¢ 1 cosa non mi riCordo menTioned in The History of the Decline and Fall of the Roman Empire ... is the importance of agriculture & rural:urban ratio: «During the Roman Empire, there were approximately 9 people living a rural life to every 1 person living an urban life. Today, that ratio is closer to 1:1 (in the USA, it’s 1:3). Ancient populations could not allow for such a ratio simply because of the low marginal return of human/animal based agriculture. All of the ancient world’s social complexity- the religious institutions, the armies, the governments, the urban and nonproductive citizenry- were supported on the relatively low marginal yields of annual human/animal agriculture. This had a number of consequences, most notably that ancient society was susceptible to the effects of variants in agricultural output (weather, pestilence, soil salinization, marauders, etc). Ancient society could only exist within the limits of the marginal yield of its agriculture, but when circumstances led to a collapse of that marginal yield, so too did that society collapse. Inversely, ancient society could only solve problems within the capability that the marginal return of human/animal agriculture allowed.» 3.
Which is fine, true and dandy, as far as it goes. But that isn’t far enough. There’s yet another factor in the equation. The work to turn wheat (or any cereal) into an easily assimilable form of energy to drive all that social complexity. For which, I would refer him to Rachel Laudan’s tour de force Fueling Mexico City, which includes a Roman context.
If you’ve got a city of a million, like ancient Rome, you’ve got to get two million pounds of grain into the city every day. It’s the same for all the cities in the world -— it’s 2 lbs of grain per person. That’s the power, that’s the energy that drives cities.
Merely bringing the grain into the city is barely the half of it. It needs to have been threshed, much more difficult for the hulled wheats that dominated cereal culture then. And milled at least partially. And cooked into gruel or, if the circus was in town, bread. Where are all the labourers who perform those tasks in Mr Gibbon’s calculations? I reckon feeding Rome was even harder than most people imagine.