'Hope springs eternal' is the last sentence of this lengthy speculative article. It may as well have been the title since all the author's conjectures on the evolution of man lead to one final question: Should we be as gloomy about the future of civilization as Freud with his emphasis on repression as the basis of civilization or as optimistic as Norman O. Brown with his emphasis on Eros? Endleman's contribution to a theory of human evolution is in his discussion of the dialectic relationship between play and language with a description of seven different prelinguistic vocalizations.