

 train. The power of the hand-grasp 

 has made possible the forerunners of 

 the Primates, has perfected the evolu- 

 tion of the Primates, and paved the 

 way for the development of Man." 



After an elaborate discussion of the 

 anatomy of the forearm and hand in 

 man and various other animals, Dr. 

 Wood Jones says, "It would be a diffi- 

 cult matter to find the author who, 

 writing of the human forearm and the 

 human hand, has not seen in them the 

 very highest and most perfect develop- 

 ment of the animal kingdom. It has 

 long been customary to lavish praise 



' Arboreal Man, bv F. Wood Jones, M.B., D.Sc, professor of anatomy in the University of 

 London. Pp. 230, with manv illustrations. London: Edward Arnold, 1916; New York: Long- 

 mans, Green & Co., Fourth Avenue and Thirtieth Street. Price $2.40 net. 



531 



IT IS sometimes supposed that man's 

 ancestors acquired most of their 

 "human" characters at the time 



they began to walk upright. But 

 this supposition is not well founded. 

 The traits of the human race seem 

 largely to have arisen in the long period 

 during which the ancestral stock lived 

 in trees; and Dr. F. Wood Jones has 

 written an extremely interesting book 

 to point out some of the principal re- 

 sults of that arboreal existence.^ 



The evolution of the fore-limbs is one 

 of the most striking features of man's 

 progress. The legs of vertebrates are 

 probably developed from the fins of 

 fishes; and the earliest vertebrates, like 

 the water newt and salamander today, 

 doubtless had legs which served to 

 balance the body but were hardly able 

 to support it. A critical step was taken 

 when, as in the Therapsids and Thero- 

 morphs, legs developed enough to 

 walk on. To the primitive mobility 

 was added an essential stability. But 

 gradually the former had to be sacrificed 

 to the latter, and in most quadrupeds 

 the mobility of the fore-limbs long since 

 disappeared. In man, however, it re- 

 mains. The fore-limbs are not adapted 

 to walking on, as anyone can testify 

 who has tried to walk a hundred yards 

 on all fours. The question is : Did man's 

 ancestors ever walk on four legs, as 

 most animals do? It is impossible, says 

 Dr. Wood Jones, to believe that they 

 did. The arboreal habit saved them 

 from becoming quadnipeds, and there- 

 by enabled them to acquire supremacy 

 over all other forms of life. 



"The arboreal habit alone is not the 

 talisman; other mammalian stocks have 

 taken to an arboreal habit ; but they 



