correlation has been shown between brain size and intelligence. What advan- 

 tage was gained by the additional, apparently superfluous increase? 



He suggests an answer based on the growth pattern of the hominid 

 brain. For the modern child, the value of 750 c.c. is reached at the end of 

 the first year of life. According to Krantz: 



The child begins to use symbolic speech sometime during the following year, 

 usually at about 18 months, though he may understand it several months earlier. 

 It is here suggested that this minimum brain mass is just as necessary for the 

 symbolizing ability in the individual ontogeny as it is in the phylogeny of man. 

 While crossing the threshold does not guarantee speech if the nervous system is 

 not adequately developed, this threshold sets a lower limit below which symboliz- 

 ing is not possible. [Krantz 1961, p. 86] 



Krantz then proceeds to draw a hypothetical curve of brain growth for 

 H. erect us, setting the curve at a constant 61 per cent of the H. sapie?is curve. 

 The capacity of the Modjokerto child fits on this curve fairly well. The curve 

 shows that the endocranial capacity of H. erertus did not pass the threshold 

 of 750 c.c. until after the sixth year of life: 



Now, if the argument developed above is tenable, it is evident that the young 

 Pithecanthropus, prior to the age of about six years, clearly did not possess the 

 endocranial volume which appears to be a prerequisite for symbolization. Not 

 until the age of six did the Pithecanthropus brain approach the volume and com- 

 plexity of the brain of the modern one-year-old child. That this did in fact limit 

 the mental abilities of these children seems to be an inescapable inference. [Ibid., 

 p. 86] 



Allowing for errors in the reconstruction of the H. erectus growth curve, 

 the threshold crossing point could have been as low as four years or as high 

 as eight years. According to Krantz, this point has previously eluded students 

 of brain size, because juvenile capacities have been used thus far only as 

 guides to the probable capacities of the adult skulls. 



Increasing the size of the brain with the type of growth curve remaining constant 

 results in a proportionate increase of the brain at all stages of life. Any increase 

 thus moves the crossing of the threshold to a younger age. The advantage gained 

 by this brain expansion is not to be found in the adult size, but in the gradual 

 lowering of the age at which the children acquired the quantity of brain sub- 

 stance associated with symbolizing. 



The enculturation of the individual is considered to be primarily, if not 

 exclusively, based on the use of symbols. If the child lacks the ability to use and 

 understand symbols until the age of six, his enculturation will be about five 



Hi ^ 



