LECTURES IN BIOLOGICAL SCIENCES 



hands were temporarily tree and no doubt were used to bring 

 objects close to the peripheral organs of vision, taste, and smell. 

 But something like a quantum jump is made when the hands 

 are continually tree for such activity in a bipedal animal like 

 Australopithecus. Then the arms and hands, chiefly under the 

 guidance of vision, become principal organs for interaction with 

 the immediate external environment. Catching food, eating, 

 grooming, fighting, toolmaking, and tool use become special ac- 

 tivities of the hands. 



These manipulations, accompanied by a rich flow of sense 

 data, including those from the more developed proprioceptive 

 arm-and-hand muscle sense, enlarge the flow of information to 

 the brain which, in turn, fosters development of association 

 areas for storage of past experience with the hands, and guides 

 and initiates new hand movements. The motor and sensory 

 projection areas are significantly expanded in the cerebral cor- 

 tex of primates with accomplished manipulation. 



The neural delay required when some extra-organic tool is 

 interposed between stimulus and response probably had much 

 to do with the further development of cognitive behavior in the 

 hominids and perhaps with the first ability to symbol and the 

 start of human language. We know that australopithecines car- 

 ried stones several miles to a living site, where these stones were 

 later made into designed tools. We infer that Australopithecus 

 carried these tools on trips away from the living site for use in 

 hunting. This sort of behavior implies thinking about things 

 that are remote in space and/or time. The australopithecines, 

 thus, furnish the earliest historical instance of displacement in 

 hominid behavior. The coadaptation of the hands, senses, and 

 projection and association areas in precise manipulations seems 

 a first basis for the subsequent development of human intelli- 

 gence. 



4. Carnivorous-Omnivorous Diet 



Food-getting behavior is, of course, a fundamental activity 

 of all animals. There is little doubt that modern man eats a 

 greater variety of food than most other living primates. The 

 chimpanzee and gorilla take mostly vegetable food. The chacma 



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