AUSTRALOPITHECINES — ROBINSON 495 



On this view it is clear that Paranthropus belonged to a relatively 

 slow-rate line which did not alter in essentials after it had come into 

 existence and was still extant after Australopithecus had become 

 extmct. Progressive desiccation forced some early australopithecines 

 to become meat eaters to some extent; not pure carnivores, but 

 omnivores depending on both vegetable food and meat. The altered 

 selection pressures directly due to this resulted eventually in in- 

 creased brain size and toolmaking and thus in the emergence of man. 



ECOLOGICAL COMPETITION 



From the fact that Paranthropus appears to be well adapted to a 

 vegetarian diet and is found in periods which are at least moderately 

 moist, it seems that its ecological requirements differed significantly 

 from those of Australopithecus. The latter appears to have been a 

 typically hominid omnivore and is usually found under climatic con- 

 ditions noticeably drier than those for Paranthropus. It is probably 

 not valid to conclude that Australopithecus lived only under condi- 

 tions of appreciable aridity; its food requirements were apparently 

 such that there is no reason to suppose that wetter conditions would 

 adversely affect its way of life. However, Paranthropus., being a 

 vegetarian but not a grazer, would find the sort of semiarid conditions 

 easily endured by Australopithecus unsuited to its way of life. It is 

 quite probable that neither would have found wet, dense forest con- 

 ditions congenial. 



Wliat deductions can be made about the ecology of these two forms 

 are in agreement with, and closely related to, the morphological evi- 

 dence which indicates that Paranthropus is an aberrant hominid, 

 while Australopithecus fits very well as an early hominid with char- 

 acteristics which are basically just like those of the more advanced 

 hominids but less well developed. "Telanthropus" would appear to 

 be one of these more advanced hominids with characters basically like 

 those of Australopithecus but more advanced. "Telanthropus," as I 

 have attempted to show, appears to have been a toolmaker and pre- 

 sumably had a larger brain than Australopithecus. The ecological 

 requirements of these two forms are therefore likely to have been very 

 similar, and if they simultaneously came to occupy the same territory 

 they would fijid themselves in competition unless there was an over- 

 abundance of their necessities for life. But since the ecological re- 

 quirements of Paranthropus were different, it could coexist quite well 

 with either of the other forms. 



The evidence from the Sterkfontein Valley seems to support these 

 conclusions. Au^stralopithecus lived in the valley for quite a long 

 period of time when conditions were relatively dry. If my inter- 



