GENERAL ZOOLOGY 



the classification of mankind in the family Hominidae, closely allied to the 

 family Pongidae, or tail-less apes; the fossil record of prehuman and early 

 human types; and the differences between the existing races of man — all point 

 to an evolutionary process as the single reasonable explanation of the facts. 

 Paleontological studies indicate that the order Primates, including man, apes, 

 monkeys, and lemurs, arose from the generalized early mammalian stock. 

 Fossil remains of prehuman races in more recent geologic time give evidence 

 of the line of man's descent. Taken as a whole, the evidence for human 

 evolution is entirely comparable with the evidence for the reality of animal 

 evolution in general. 



The structure of the human body is fundamentally like that of other 

 mammals and resembles particularly closely the anatomy of members of the 

 family Pongidae. This family includes the four types of tail-less apes: gibbon, 

 orangutan, gorilla, and chimpanzee (see Fig. 18.35, p. 586). There is no 

 essential detail of human anatomy that is not present in these apes, although 

 the more erect posture of man has been correlated with characteristic 

 specializations of the pelvis and viscera, the fore limbs, the foot, and other 

 parts. The brain, of course, is the most distinctive feature of man; with few 

 exceptions the brain of man is relatively larger than that of any other 

 vertebrate. On the whole, the specialization of functions in the human brain 

 exceeds that in any other mammal; but the structural and functional 

 specializations of the human cerebrum are all approached, though not 

 equaled, in the higher apes. The psychological characteristics of these apes 

 also resemble those of man. The evidence justifies the conclusion that the 

 ancestors of man advanced to articulate speech, to the development of greater 

 powers of reasoning and insight, and to the perfection of the hands as organs 

 of precise manipulation. Another line of descent, which produced the tail- 

 less apes, failed to progress in these respects to the extent characteristic of 

 the human evolutionary stock. 



A large number of vestigial structures in adult anatomy, and of primitive 

 characteristics in embryonic development, serve to link man to lower 

 vertebrate forms. Vestigial gill slits and a fish-like circulatory system are 

 formed in human embryos, as they are in those of other mammals. A tail 

 develops in the embryo but becomes vestigial in the adult; at one stage of 

 embryonic life the entire body is covered with a well-developed coating of 

 hair. The great anatomist Wiedersheim enumerated at least 180 vestigial 

 structures in the human embryo. There is no more logical explanation of 

 these facts than the assumption that they indicate evolutionary descent from 

 more primitive forms of life. 



Evidence from Fossils and Artifacts. The remains of human and 

 subhuman beings discovered in Africa, Java, China, Europe, and Palestine 

 give further evidence of the evolution of man.. In many instances only 

 fragments of skulls and of the larger bones have been found, but for certain 

 types complete skulls and even entire skeletons have been discovered. The 

 collections increase slowly year by year, but fossil remains of the earliest 



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