The author is indebted to the following for their advice and suggestions: Mark Hall of Berkeley for his modern views of ancient man; Dr. John O'Brien for information on broken arms and emergency room traumas; Professor Sidney Coleman of Harvard for the vagaries of time relative to interstellar speeds; Maude Kirk for reading portions of the initial draft and offering valuable insights; Robert Austin of Synetic Systems of Seattle for input on "artificial realities" and future computers; Jeff Windle, who cheerfully shared his enthusiasm for rock climbing; Charles N. Brown, who had helpful views on subtext in novels; and Chuck Fruchey, Bob Stephens, Sherry Gottlieb, David Moloney and Richard A. Lupoff, all of whom gave valuable suggestions.