they have already opted for a division of labor 
that affects the whole society. They have become 
settled and have begun to specialize. Writing is 
impossible for man the food gatherer but it is 
inevitable for Neolithic man, the agriculturist.

Marshall McLuhan, “The Role of New Media in 
Social Change,” Marshall McLuhan: The Man and  
His Message , (Golden, 1989) p. 35.