Pa(;e Four 



F. \' () L U T I O N 



j\L\RCH. 1929 



attempted a direct refutation of my arguments; they 

 have not shown wherein I erred either as to facts or 

 principles. They have simply made a flank attack by 

 citing admitted differences between men and apes. 



In these papers the evidence has been presented 

 for the following outline of the history of the primates. 

 By Basal Eocene times the primates were already in 

 process of differentiation from the tree-shrew stock, 

 which all authorities now regard as structurally an- 

 cestral to the primates. By Lower Eocene time> we 

 distinguish in both Europe and North America a 

 branch which culminated in the modern Tarsius. 



The structure of the hind foot is definitely known 

 in the representatives of the Eocene families, as well 

 as in all known recent and fossil lemurs. South Amer- 

 ican monkeys, Old World monkeys and apes, the hind 

 foot having a widely divergent great toe. with a flat 

 nail. Thus all the known palaeontologic, zoologic and 

 embryologic evidence supports the conclusion that 

 from their first appearance the Primates as an order 

 were thoroughly arboreal and that the terrestrial 

 habits of the baboons and of man are a later acquisi- 

 tion. The early human embryo also retains the marked 

 divergence of the great toe and even the adult human 

 big toe retains the broad flat nail of arboreal Primates. 



None of the lower groups— lemurs, tarsioids. South 

 American monkeys — approach man except in obvious- 

 ly parallel features. They all stand on a distinctly 

 lower plane and differ in many trenchant characters 

 which are discussed in the papers cited. 



The Old World series makes its api^earance in the 

 Lower Oligocence of Egypt. The most primitive 

 known form, Parapithecus, is structurally intermediate 

 between the stem of the tarsioids on the one hand, 

 and the whole Old World series on the other. Al- 

 though only the lower jaw is known, this highly im- 

 ]wrtant form must have had the shortened face and 

 the swollen braincase. and probably the large eyes, 

 of the small insectivorous tarsioids. Side by side 

 with it is the oldest of the true apes, the lower jaw 

 of PropUopltJiccus hacckdi. This has the dental 

 formula common to the Old World monkeys, apes 

 and man, but its lower jaw is deepened like that of 

 the fruit eating apes and its molars already fore- 

 shadow the Dryopithecus pattern of the apes and man. 

 It was plainly akin to the gibbons but smaller and 

 more primitive. The eminent anthropologist Sergi has 

 selected Propliopifhccus as an ideal ancestor of man, 

 but there is reason to believe that the human stem 

 did not split off so far down the line. The modern 

 gbbons have become specialized in the extreme length 

 of their limbs and in the sabrelike form of their upper 

 canine teeth, but they retain the hip callouses and 

 other primitive features that ally them both with the 

 Old World monkeys and with the anthropoids. Ac- 

 cording to Sir Arthur Keith's illuminating researches, 

 the modern gibbons have already effected the profound 

 readjustments of the internal organs necessary for the 

 upright posture habitually adopted Ijy the gibbon ; this 

 ape is no longer an arboreal quadruped but an upright- 

 moving ape; its internal organs are actually far nearer 

 to man than to the lowest of primates. 



In the Miocene and Pliocene of India and Europe 

 there was a wide spreading of the ape group, known, 

 it is true, chiefly from teeth and jaws, some of which 

 approach modern types. All develop the "Dryopi- 

 thecus pattern" of the molars, the renmants of which 

 are so clearly seen in man. 



In the lower primates the principal axis of weight 

 passes through the third or middle digit of the hind 

 foot; such animals run upon the branches like arboreal 

 quadrupeds. In the anthropoids the main axis of 

 weight is shifted toward the inner side of the foot, in 

 aflaptatlon to the grasping habit. In the secondarily 

 ground-dwelling mountain Gorilla the heel is broaden- 

 ed, the whole foot pressed flat upon the ground, the 

 toes relatively shorter and the great toe relatively larger. 

 In the human embryo of the ninth week the whole 

 foot recalls the ape condition and differs widely from 

 the adult foot, which doubtless for more than a mil- 

 lion years has become thoroughly adapted exclusively 

 for walking on the ground. 



Sir Ray Lankester, knowing well only the more 

 arboreal foot of the lowland Gorilla, endeavored to 

 cast doubt on the evidence afforded by the more ter- 

 restrial foot of the mountain Gorilla, and clings to the 

 belief that the peculiar construction of the human foot 

 still constitutes a bar to the derivation of man from 

 the anthropoid stem. Professor Adolph SchuIz, on 

 the other hand, has shown that during the course of its 

 growth the human great toe is at first distinctly more 

 ape-like and partly turned toward the other toes, but 

 that as development proceeds it becomes twisted on 

 its long axis so as to face downward, and is also 

 drawn in toward the other toes. To transform a gorilla- 

 like foot into a human foot, the big toe must uicrease 

 in length and rotate on its own axis so that its surface 

 shall he applied to the ground instead of facing to- 

 ward the other toes. Next it would lie necessary to 

 shorten still further the toe-bones and to narrow the 

 whole foot ; that is, to make all the toes parallel, and 

 tilt whole foot must be made to face downward rather 

 than inward. One might also say that in order to 

 transform an early embryo foot into the adult foot a 

 number of changes are necessary : to enumerate these 

 would be to repeat, word for word, the points of trans- 

 formation of the foot of a gorilla into that of man. 



The very fact that the great toe is the dominant one 

 is strong evidence for the view that the human foot 

 has been derived from an ape with a grasping great 

 toe, for no other known primates afford such a favor- 

 able starting point for the human condition. More- 

 over, the muscles of the human foot show convincing 

 evidence of special relationship to the anthropoid font, 

 as well vmderstood from the time of Fluxley. 



In view of all this and of the fact that man is tied 

 by so many other bonds to an order which was 

 thoroughlv arboreal in its first stages, the burden of 

 proof would seem to lie upon anyone who prefers to 

 maintain that the construction of the human foot con- 

 stitutes a serious obstacle to the derivation of man 

 from a pre-ape stem. 



( To I>c cniichidcd in our next issue. I 



