there is an allometric relation between a dimension and its standard devia- 

 tion and on Pineau's (1965) finding that the parameters fluctuate according 

 to the nature of the measurements. "In the case of cranial capacities, a linear 

 relation appears if the standard deviations proposed by Tobias are put into 

 logarithmic co-ordinates." The slope of the line indicates that "the variabil- 

 ity of cranial capacity increases faster than the absolute value of this measure- 

 ment." Olivier has redrawn the allometric line using his own estimate of 

 1366 c.c. and 150 c.c. for the mean cranial capacity and standard deviation, 

 respectively, of modern man. This permits him to read off standard devia- 

 tions for the australopithecines (48 c.c), Homo habilis (63.8 c.c), H. erectus 

 of Indonesia (91.2 c.c), and H. erectus of China (114.8 c.c). To compute 

 population parameters, he considers that it would be injudicious— because 

 the S.D. values are imprecise— to use the mean ±3 S.D.s. "It is sufficient to 

 use the mean ±2 S.D.s to cover the normal biological variation, including 

 95 per cent of the subjects." By this method, and employing the mean capac- 

 ities I published in 1968, Olivier arrives at the following variation ampli- 

 tudes of hominid cranial capacities: 



Population Mean Range 



Australopithecines 500 c.c. 405-600 c.c 



Homo habilis 639 c.c. 510—770 c.c. 



"Pithecanthropus" 880 c.c 700-1060 c.c 



"Sinanthropus" 1075 c.c. 845-1305 c.c 



Modern man 1 ^ f 7° cc - 1070-1670 c.c. 



Classic Neandertal 1470 c.c. 1145-1795 c.c. 



six 



id CRANIAL CAPACITY FROM 



Q AUSTRALOPITHECUS TO HOMO SAPIENS 



Cranial capacity and hominid taxa 



We have been led to conclude that the most startling jumps in brain 

 size occurred with and after the emergence of H. erectus. The jump from 

 the A. africanus mean of 494 c.c. to the H. habilis mean of 656 c.c. is of 

 the same order of size as the jump from the mean for the Indonesian 

 group of H. erectus (859 c.c.) to the Pekin group of H. erectus (1043 c.c). 



& 96 



