The real ecological lesson of the emperor's ceremonial inspection of the grain inventory is hiding just out of sight, in the great storehouses hulking over the landscape. Granaries were everywhere in the later Roman world. The stockpiling of grain was deeply rooted in the Mediterranean psyche. In the empire, the vast network of cities, ships, and stores of grain created an ecosystem. This ecosystem served as an invitation for a species uncannily evolved to be communal - literally to "share a table" - with us: Rattus rattus, the black or ship rat.
- From The Fate of Rome: Climate, Disease, & the End of an Empire by Kyle Harper