The use of ash as a possible precursor of nixtamalization in western Mesoamerica

Ash contains calcium, potassium and magnesium oxides that when combined with water generate hydroxides. Ash was used by human populations in the Pre-ceramic period to tan skins, make garments and footwear, cure wounds, apply tattoos and perform mummifications. We wondered if the application of ash could enable the consumption of grains and seeds of wild maize, beans and squash, and if the treatment with lime could arise from the procedure with ash. We conducted an ethnobotanical study for two years in an area with wild maize, beans and gourds among traditional peasants who cultivate milpa. We recorded the thermo-alkaline treatments related to the consumption of wild grasses, legumes and oleaginous plants. We observed four: three with ash and one with lime. We noted that these ash treatments allow the consumption of wild maize, beans and squashes and form a diet with carbohydrates, proteins and fatty acids with a complete amino acid profile. This could encourage interest in these species and lead to their domestication. The treatment with lime can be regarded as a technological innovation to the ash procedure. It is possible to trace a sequence in terms of energy cost and complexity in five levels, which is related to the domestication process of the three crops. However, it is necessary to experimentally demonstrate the changes in the nutritional characteristics of the wild plants when applying the thermo-alkaline methods with ash.