Provisioning Rome, one of the world’s largest cities, if not the largest with as many as a million people by about 55 B.C., was one of the greatest challenges of the Ancient World.
Bread was the basis of the diet, supplying most of the calories for most of the population. So getting grains, particularly wheat, into Rome was the major provisioning problem.
The map above shows what it cost to get grains to Rome from different parts of the Mediterranean. It’s by classicists Walter Scheidel and Elijah Meeks at Stanford, and is on their wonderful site, Orbis: The Stanford Geospatial Network Map of the Roman World. They say:
Conventional maps that represent this world as it appears from space signally fail to capture the severe environmental constraints that governed the flows of people, goods and information. Cost, rather than distance, is the principal determinant of connectivity.
Or in other words, miles are less important that what the cost of traveling those miles.
For most of history, travel by water where the current or the wind supplied the power was much, much cheaper than travel by land where animals (human porters, mules, oxen) provided the power. Those animals had to be fed. Even if there was a lot of grass or other food along the way, they needed grains for energy. As quartermasters from Alexander’s time to World War I knew, animals quickly went through the grains they were transporting.
The Orbis map above shows that it made sense to import wheat from Egypt, the Black Sea, or North Africa at a price of between 2.5 and 4.5 denarii a kilo rather than bringing it by sea than from overland the much shorter distance from the inland northern Mediterranean where transport costs quickly went above 4.5 denarii a kilo.
And if you wonder about all these strange measures, a kilo of grain is 2.2 lbs. It will make a little over three 1 lb loaves of white bread or four 1 lb loaves of wholewheat bread. (A small American wrapped loaf weighs 1lb).
All except the rich (who got many of their calories from oil or wine or perhaps meat or cheese) would have needed at least a pound of bread a day. For those engaged in heavy labor it was more like 2 lbs.
A pound loaf of bread cost about 2 denarii (a pair of army boots was 22 denarii, a farm laborer might get 2 denarii a day plus what he received in kind, mainly food).
Let’s assume the pound loaf was wholewheat. Then the cost of shipping the wheat for four loaves (8 denarii) from Egypt or north Africa was at least 2.5 denarii. Or in other words about 30% of the cost of a loaf of bread was for the shipping.
This is a minimum. If the loaf were white, if the cost of shipping was more than 2.5 denarii, then the percentage going to shipping went up sharply.
This does not count the cost of growing the wheat, or of grinding, sieving, kneading, shaping, and baking the loaves.
Remember, these are all order of magnitude estimates, which would have varied with weather, time period, etc.
But two things stand out. The miles wheat was transported mattered much less than whether that transport was by land or sea. And supplying a city such as Rome was costly, difficult, and did not allow much room for error (missed shipments).
And do take a look at the Orbis site. Quite fascinating in itself and as an example of what computers can do for the historian. I wish I had had it when I was writing Cuisine and Empire.