Climate and Disease in Medieval Eurasia
This is an advance summary of a forthcoming article in the Oxford Research Encyclopedia of Asian History. Please check back later for the full article.
From the time the first hominids migrated north from Africa, shared exposure to infectious disease across the wide geographic and climatic expanse of Eurasia has likely been common. Vivax malaria, for example, was probably brought to Asia during the first in-migrations of Homo sapiens. But whereas vast distances and low population density likely shielded Eurasian populations from frequent epidemic outbreaks up through the Neolithic period, by the beginning of the modern era Eurasia would begin to see a new phenomenon: pandemics. The Bronze Age likely saw the evolutionary origin of what would become the world’s leading infectious killers—tuberculosis, plague, and smallpox—and then the emergence of modern forms of severely disabling disease, such as leprosy. The medieval period created increasing linkages in that microbial web, and by ca. 1500, Eurasia (and much of Africa) would now be united in an interconnected disease environment. Throughout this period, climate played a role in human health, not simply in the obvious ways of determining the success of year-to-year harvests, but in more fundamental ways, as periods of warming or severe and sudden cooling shifted the interactions between humans and all the flora and fauna that made up their environment.