Table 14: Jumps in cranial capacity from Australopithecus to 

 Homo e rectus 



A. afrkanus (if x = 494 ex.) to //. habilis (if x = 656 ex.) 162 ex. 



A. afrkanus (if x = 494 ex.) to H. habilis (it v = 668 c.e.) 1 74 i x. 



A. afrkanus (if x= 442 ex.) to H. habilis (if v = 656 ex.) 214 ex. 



A. afrkanus (if x = 442 ex.) to H. habilis (if v = 668 ex.) 226 ex. 



H. habilis (if v = 656 ex.) to H. erectus erectus (x = 859 ex.) 203 ex. 



//. habilis (if x = 668 ex.) to H. erectus erectus (x = 859 ex.) 1 9 1 ex. 



//. erectus erectus (x = 859 ex.) to H. erectus pekinensis (x = 1043 ex.) 184 ex. 



Table 14 shows the intervals in the series of group means. It is interest- 

 ing to note that the jump from the small sample of H. habilis (n = 2 or 

 3) to that of H. erectus erectus (?i = 6, excluding Lantian) is only slightly 

 more than that from the Indonesian to the Choukoutien groups of 

 H. erectus. Yet the latter 2 groups are recognized as belonging to the 

 same species! In other words, the difference in mean cranial capacity 

 between 2 subspecies within H. erectus is only slightly smaller than that 

 between the smaller-brained of the 2 subspecies and the habilis group, 

 which some regard as a different genus (Australopithecus), from H. erectus. 

 This underlines my contention that the rate of increase of brain size itself 

 accelerated with the emergence and subsequent evolution of Homo erectus. 

 Figure 31 attempts to depict this rising tempo of encephalic incre- 

 ment from taxon to taxon.* It is of interest that the sequence corre- 

 sponds roughly to the passage of time. Thus, while A. africanus and 

 H. habilis overlap in time, it seems that the latest H. habilis populations 

 outlasted the latest A. africanus. The evidence from Olduvai and from 

 the Transvaal sites suggests that A. africanus was essentially a Lower 

 Pleistocene (and probably, too, an Upper Pliocene) phase of hominid life; 

 H. habilis was a Lower Pleistocene phase which apparently lasted into 

 the earliest part of the Middle Pleistocene (as represented by Olduvai 

 Bed II just above the faunal break). H. erectus erectus seems to have 

 lived from the earliest to early Middle Pleistocene; H. erectus pekinensis 

 perhaps in the middle part of the Middle Pleistocene; and H. sapiens 

 from later Middle Pleistocene to Upper Pleistocene. These times are 

 only approximate, for there is no clear and universally applicable defini- 

 tion of the boundaries between the different stages of the Pleistocene, 



•Figure 31 does not take Holloway's (1970b) new estimates for Australopithecus nor Sartorto's 

 new H. erectus VIII into account. 



97 & 



