Table 3: Cranial capacity estimates of available sample of Australopithecus sensu lato " 



Specimen Capacity (in ex.) Specimen Capacity (in c.c.) 



Taung (adult value) 540(440) Sterkfontein 71 480-520(428) 



Sterkfontein 60 435 (428) Sts 19/58 530 (430) 



Sterkfontein 5 480 (485) MLD 37/38 480 (435) 



Mean for 6 South African gracile australopithecine 



specimens (A. africanus) 494 (442) 



Swartkrans (SK 1585) Olduvai (Old. 



(A. robustus) 500 (530) Horn. 5) 



(A. boisei) 530 (530) 



Australopithecinae (adult sample range) (n = 8) 435-540 (428-530) 



" The values in parentheses are those of Holloway ( 1970b). 



Estimate of population range for A. africa?ius 



Table 3 summarizes all the data for the presently available sample of 

 australopithecines (n = 8). From the A. africanus sample, an attempt may 

 be made to arrive at population limits for the taxon. First, it is necessary to 

 compute a standard deviation of the mean (S.D.) from this small sample. 

 Rather than estimate this from the actual deviations from the sample 

 mean, an estimate of the standard deviation for the population has been 

 derived from the sample range, following Simpson, Roe, and Lewontin 

 (i960, p. 141, Table 1a) and Lindley and Miller (1953, p- 7, Table 6). The 

 S.D. on this basis is 41.5 c.c. (My former estimate of 47 c.c— Tobias 1968b 

 —was based upon a sample of 7 australopithecine estimates, including 

 A. boisei of Olduvai; furthermore, as the "adult value" for Taung, I then 

 used the figure of 562 c.c.) For comparison, Robinson's latest proposed 

 S.D. for 6 A. africanus values is 50 c.c. (derived from the range quoted by 

 him— 1966, p. 958), whereas that of Holloway (1970) is only 21.59 c.c. 



An estimate of the gracile australopithecine population range based on 

 the formula, sample mean ±3 S.D., gives values of 370 to 618 c.c. when the 

 sample mean of 494 c.c. and S.D. of 41.5 c.c. are employed.* (This contrasts 



•Computed from Holloway's provisional mean of 442 c.c. and his standard deviation of 21.59, 

 the estimated population range, based on mean ±3 S.D., is 377 to 507 c.c, that is, a remarkably 

 similar lower limit, but an upper limit well short of the previous estimate. On a mean of 450 c.c. 

 and S.D. of 22.49 c.c. (see footnote on page 21), the limits would be 383 to 517 c.c. However, as 

 Holloway (1970b) has pointed out, 21.59 c.c. is an extremely small S.D. when compared with the 

 variation of extant pongid samples: this smallness is "probably due to both the small sample 

 size of gracile forms, and a bias introduced from using certain gracile forms to estimate the 

 volume of others" (1970b, p. 968, note 8). 



27 u 



