having just erupted. Its individual age would have been at least three or 

 four years younger than that of Old. Horn. 5 (A. boisei). Thus, whereas 

 it was not deemed necessary to allow for a correction factor in the latter 

 specimen, whose third molars are erupting but have not quite reached the 

 occlusal plane, in the case of Old. Horn. 7 such a correction should perhaps 

 be made. 



Growth data on living hominoids. There is a dearth of data for other 

 specimens of the same dental age. Selenka is quoted by Zuckerman (1928) 

 as stating that after the eruption of the second permanent molar in the chim- 

 panzee the capacity was 94 to 97 per cent of the adult size; unfortunately, 

 this was apparently based on only 4 skulls. The average capacity for 

 Zuckerman's 7 chimpanzees at the "intermediate stages" was 97.5 per cent 

 of the adult. This intermediate stage is not, however, confined to ages 

 after eruption of the second molars but covers all specimens between those 

 showing "milk teeth plus first permanent molars" to the stage designated 

 "third molar unerupted." Hence, Zuckerman's "intermediate" group 

 may have included individuals younger than the type specimen of H. 

 habilis. 



Ashton and Spence (1958) used a somewhat differently defined "inter- 

 mediate stage." The lower limit for their intermediate category seems to 

 have been exactly the same as that used by Zuckerman (1928). That is, 

 the skulls must have more permanent teeth than the first molar (and, in 

 the case of man, possibly also more than the permanent central incisors). 

 However, the upper limit differs: whereas Zuckerman uses a further 

 subadult stage ("third molar unerupted"), Ashton and Spence have no 

 further subadult stage; their ensuing stage is defined as "Adults with all 

 permanent teeth fully erupted." Thus, while the specimens in their inter- 

 mediate category, "stage c," may have included some representing indi- 

 viduals younger than the type specimen of H. habilis, the category may 

 likewise have included some older ones, sufficiently older to have reached 

 the probable value of 100 per cent of adult cranial capacity. For immature 

 specimens, Ashton and Spence did not separate capacities for males and 

 females but rather lumped them into a single combined-sex category and 

 compared their mean with that of a combined-sex sample of adults. 



The figures cited by Ashton and Spence for 4 living hominoids are 

 as follows (I have included in parentheses 2 amendments based on my 

 own computations from the actual means given by these workers): * 



•Table after Ashton and Spence 1958, p. 171. 



69 l< 



