Just as the progress of a disease shows a doctor the secret life of a body, so to the historian the progress of a great calamity yields valuable information about the nature of the society so stricken.
Men make their own history, but they do not make it as they please; they do not make it under self-selected circumstances.
In the past twenty years, historians, archaeologists, and scientists have become increasingly aware of the extent to which the first half of the sixth century would appear to have witnessed a period of major climatic instability which would serve to transform the conditions in which societies across the northern hemisphere operated. The effects of such climate change in the 530s would soon be compounded by a (probably connected) series of outbreaks of epidemic disease, which would recur until the middle decades of the eighth century. Across much of Eurasia in particular, therefore, but also including Arabia and parts of Africa, the Early Middle Ages would be characterized by a specific set of climatic and epidemiological circumstances. The impact of both climate change and disease would be most dramatically felt by the first generations to encounter them: it is therefore the voices of authors from the sixth and seventh centuries that will predominate in what follows. Thereafter, societies increasingly developed coping mechanisms (both organizational and psychological), and men and women bedded down into a dogged routine of survival, which has left less of a trace in the written sources on which we primarily rely. Only in the second half of the eighth century would the general dissipation of the late antique waves of epidemic disease finally facilitate an era of renewed efflorescence and growth.
The City of the Three Pyramids
At the start of the sixth century, the city of Teotihuacan, the spectacular ruins of which still stand in the Valley of Mexico some 40 kilometres to the northeast of Mexico City, was perhaps the greatest urban conurbation in the western hemisphere.