Table 1 1: The relationship between coefficient oj variability (V) 

 and mean cranial capacity 



n Mean capacity (malrs) V 



Gibbon (H . lar) 95 L04.0 7.22 



Chimpanzee 163 398.5 9.76 



Orangutan 203 434.4 9.19 



Gorilla 414 534.6 10.67 



Modern man 1000s ca. 1345.0 12.57-14.87 



In relation to biological variables in general (Simpson, Roe, and 

 Lewontin i960, pp. 89-92), the values of V for gibbons, chimpanzees, and 

 orangutans are high, while gorilla and man, with Vs over 10.00, must be 

 considered markedly variable. 



On the available samples of capacities, living hominoids sort them- 

 selves into 2 categories, those with high variability and those with marked 

 variability. The 2 categories coincide with a sorting based on mean capacity: 

 the high-variability group have mean capacities for males of 435.0 c.c. and 

 below, while the marked-variability group have mean capacities for males 

 of 535 c.c. and over. Somewhere between 435 and 535 c.c. there would seem 

 to be a dividing line between highly variable and markedly variable capac- 

 ities in living hominoids. . 



The variability of cranial capacity in Australopithecus. Where does 

 Australopithecus lie? The mean capacity of A. africanus is 494 c.c. according 

 to my calculation based on published estimates, 430 c.c. according to Robin- 

 son's, 442 c.c. according to Holloway's based on new estimates, and 450 c.c. 

 based on my re-computation of Holloway's data. But the scanty data on 

 which these means are based do not permit us to determine whether A. afri- 

 canus belonged to the high-variability category or to the marked-variability 

 category. Robinson's (1966) choice of gorilla and modern man as guides to 

 the variability, and hence to the upper value, of cranial capacity in A. afri- 

 canus is therefore seen to be rather arbitrary and, indeed, unjustified, the 

 more so as his revised estimate of 430 c.c. for the mean capacity in A. afri- 

 canus is almost identical with the mean capacity in orangutan, and closer to 

 that of the chimpanzee than to those in gorilla and modern man. 



The population estimate of V for Australopithecus africanus, based on 

 an S.D. estimated from the range, gives a value of 8.4 per cent. This lies 

 amid the values for the high-variability group. However, as Holloway has 



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