Ancient Savannah Roots of the Carbohydrate Revolution in South-Central North America

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.