286 I The Process of Evolution 



body of information that passed from generation to generation non- 

 genetically. It also seems highly likely that these protohumans 

 utilized a reasonably complex system of verbal communication. The 

 making of stone implements is not as simple as the twentieth-cen- 

 tury armchair observer might believe. While it is conceivable that 

 young Australopithecines learned to do this merely by careful 

 observation and mimicry, it seems more likely that a certain amount 

 of spoken instruction went along with the demonstration. The pos- 

 session of culture, and perhaps of speech, by these long-extinct, very 

 small-brained anthropoids clearly outlines the probable solution of 

 one of the most vexing problems in human evolution, the "cause" 

 of the roughly threefold increase in brain size between that of 

 earliest fossil man and modern man. 



As culture became important in prehuman society, genotypes 

 with the mental characteristics permitting optimal utilization of this 

 extragenetic information were more successful reproductively than 

 their less-well-endowed cohorts. Genotypes were favored that pro- 

 duced brains with the highest ability to associate, integrate, and 

 store incoming sensory data and to utilize these data in a manner 

 that enhanced the survivability of the genotype. This selection 

 pressure resulted in a trend toward great expansion of the cerebral 

 cortex and an increase in the number and complexity of the neuronal 

 systems necessary for "thinking and speech." It is not unreasonable 

 to assume that much of this increased volume is the result of a 

 premium being placed on storage capacity. Man's tremendous neo- 

 pallium is relatively more free from commitment to special sensory 

 and motor functions than that of other mammals. These "uncom- 

 mitted" areas may be presumed to be concerned with association 

 and memory. This presumption is supported by results obtained 

 from electrical stimulation of the brain in conscious patients under- 

 going brain surgery. For example, stimulation of the temporal lobe 

 may lead to the patient rehearing a complete symphony or reliving 

 an event of the distant past. When a human being is subjected to a 

 frontal lobotomy, his sensory and motor functions are relatively 

 unimpaired, but he becomes "irresponsible." 



There is a considerable body of literature on the reasoning power 

 of chimpanzees. On certain types of tests designed primarily to 

 evaluate human reasoning power, some "chimps" score higher than 

 many human adults. Indeed, as Harlow succinctly puts it, if man 

 is defined as the possessor of mental abilities that occur in other 

 animals only in the most rudimentary forms, if at all, we "must of 

 necessity disenfranchise many millions . . . from the society of 

 Homo sapiens." Chimpanzees may lack culture not because of any 



