Page Four 



EVOLUTION 



April, 1929 



of the Old World are sharply distinguished frum the 

 apes and man by their cheek teeth, which definitely 

 jilace them as a specialized side line. They also retain 

 the primitive condition of the hind feet, in which the 

 main axis of weight passes through the third toe. 

 whereas in the apes and man it has been shifted to 

 the inner side of the foot. Professor Boule has sug- 

 gested that perhaps man separated from the Old World 

 monkey stock liefore the lengthening of the arms and 

 the shortening of the legs in the modern ape group ; 

 hut in view of the profound agreement of man with 

 the apes in brain characters, blood tests and fetal 

 development, a definitely pre-ape derivation of man 

 lacks substantial evidence. The principal objection of 

 deriving man from a point far down the primate tree 

 is precisely the lack at that early .stage of the very 

 numerous characters which connect the human stuck 

 with that of the apes. 



If the numerous converging lines of evidence fur 

 Darwin's view carry conviction to our minds, the next 

 quest'on is. when and where difl the separation take 



place ? As to the time when, the separation must plain- 

 ly have been before Mid-Pliocene times. The preced- 

 ing millions of years during which the apes were 

 branching out would seem to allow sufficient time for 

 the accelerated evolution when a marked change in 

 food habits, consequent U])on the invasion of the plains, 

 caused a higher instability in the ductless gland sys- 

 tem. If man is so derived, there is added reason to 

 search for his early representatives in some region of 

 open plains, not too far removed from the ancestral 

 forests of the conservative apes. 



Thus, as to place where the human stock began 

 to separate from the primitive chimpanzee - gorilla 

 group, we can reasonably expect to find it somewhere 

 with;n the known range of the ape group in the Mio- 

 cene and Pliocene periods, that is, somewhere between 

 Western Europe and Eastern Asia. Here we may 

 refer to the excellent analysis of this question by 

 Grabau and Black, who indicate the region of the 

 Tarim desert in Turkestan as the most likely place 

 in wh'ch to renew the search. 



Brains— How Come? 



Al.LAX STROXG BROM.S 

 VI 



THE brains of man. ape and mmikey are alike in shape 

 and workin.g parts. These near relatives of ours look 

 even more alike inside their skulls than outside. Man has 

 put in some recent improvements, but the ground plans are 

 the same. 



Viewed from the side, the human front brain looks like 

 a wrinkled boxing glove with padded thumb and knuckles. 

 From above it looks like the fat kernel of a walnut, in two 

 halves and all crumpled up. But it's not a "hard nut" nor 

 solid, its gray working surface being quite soft and thin. 



Mapping the working parts of the brain is simple in 



principle, but difficult in practice. To follow a nerve thread 

 from a brain center to the muscle it controls is some job, 

 l)ut just tickle the brain center and the muscle jerks, spot- 

 ting the connection at once. The brain surface is just uni- 

 formly gray, with nothing to label one part as sight center, 

 a second as touch center, and others for hearing, smell, 

 taste or for control over the various body muscles. But a 

 rap on the back of the head makes you see stars or go 

 blind, the sight centers being located there. Or an inside 

 blood vessel bursts over your ear and your arm is paralysed 

 or your speech gets all mixed up, the centers for the arm 

 muscles and for speech being located close together there. 



Strangely enough, the left half of the front brain is 

 connected with the right half of the body, and vice versa. 

 Then right arm paralysis means left brain injury. Most of 

 us. being ri.ght-handed, have certain brain convulsions larger 

 on the left, marking the greater skill of our right hands. 

 In left-handed people, this condition is reversed and our 

 early human ancestor (the Java ape-man) is known to have 

 been left-handed because his skull shows these right I)rain- 

 folds bi.gger. 



Our front I)rain is in halves because our body is in 

 halves, several of its sense organs (eyes. ears, nostrils and 

 touch) and its arms and legs being paired off right and left. 

 Our eyes today work together and blend their images in 

 the brain, but the eyes of our earlier ancestors worked 

 separately, watching on both sides. Even the most primitive 

 eyes could tell the directions of light or shadow by the 

 relative brightness from the two sides, and right now our 

 ears judge the directions of sounds that way. 



So our ape and monkey relatives have brains that ntatch 

 ours part by part. They have more smelling center be- 

 cause they need it more. We beat them, however, in having 

 bigger and better areas for our deep thinking, the so-called 

 "association" centers of our 'high-brow" frontal lobes. In 

 the last million years or so, since we left their ranks, this 

 expansion of the areas in which we put two and two to- 

 gether is our really big achievement. For these association 

 centers, with their added nerve connections, give us our 

 comparisons, judgments and general human wisdom, and 

 enable us to see deeper into the future, six jumps ahead 

 instead of just one. 



The next article "That Gray Matter We Brag: About."' 



