continual vigilance against a wide variety of predatory threats, day 

 and night. In my opinion, such threats must have represented a sig- 

 nificant selective pressure in favor of any advance in intelligence 

 and resulting technology that could have reduced the threat. But it 

 is not only among hominids that predation appears to have driven 

 the course of animal evolution. How long has the process of pre- 

 dation been a factor in the evolution of animal life? To answer that, 

 let us go back in time to the very beginnings of animal life. 



The Ancient Roots of Predation 



The evidence at Swartkrans convinced me of the importance of 

 predation to the evolution of intelligence and I was keen to know 

 more of the ancient roots of predation among the earliest animals. 

 It is well-known that remains of animals date back to Terminal Pro- 

 terozoic times, almost 600 million years ago, and some of the best 

 evidence in this regard can be found in sediments belonging to the 

 Nama Group in Namibia that were accumulating in a shallow sea 

 on the western edge of the Kalahari Craton at the time of the as- 

 sembly of Gondwanaland (Brain, 1997b). It is to the fossil record 

 from the Nama Group, as well as from the somewhat older Otavi 

 Group on the Congo Craton further to the north, that I have given 

 my attention in the last few years. 



Late Proterozoic times, when animals first left abundant traces in 

 the fossil record, were preceded by several very severe glacial pe- 

 riods. Glacial deposits from two of these episodes, each with their 

 very distinctive "cap-carbonates," have been recognized in northern 

 Namibia (Hoffmann and Prave, 1996), as well as elsewhere in the 

 world. Based on these, Paul Hoffman and his colleagues (1998) have 

 invoked the "snowball earth" scenario, first proposed for earlier 

 Precambrian low-temperature episodes by Kirchvink (1992). The 

 concept addresses the problem of low-latitude glaciations, as are 

 indicated by the Namibian evidence, and proposes that the oceans 

 froze over and that biological productivity collapsed for some mil- 

 lions of years. It was only through the abundant production of car- 

 bon dioxide by active volcanoes that a "greenhouse" situation de- 

 veloped, rapidly melting the global ice and swinging the climate to 



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