552 THE CHANGING WORLD 



velopment of the projecting chin, and instead genial tubercles, small 

 s])ines of bone projecting backward for the attachment of the genio- 

 glossal muscles of speech, are present on the anterior inside angle of 

 the lower jaw, just in front of the spot which in tlie a\)OH is the loca- 

 tion of the simian shelf. As Professor Hooton remarks, "The slang 

 expression 'chinning,' meaning 'talking,' seems to have a certain 

 evolutionary justification," but it is not enough, however, to possess 

 the anatomical machinery for speech. A parrot has that. There 

 must be cortical centers developed in the brain sufficient to make 

 possible the realization of the significance of what is said in speech. 

 Many animals are vocal and make a variety of sounds. It is said 

 that chimpanzees have a vocabulary of at least a dozen words by 

 which they express various emotions. Dogs can modify their bark- 

 ing to indicate different things, and crows modulate their "caws." 

 No animal except man, however, puts together even a short sentence, 

 and there can be no such thing as an animal grammar. 



Skeletons in the Pleistocene Ice Chest 



When did man become human? How long has it been since he 

 emerged from among his nonhuman relatives to occupy a definite 

 place on the evolutionary stage? Research and discovery in recent 

 years have made it possible to give a tentative answer to these ques- 

 tions, which would not have been the case a century ago. There is 

 no doubt as to the existence of contemporary human beings all about 

 us, for they fall within personal observation. Tradition and his- 

 torians are able to carry back the story of humanity, with diminishing 

 certainty, through the Dark Ages at least to classical times. Beyond 

 that period the uncertainty deepens, even when persistent archae- 

 ologists with their spades uncover buried cities, often built one above 

 the other, and thus push back still further the outposts of human 

 antiquity. The builders of these ancient cities fade from view, 

 so far as archaeologists are able to inform us at present, about 

 5000 B.C., and when the thread is again picked up some 5000 years 

 earlier, that is, about 10,000 B.C., it is the vanishing prehistoric traces 

 of cave-dwellers which tell of the existence of man. Such troglodytic 

 evidences of man are spread over a long indefinite interval of time, 

 during which the ancestors of modern man probably endured a 

 precarious existence, limited to life in small, struggling, isolated family 

 groups. How to dwell together in anything like larger co-operative 

 relationship had not yet been learned. 



