climate, disease, and the end of an empire

​For there is no truly comparable phenomenon except the Chinese Empire, which appeared at the same time, but never – permanently – fell. China had an emperor until 1911, and still exists today as a unified state under a single government, ruling a single people created by that ancient state. History tells us about Rome’s politics and ideas in great detail, and something of what lies beneath the surface: archaeology, economics, sociology, technology, and the natural world during these times, albeit that much of the latter has been little known until the present. But in his Fate of Rome Harper fluently synthesizes knowledge of climate history, infectious disease, ancient literatures, and the Roman economy to give us a thorough “physical” of the Roman Empire, identifying underlying conditions that led to its long health, prosperity, and population growth, but sowed the seeds of its eventual breakdown. The first of these is the “Roman Climatic Optimum”, or “Roman Warm Period” from about 250 B.C. to about A.D. 400, during which higher average temperatures and increased rainfall permitted a very large extension of cultivated land and agricultural productivity throughout the Mediterranean world. The increased food supply led in turn to unprecedented growth in population, social complexity, commerce, and urbanization. Large and numerous cities were connected and supported by trade carried on by a uniquely mobile population using roads, rivers, and sea lanes. Rome was the world’s first city to reach a million people, and required the Egyptian wheat crop for its daily sustenance, brought to it by a government-subsidized system of shipping and distribution.
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Yet this huge and interconnected population also fostered the evolution of epidemic disease in unprecedented ways. Disease and mortality constituted a huge part of daily life at this time, largely from malaria and intestinal infections, but the high normal death rate did not impact political events or population size. However three terrible pandemics of a severity then unknown in human civilization swept and devastated, even perhaps halved the Roman population. Previous epidemics were commonplace but limited; these new highly contagious diseases for which people had no immunity, possibly leaping for the first time from some animal reservoir, spread like wildfire throughout the empire, killing vast numbers on a daily basis. Each of these – the Antonine Plague, Plague of Cyprian, and Plague of Justinian – led a highly intelligent and articulate observer to describe its symptoms and effects.

Here.