From the point of view of processes, the evolution of Homo sapiens 

 is unique. The evokitionary forces described thus far have played 

 and still play an extremely important part in human evolution. 

 However, in addition to these forces, an entirely new kind of evolu- 

 tion, that of culture, has entered the picture. This nongenetic body 

 of information is, like genetic information, transmitted from genera- 

 tion to generation. The evolution of all organisms except man de- 

 pends, with very minor exceptions, upon the information stored in 

 the nucleotide code and upon its expansion and rearrangement 

 through mutation and recombination. In man there is superim- 

 posed upon this a large body of extrinsic information which, at least 

 in theory, is potentially available to all members of the species. 

 Through the utilization and manipulation of this body of informa- 

 tion, man has evolved prosthetic devices ( both mental and physical ) 

 that have given him a unique ability to modify his environment and, 

 indeed, to influence the evolution of all organisms on the face of the 

 earth. 



MAN'S EVOLUTIONARY HISTORY 



Man shares a vast inheritance with all mammals. Those interested 

 in the long story of the attainment of mammalhood are urged to 

 consult textbooks on vertebrate paleontology. The conquest of land 

 by vertebrates and the eventual appearance during the age of the 

 dinosaur of our inconspicuous warm-blooded ancestors with differ- 

 entiated teeth and highly developed devices for fetal nourishment 

 make a fascinating story. However, it is a story which sheds little 

 additional light on the processes of evolution. The genotypes that, 

 through recombination, provided more efficient tetrapodal locomo- 

 tion, eggs resistant to desiccation, metabolic control of body tem- 

 perature, faster conducting neurons, and all the other "inventions" 

 on the road to the status of mammal contributed their information 

 differentially to the gene pool of subsequent generations. At some 

 point early in mammalian history, quite likely in the Paleocene (70 

 million years ago ) , came the first evolutionary step that was to lead 

 eventually to the differentiation of man from the rest of the mam- 

 mals through the possession of culture. 



We can only guess at the reason or reasons for this step; perhaps 

 it was the presence of efficient terrestrial predators, perhaps an 

 abundance of fruit. But, for whatever reason, in one group of mam- 

 mals, individuals living in the branches of trees and shrubs started | 281 



