492 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1961 



group consisted essentially of tool users. Even the Olduvai evidence, 

 which at first appeared to support the idea that australopithecines 

 made stone tools, is now beginning to appear to oppose such a 

 conclusion. 



ORIGIN OF THE AUSTRALOPITHECINES 



The available australopithecine material makes it clear that erect 

 bipedal posture developed before the brain enlarged beyond the size 

 found in the larger pongids. Some of the more obvious differences 

 between pongid and australopithecine skulls are closely related to 

 erect posture. For example, the altered orientation, reduced size 

 and separation of the occiput into a portion above and one below the 

 inion, are apparently directly due to the acquisition of erect posture. 

 These occipital changes result in the isolation of the sagittal crest 

 from the superior nuchal line and the absence of a true nuchal crest on 

 that line, in a form like Paranthropus^ where muscular development 

 is relatively great for the size of the braincase (Robinson, 1958). 

 Also reduced canine size and the compactness of the anterior teeth 

 and hence the nearly vertical chin region, are doubtless to some 

 extent at least due to erect posture, even if indirectly. One may there- 

 fore conclude that the essential factor in the origin of australopithe- 

 cines was their becoming erect bipeds. This has been discussed else- 

 where (Robinson, 1962), and the conclusion reached that the process 

 occurred in two stages. During the first, pelvic changes were pro- 

 ceeding under the control of selection which was not concerned with 

 erect posture but which resulted in shortening of the innominate bone 

 and broadening of the posterior portion of the iliac blade. This ren- 

 dered the pelvis preadaptive for erect posture and allowed the second 

 phase, adaptive for erect posture, to proceed. Animals with the 

 altered pelvis would find when standing erect, as primates commonly 

 do, that gluteus maosimus no longer functioned as an abductor but as 

 an extensor of the thigh. Thus movement in this position would bo 

 more efficient and would also allow the mobile, grasping hands to be 

 put to much better use than had previously been possible when they 

 were primarily concerned with locomotion. These advantages would 

 result in rapid readaptation of the animals under the quite altered 

 selection pressures now operating and would have opened up quite 

 new evolutionary possibilities. 



Higher primates are vegetarians with very few exceptions. It is 

 highly probable therefore that whatever form was ancestral to the 

 australopithecines will have been vegetarian. Paranthropus was a 

 vegetarian, but Australopithecus was an omnivore. As has been 

 shown, the former is less advanced in the direction of man than the 

 latter and retains more primitive features. It would thus appear 



