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 EVOLUTION

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EVOLUTION

analogies of structure and function in vastly different brain with all its convolutions and that of the orang

groups. Finally, the chief problem, which refers to teleology of adaptive modifications, is not even touched by the doctrine of descent from common ancestors.

(2) Man and the Anthropoids. — Paheontology knows of no records that point to the relationship be- tween the body of man and that of the anthropoid. Hence it follows that the argument of analogy and classification is of little worth. But, as ever and again attempts are made to discover analogies between every bone of man and the corresponding part of the ape (e. g. Wiedersheim). it will be useful to gather a few of the more important morphological discrepan- cies which exist between man's body and that of the anthropoids (orang-utang, chimpanzee, gorilla). It is, however, far from our intention to attribute to these differences any great argumentative force, espe- cially against those who suppose that there was a com- mon primeval ancestor from which both man and ape finally descend; nor do we wish to deny that zoologi- cally the human body belongs to the class of the mam- malia, nor that within this class there is any repre- sentative more similar to it than tlie anthropoids.

Of these differences the most important lies in the development of the brain of man and of the anthro- poid, which is seen from the comparison of the weights, .\ccording to Wiedersheim we are forced to jidmit that the relative mass of the human brain is twice that of the chimpanzee, while, alwolutely, it i.s from three to four times as great. The same is prol>- ably true of the orang-utang. while the brain of the gorilla, which, according to Wiedersheim, i,s the most humanlike of any of the aiitliropoid lirains, is rela- tively only one-fifth that of man's. The human skull is from three to four times as large as that of the an- thropoids. The difference becomes much more strik- ing still when wecompare the cerebral hemispheres and their convolutions. The weight of the brain of a male Teuton of from thirty to forty years of age i.s on the average 14'2 1 grammes, that of a female 127:i grammes, and that of a full-grown orang only 79-7 grammes (Wundt). The proportion is therefore from 1S:1 to 16:1. If we measure the superficial area of man's

we have, according to Wagner, from 1877 sq. cm. to 2196 sq. cm. for the human brain and 533-5 sq. cm. for that of the orang — that is a proportion of 44:1. It is further to be taken into consideration that, as Wieder- sheim points out, the hiunan brain is not to be looked upon as an enlarged anthropoidal one, hut as a " new acquisition with structures which the anthropoidal does not as yet [!] possess". These new acquisitions are presumably qualitative and refer mainly to the centre within the gi-eat cerebral hemispheres. Inti- mately connected with the development of the brain is the moderate development of the dentition of man in comparison with the chinless snout of the monkey, which is armed with powerful teeth. Again, "the human face slides as it were down from the forehead and appears as an appendix to the front half of the skull. The gorilla's face, on the contrary, protrudes from the skull, which on return slides almost entirely backwards from the face. ... It is only on account of its protruding, strongly developed lower parts that the small skull-cap of the animal can mask as a kind of human face" (Ranke).

A second group of differences is obtained by com- paring the limbs of man and the anthropoid. Owing to his upright stature, man's appendicular skeleton is quite different in form and structure from that of the anthropoid. This is shown not merely by the length of the single parts, which, strangely enough, exhibit inverse proportions, but also in the interior structure of the bones, as was proved l)y Walkhoff (1905) in the case of the femur. If we suppose the length of the body to be 100 we have, according to Ranke, the fol- lowing proportions: —

Part iCorillal Chimpanzee

Orang Negro

German

Arm and hand Leg

64-9 319

677 352

807 34-7

4516 4S-.5

45-43 48-8

Special measurements taken from the skeletons of an adult Frenchman and an orang, represented in

the accompanying plate, gave the following par- ticulars: —