One of the most difficult parts so far of researching traditional barbacoa has been trying to nail down its history, both recent and pre-Conquest. There are plenty of myths out there — the things people say and repeat, often without any evidence other than that someone else said it. But I’ve been surprised at how thin the historical record is and even more surprised how thin the anthropological/archaeological record is. Even in books devoted to the history of food in mesoamerica, earth oven cookery is rarely mentioned.
However, I was happy to find, recently, the work of Professor Stephen L Black, especially his article co-authored with Alston V Thoms entitled, “Hunter-Gatherer Earth Ovens in the Archaeological Record: Fundamental Concepts.” Here is the abstract:
Remains of earth ovens with rock heating elements of various sizes and configurations are common at hunter-gatherer sites around the world. They span the last 30,000 years in the Old World and some 10,000 years in the New World. Although various foods were baked in these ovens, plants predominate. Earth ovens are ethnographically well documented as family-size and bulk cooking facilities, but related technology and its archaeological signatures remain poorly understood and understudied. These ubiquitous features are often mischaracterized as generic cooking facilities termed hearths. It is proposed that, in fact, most rock “hearths” are heating elements of earth ovens. Reliable identification and interpretation of earth ovens requires documentation of heating elements, pit structure, rock linings, and various remnants thereof. Fundamental technological concepts for investigating their archaeological signatures include thermodynamics, construction designs, and life cycles in systemic context, as informed by ethnographic, archaeological, and experimental data. Earth oven technology explains well the primary purpose of labor-intensive thermal storage for long-term cooking and conserving fuel. Information from the extensive archaeological record of earth ovens on the Edwards Plateau of south-central North America illustrates these points.
It’s really a primer on the archaeology of earth ovens. The bibliography will be an opportune rabbit hole that I look forward to getting lost in, but the article itself has a lot to offer, including the basic timeline of earth oven usage and its spread across the globe, how to spot the remains of earth ovens, the science behind the effectiveness of earth ovens, the nutritional advantage of earth ovens, and the basic technology of how earth ovens work.
Take, for example, this outline of the basic structure of earth ovens, as illustrated by the picture at the top of this page:
In its moist-heat baking mode, a typical earth oven consists of seven layers (Figure 1), from bottom to top: (1) prepared surface (i.e., basin or deeper pit); (2) fire (reduced to glowing coals and ashes when oven is sealed); (3) layer of hot rocks; (4) lower layer of green plant material, which we call packing; (5) food being baked; (6) upper packing layer; and (7) earthen cap. The packing layers envelop the food, keeping it clean, supplying critical moisture, and adding flavor. Moist heat allows the food to undergo hydrolysis, during which complex molecules are broken into smaller, more easily digestible molecules (Wandsnider 1997). A moist-heat baking environment is also essential because, as long as adequate moisture from the packing material and food is retained in the oven (water is sometimes added), the temperature of the food remains below the phase change from water/liquid to steam/gas (ca. 100°C) and thus prevents burning/charring the food (Stark 1997).
This gives basic insights into the process for making barbacoa and what is necessary to the process and how it has changed or stayed the same throughout its history. I can’t help but notice, for example, that while we think of this earth oven technology as primarily a means to cook meat, the earth ovens were originally used more for vegetables, especially those least digestible. I have always thought of mezcal production as a post-Conquest technology. However, the cooking of the agave roots in large underground pits, while it may today be used almost exclusively as the first step towards turning starch to sugar to alcohol, it is clearly a process that pre-dated the Spanish, but turned the starch to sugar to food.
If you want to check out some of the field work Black and his students are doing on earth ovens, you can check out this blog post on earth ovens in Nevada, too.