Humans evolved to be omnivores. We'll eat anything we can get our hands on - fruit, vegetables, beans, grains, meat - and we've invented innumerable ways to cultivate and refine those basic ingredients, particularly in the last 10,000 years or so since the agricultural revolution.





But diet in the past was limited, primarily by geography but also by social class or culture. Before the New World was discovered, Italian food had no tomatoes. Before the industrialization of food production, many items we think of as dirt cheap today, like salt, were too expensive for the poor to purchase. If you didn't live on the coast, you probably weren't eating seafood.





When we talk about ancient diets, then, we're looking primarily at commonalities - what the average person was eating - while at the same time understanding that omnivores make for a dietarily heterogeneous population. There is no singular "American" diet, but we can agree that most of us likely consume a large amount of corn-based products, which are cheap and ubiquitous in the form of corn syrup, tortilla chips, popcorn, etc. This reliance on corn, a crop native to the New World , means that the average American diet differs from the average European, African, or Asian diet. Biochemically, we can see this difference in carbon isotopes, and we can show that their value increased following the transition to maize agriculture in the Americas (see, for example, Tykot 2006 ). My carbon isotope value is almost certainly higher than that of most contemporary Europeans.





Roman-era Mosaic

Similarly, there is no singular "Roman" diet, particularly in the Empire when goods were moving around at astounding rates, although researchers agree that a heck of a lot of wheat was consumed by all social classes and that olives and olive oil contributed a number of calories and fat to most people's diets. Ancient historical sources also seem to agree that no one really liked barley and that millet was only consumed in times of struggle, as both of these grains make inferior bread compared to wheat (Garnsey 1988). Yet dried millet tended to keep longer than other grains, making it good for storage along with dry legumes like chickpeas, lupin beans , and lentils, the latter another food that was most often consumed in times of shortage.





Ordinary Romans - that is, small farmers, peasants, and rural slaves who made up the majority of the ancient Italian population - likely got a large chunk of their diet from their non-cash crops like millet, legumes, and turnips, at least based on what writers such as Columella, Strabo, and Galen tell us (Garnsey 1988). Their daily diet would have been a far cry from the exotic foodstuffs found at elite banquets. But, as Horace writes, "Ieiunus raro stomachus volgaria temnit" (Satires II, 2, xxxviii). A hungry stomach rarely scorns plain food.





In order to find out what kinds of plain food the ancient Italians were eating, bioarchaeologists are starting to perform carbon and nitrogen isotope analyses of skeletons (e.g., Prowse et al. 2004, Prowse et al. 2005, Craig et al. 2009, Rutgers et al. 2009, Killgrove 2010). Biochemical analysis isn't perfect, as it only yields a very macro-view of the diet. That is, the carbon isotope ratio can provide information about the kinds of plants and grains consumed, and the nitrogen isotope ratio can provide information on the relative amount of legumes and fish consumed. But depending on the rate of bone turnover, which can be different in different people because of age or disease status, the C and N isotopes represent an average of the last perhaps 5-10 years of a person's diet. With that in mind, here's what the skeletons are telling us about what people were eating in the Roman suburbs and down along the coast during the Empire:





(Click to embiggen)

The carbon axis shows that the people living in the Roman suburbs and along the coast were eating mostly wheat and barley (C3 foods, which have lower carbon isotope values) rather than millet (C4 food, which has a much higher carbon isotope value, starting around -13.0 permil). But their carbon values are higher than a purely C3-based diet, so those could be affected by marine resources and/or consumption of animals that were foddered on millet. The nitrogen axis shows that most people were eating a terrestrial, fairly omnivorous diet, with the coastal population of Velia eating a surprisingly little amount of fish. The pure vegetarians would be at the low end of the N axis, and the pure pescatarians would be at the high end (along with breastfeeding infants).





So what is the recipe for a Roman diet? Well, it's a little bit of everything, really. But you wouldn't know that from reading the half dozen or so cookbooks that contemporary authors have written to approximate Roman cuisine. For example, my copy of A Taste of Ancient Rome, while it has much to recommend it, has just two recipes that include lentils and none that include millet.





In his Historia Naturalis, Pliny notes that Campania in particular is full of millet and that peasants often mixed bean-meal (lomentum) with millet flour. Since cooking and chemistry are two sides of the same coin, I decided to remedy this omission by creating an historically-accurate dish that a Roman peasant might have eaten but also one that would show up isotopically in the skeleton (if eaten in large enough quantities).