Hardwood ash nixtamalization may lead to false negatives for the presence of maize by depleting bulk δC in carbonized residues

Among the multiple proxies for detecting maize in precontact economies is the use of δ¹³C analysis of carbonized residues from ceramic cooking vessels. Although maize horticulture was widely established in Eastern North America (ENA) by A.D. 1000, there are carbonized residues from ceramic assemblages after this date that lack the elevated δ¹³C values indicative of the presence of maize. This may be due to the true absence of maize, or other factors including the masking of maize. Prior experimental research by Hart et al. demonstrated that the addition of C₃ plants or consumers to two part mixes with maize can mask maize presence even when maize is the dominant ingredient. Here we investigate the effect of alkali processing of maize (nixtamalization) on δ¹³C using the widespread ENA process of boiling maize kernels with wood ash, a C₃ product, to create hominy. Our experiments test whether or not the process of hardwood ash nixtamalization can mask the presence of maize in adhering carbonized residues by depleting δ¹³C values, and whether there is a reciprocal δ¹³C enrichment effect on the hardwood ash employed in nixtamalization. Overall, there is substantial δ¹³C depletion of residues when maize is cooked with hardwood ash, and hardwood ash cooked with maize shows the reciprocal enrichment. Therefore, the depleted values after the adoption of maize may be false negatives due to the nixtamalization process.     

Pottery wall thinning as a consequence of increased maize processing: a case study from central New York

The histories of maize in northeastern North America are not well understood at the subregional level. The complexity of formation processes for various lines of evidence for maize use requires the application of many analytical methods and techniques to produce data on subregional maize histories. The present analysis uses bulk δ¹³C values on directly dated charred encrusted cooking residues to provide the first direct correlation of water-based maize cooking to trends in pottery wall thinning. The results add to the growing body of evidence for the history of maize use in central New York.     

Guanaco (Lama guanicoe) isotopic ecology in southern South America: spatial and temporal tendencies, and archaeological implications

We synthesize and discuss available isotopic data on Holocene guanaco samples from southern South America, extending from Tierra del Fuego Island to northern Patagonia and the Pampean region. We evaluate temporal and spatial tendencies on the basis of 91 samples (mainly based on δ¹³C_collagen values), presenting implications for paleodietary research in archaeology. We conclude that there are no strong correlations with latitude in the macro-spatial scale, while there is a set of interesting patterns at smaller regional scales. These patterns lead us to evaluate the role of ecologic and topographic variables (e.g. canopy effect, variations in altitude, ecotones) in structuring isotopic variability. Finally, on the basis of the present analysis we suggest a number of hypotheses and perspectives for the use of stable isotopes as geographic tracers of guanaco distribution in the past, and specific implications for the paleodietary study of human samples.     

Studies on amerindian dogs, 1: Carbon isotopes in relation to maize in the diet of domestic dogs from early Peru and Ecuador

Work initiated purely as a dating project in support of a craniometric and morphological investigation of domestic dogs from early Peru has proved to have much wider implications. The stable carbon isotoperatios (¹³C/¹²C) of hair samples from ten dogs show that maize formed a significant part of their diet. Radiocarbon dates for these remains have confirmed that they belong to the period well after the cultivation of maize was first established. Stable carbon isotope measurements can thus be used to test for the presence of maize as a dietary constituent at earlier sites even where there is otherwise only indirect evidence for its cultivation. Collagen from animal or human bone is a suitable alternative to hair for this purpose and the method has been successfully applied to collagen dating to c. 3000 BC from the Valdivia culture site of Real Alto, Ecuador, as well as to a series of early Peruvian dogs.