Keys' thesis in Catastrophe is that a global climatic catastrophe in A.D. 535 to 536 —— a massive volcanic eruption sundering Java from Sumatra —— was the decisive factor that transformed the Ancient World into the Medieval Era (and beyond). Ancient chroniclers recorded a disaster in that year that blotted out the Sun for months (possibly years) causing famine, droughts, floods, storms and an epidemic of bubonic plague. Keys uses tree-ring samples, analysis of lake deposits and ice cores, as well as contemporaneous documents to bolster his speculative thesis. In his scenario, the ensuing disasters precipitated the disintegration of the Byzantine Empire, beset by Avar, Slav, Mongol, and Persian invaders propelled from their disrupted homelands. The Sixth Century collapse of Arabian civilization under pressure from floods and crop failure created a religiously apocalyptic atmosphere which set the stage for the emergence of ’Isl?m. In Mexico, the cataclysm supposedly triggered the collapse of Teotihuacán; while in China, the ensuing half-century of political and social chaos led to a reunified nation. Keys stokes anxieties about future cataclysms by finishing with a roundup of trouble spots that could conceivably wreak planetary havoc.

Critique

Critics have accused Keys of oversimplifying history with a "single chain of causality". He has been charged with reassembling history to fit his thesis, "relentlessly overworking its explanatory power in a manner reminiscent of Velikovsky's theory that a comet collided with the earth in 1500 BC" (Publishers Weekly). Nevertheless, Keys worked his treatise with the advice of dozens of academic consultants. Writing in The New York Times Book Review, Malcolm W. Browne insists that "...this book must be taken seriously, if only as a reminder that survival in a world threatened by real dangers hangs by a very slender thread."