Ancient Savannah Roots of the Carbohydrate Revolution in South-Central North America
Thoms, Alston V., Plains Anthropologist
Along the ecotone between North America's southern Plains and southeast Woodlands, the oldest known earth ovens with rock heating elements date to 8,000-9,000 years ago. Through the millennia, the number and diversity of earth ovens increased markedly, but they typically functioned as plant-baking facilities, especially for geophytes, plants with underground storage organs. Among the important early Holocene geophytes in oak savannah regions were onions (Allium spp.) and camas (Camassia spp.). In the drier savannahs, including Texas' Edwards Plateau, agave (Agave lechuguilla) and sotol (Dasylirion spp.), plants with above-ground storage organs, dominated oven cookery. Rock-filled earth ovens were common in comparatively wet regions with sandy soils, including Texas' Post Oak Savannah, but floral preservation conditions are poor. Ethnobotanically and ecologically derived expectations, however, suggest false garlic (Northoscordum bivalve), onions, and spring beauty (Claytonia virginica) as potential plant food staples. Various plant foods were undoubtedly eaten throughout the pre-Columbian era but geophytes appear to have sparked and sustained an ancient carbohydrate revolution that led to significant early Holocene land-use intensification. Such a profound dietary shift may yet be shown to have played an important role in changes in Native American cranial morphology during the early Holocene.
Keywords: southern Plains, geophyte, fire-cracked rock, earth oven, land use intensification
The onset and spread of native agriculture in North America had profound impacts on human lifeways in the southern Plains and adjoining savannah regions (Figure 1), as attested to by papers in this volume. Archaeologists working in savannah regions along the southern Plains-southeast Woodland ecotone have also unearthed considerable evidence for what are arguably pre-agricultural revolutions in subsistence strategies. Among the more notable of these, and the subject of this paper, was the sudden increase in root-food consumption underway throughout the continent by about 9,000 years ago, followed by substantial intensification between 4,000 and 2,000 years ago (Thorns 2003).
This marked change in food procurement strategies is best evidenced by remains of earth ovens, especially those with rock heating elements. The presence and proliferation of fire-cracked rocks (FCR), what I call "cook stone," at archaeological sites have long been recognized as hallmarks of Archaic, as opposed to Paleoindian, lifeways (Willey and Phillips 1958; Wissler 1940). Ethnographic records, in general, illustrate that cook stones functioned in diverse ways (Figure 2), including as heating elements in closed cooking facilities, primarily earth ovens and steaming pits, and in open-air facilities, including those used for stone boiling and griddle cooking (Driver and Massey 1957; Thorns 2003,2007a)
My focus here is on the remains of earth ovens and wild root foods as measures of the "carbohydrate revolution" along the ecotone between North America's southern Plains and southeastern Woodlands. This particular ecotone approximates the boundary separating the Plains, Southeast, and Southwest culture areas (Figure 1 ). I use the term "revolution" to call attention to an unprecedented punctuated onset and subsequent intensification of the exploitation of plant foods. Especially characteristic of the carbohydrate revolution are inulin-rich root foods that require prolonged cooking, usually with the aid of hot-rock heating elements. Inulin, in its raw state, is among the relatively non-digestible (i.e., non-reducing), reserve-carbohydrate forms of fructan. It is rendered significantly more nutritious (i.e., digestible) and sweet tasting when hydrolyzed by the application of heat. Hydrolysis-cleaving complex molecules into smaller one through the addition of a water molecule-occurs when inulin-rich geophytes are baked for an entire day or longer in moisture-rich earth ovens (Thorns 1989; Wandsnider 1997). …