494 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1961 



populations will probably have died out entirely, but it is not un- 

 reasonable, in view of known evidence of primate dietary adaptability, 

 to suppose that some groups will have succeeded in surviving on their 

 modified diet. 



However, these changed conditions will also have modified the 

 selection pressures operating on the population. It would seem ob- 

 vious that intelligence would be at a premium since some ingenuity 

 would be required to get enough to eat, whereas this is much less so in 

 the case of a vegetarian living under reasonably wet conditions. The 

 more intelligent ones would therefore be able to adapt better to the 

 changing conditions and are likely to have been the parents of the 

 majority of the next generation. Also, whereas the simplest tools 

 suffice for a vegetarian and in almost all cases none at all are needed, 

 tools would obviously be of great use to the population adapting to 

 more arid conditions. Implements for digging animals out of holes, 

 snares for catching prey, implements for bashing or opening up 

 animals, would all enable far more efficient adaptation. 



The onset of drier conditions would therefore seem to lead in- 

 evitably to strong selection pressure in favor of tool using and im- 

 proved intelligence in an early australopithecine population remain- 

 ing in the areas affected. Other adaptive features might also be the 

 retention of relatively large (for hominids) canines, or the increase 

 in their size. Also smaller body size will have had adaptive value if 

 the ancestral Paranthropus was as large and robust as the known 

 ones. Where food scarcity combines with the need to be agile to get 

 enough to eat, litheness and moderate size are advantageous. This is 

 especially true when the adaptive process has reached a point where 

 meat eating involves killing antelope and other mammals larger than 

 the small creatures eaten in the earlier stages of adaptation. 



In this manner it is easy to explain the origin of Australopithecus. 

 But once this process had reached the point of producing such a 

 creature, there is no reason at all why it should stop there. Improved 

 intelligence and improved facility with tools would continue to im- 

 prove adaptation and it would appear that sooner or later — and 

 probably relatively soon — a stage would be reached when conceptual 

 tjiouglit would begin to appear and tool using would improve to tool 

 making as well. This point, of which tool making is, as it were, a 

 symptom, seems a logical place to regard as that at which true man 

 emerged. It was here that the fundamental feature of man, culture, 

 became established. The tool-using phase was essential to its full 

 establishment, but that was a transitional phase. Naturally there is 

 no sharp division between the one and the other, but from our present 

 position in time the point of separation between australopithecine and 

 man is sufficiently defined to be useful. 



