Subsistence is one of the factors that determined the presence or migration of prehistoric human populations. At the same time, humans were largely responsible for the dissemination of important crop plants such as maize (Zea mays). Maize is the major domesticated species in the New World, with thousands of landraces that were shaped by environment and human culture. Genetic analyses of archaeological and indigenous maize samples were used to verify the occurrence in South America of at least two major introductory waves of distinct races of maize from its center of origin in Mexico. The first occurred around 5000 years ago and spread primarily through the Andean region. The second one, 2000 years ago, spread through the lowlands of South America. These two distributions may reflect cultural isolation between the regions. In terms of subsistence, the present study found that the maize used by indigenous Brazilian populations, including those in Amazonia, is genetically closer to samples from Mexico than to samples from the Andes. This applies to both the contemporary and the archaeological samples indicating that the inhabitants of Brazil, including those from Amazonia, had a stronger relationship with populations from Central America and northern South America than from the Andean region. An exception can be seen in the region of northern Chile through Paraguay to southern Brazil, where the mixture of the three genetic groups indicates possible cultural contact between highland and lowland peoples. Additionally, the greatest diversity in maize was observed in samples from Roraima state, in northern Amazonia, and this may reflect the fact that human populations of the region had intense contact with different cultural groups, including the Andean groups.

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