L3 POSTLUDE 



A 



J^f This book has been more in the nature of an essay than a scientific 

 treatise: for an essay sets out to explore ideas but does not necessarily prove 

 anything! If one thing has been proven here, it is our need for much further 

 information on many basic facts. 



We have explored such facts as do exist on endocast size and have tried 

 to add to the existing corpus of knowledge. We have made a few rudi- 

 mentary attempts at computing population limits for various taxa of fossil 

 hominids. We have shown that the greatest advance in mean cranial ca- 

 pacity apparently occurred between the Lower and Middle Pleistocene, 

 with the emergence of Homo erectus. 



On the other side of the coin, we have surveyed the evidence on cul- 

 tural origins and early cultural growth. Here, too, we have seen that the 

 most significant of the early cultural advances came with the rise and de- 

 velopment of Homo erectus. 



We were struck by the fact that of all the elements of hominization, 2 

 were alike in being long continued, sustained, and most marked: brain-size 

 increase and cultural evolution. No other parameter for which adequate 

 evidence is available equals these 2 in duration and continuity. We were 

 constrained to probe below the surface, to seek the causal links between 

 both ends of the chain leading from increased brain size to increased cul- 

 tural complexity. 



We considered the structural meaning of variations in brain size, both 

 absolutely and in relation to body size. We spoke of neuron numbers and of 

 internal reorganization of an enlarging brain, and examined the interrela- 

 tions of the various parameters. We realized that the area between the hard 

 factual extremes (endocasts and implements) was a shadowy, twilight zone 

 of controlled speculation. We saw that a few venturesome souls are trying 

 to throw light on this gloomy zone and thereby to rationalize the causal steps 

 between brain size and tools. While pausing to doff our caps at them, we 

 concluded that both termini of our causal chain were worthy objects of 

 study in their own right, as long as we observe due restraint in the func- 

 tional and behavioral interpretations we make from them. 



151 ^ 



