EVOLUTION OF MAN 223 



Old World monkeys and apes, as contrasted with New World monkeys, in 

 having a narrow nose, with nostrils close together, in having two premolar 

 teeth (instead of three) on each side of both jaws, in having a bony 

 canal connecting his external ear with the middle ear, and in numerous 

 other features. Man and apes lack an external tail; most monkeys of the 

 Old World have tails, although the latter are frequently more or less 

 shortened and in any event never develop the prehensile capabilities of the 

 tails of New World monkeys, which serve as veritable fifth limbs. 



In many ways man is similar in structure to the great apes, particularly 

 to the chimpanzee and the gorilla. Clearly, none of these forms are the 

 ancestors of any of the others, for they are all contemporaries. The 

 chimpanzee and gorilla are as completely "modern" in their own ways 

 as man is in his. They may be our distant cousins; they are certainly not 

 our grandparents. One's cousin is not one's ancestor. 



Granted that modern monkeys, apes, and men are related, how close are 

 the relationships among the several groups, and when did the evolutionary 

 line leading to each begin to diverge from the evolutionary lines leading 

 to the others? Unfortunately the fossil record is most incomplete on these 

 points. Fossils are few and fragmentary. And the very fact that similarities 

 among the forms in question are so great renders interpretation and evalu- 

 ation of fossil remains difficult. We should not be surprised, therefore, 

 that specialists in the field disagree sharply. In the present state of knowl- 

 edge dogmatic statements are not in order. Our wisest course is to present 

 the points on which there is general agreement and to state the bases 

 of disagreement on questions still undecided. In so doing we shall be 

 reflecting the fact that science itself undergoes continual evolutionary 

 change. Much of its fascination lies in the challenge of the still un- 

 answered questions. 



Fig. 11.2 presents in diagramatic form some of the best current thinking 

 concerning the evolution of Old World monkeys, apes, and man. The 

 diagram may be likened to a river flowing from bottom to top and dividing 

 into numerous channels as it progresses, like a river flowing through its 

 delta. At the bottom of the diagram we note the Eocene prosimians 

 mentioned above; from them arose the Oligocene ancestors of Old World 

 primates. New World monkeys are not shown; New World and Old 

 World forms may have originated from different groups of Eocene 

 prosimians, but we must await discovery of additional fossils before we 

 can be sure of relationships involved. 



In the Oligocene period the diagram includes a most interesting little 

 fossil known as Parapithecus. This creature is known from a single lower 

 jaw, less than two inches in length, found in Egypt. This tantalizing fossil 



