climatically mediated that I started reviewing evidence for the Ce- 

 nozoic cooling mentioned earlier. 



The erosion of perhaps 50 metres of dolomitic hillside above the 

 cave, together with the upper part of the cave-filling itself, has 

 doubtless removed a good deal of the evidence for stratigraphic 

 complexity at Swartkrans. But what is left, and came to light during 

 our excavation, indicated five depositional members, each separated 

 from adjacent neighbors by erosional discontinuities. The earliest of 

 these is designated Member 1 Lower Bank, followed by Member 1 

 Hanging Remnant, Member 2, and Member 3. All of these have 

 remains of robust australopithecines in them and are thought to vary 

 in age from 1.8 to 1 million years. Member 4 is a Middle Stone 

 Age deposit with abundant stone artifacts, but little bone, while 

 Member 5 appears to be about 1 1 ,000 years old, with a fossil as- 

 semblage suggestive of the food remains of leopards. 



Although the fossil sample from the Hanging Remnant that re- 

 sulted from the early excavation of Broom and Robinson has many 

 superb hominid fossils in it, its use is limited from the perspective 

 of taphonomic interpretation. The extremely hard matrix was first 

 dislodged with dynamite and the resulting blocks were then broken 

 up with hammers. When an interesting-looking fossil was broken 

 through, particularly if it was a cranial piece, it would be kept for 

 subsequent preparation, but many other bones were simply discarded 

 onto the dump. Although we systematically searched through the 

 excavation dumps, recovering some specimens, many others had 

 been carried away in the intervening years by casual visitors to the 

 site. The final Hanging Remnant sample was therefore biased in 

 favor of cranial pieces and, very probably, in favor of primates at 

 the expense of less spectacular mammals. Described in detail else- 

 where (Brain, 1981a), the assemblage was found to consist of 2,381 

 bones from 41 identified taxa, shown diagrammatically in figure 2. 

 Primates — baboons and hominids — made up 47% of the total num- 

 ber of individuals — followed in abundance by ungulates (35%) and 

 carnivores (12%). 



By contrast, our excavation in the Lower Bank of Member 1 

 yielded a total of 153,784 pieces of fossil bone that were analyzed 

 in detail by Virginia Watson (1993). Of the animals that had con- 



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