Selecting plants in the valley
Wild teosinte, a close relative of maize, grows in the Balsas drainage of Mexico. Early inhabitants gathered and processed local plants and increasingly cultivated selected seed. Repeated planting and harvesting accumulated changes over generations in grain, ears and growth. Maize developed among several foods rather than replacing all other resources at once. Tool use, seed selection and seasonal labor formed connected activities, requiring households to organize cultivation alongside gathering and storage.
Small traces preserved on tools
Tools and sediments at Xihuatoxtla shelter preserve starch grains and phytoliths. Comparisons with modern plants identify early maize use, while dating and stratigraphy place relevant activity around 8,700 years ago. Residues on grinding stones connect plant evidence with food preparation. Occupation layers and other tools provide context for the small remains. Together these materials allow researchers to relate changes in the crop to the work of people living in the valley.
Cultivation travels with the crop
Maize later spread into different environments, where cultivators selected types suited to local seasons. Exchange and migration carried seed, equipment and processing knowledge. Communities combined maize with beans, squash and other resources, organizing fields, harvests and stores. Later towns and states drew supplies from such farming, and maize entered ceremony and narrative. Continued selection produced regional varieties and preserved seed and knowledge adapted to diverse conditions.