In this grim, imagined scene of a post-nuclear-war world that has been bombed back to the Stone Age, Herblock injects humor by caricaturing survivors as cavemen. Discovery of a past agreement curtailing the spread of nuclear arms provides a sober warning that even treaties cannot prevent nuclear annihilation. In 1963 the U.S., Soviet Union, and United Kingdom agreed to ban all but underground nuclear tests, yet by 1964, France and China had developed nuclear capability.