Evolutionary and food supply implications of ongoing maize domestication by Mexican campesinos

Maize evolution under domestication is a process that continues today. Case studies suggest that Mexican smallholder family farmers, known as campesinos, contribute importantly to this, but their significance has not been explicitly quantified and analyzed as a whole. Here we examine the evolutionary and food security implications of the scale and scope under which campesinos produce maize. We gathered official municipal-level data on maize production under rainfed conditions and identified campesino agriculture as occurring in municipalities with average yields of ≤ 3 t/ha. Environmental conditions vary widely in those municipalities and are associated with a great diversity of maize races, representing 85.3% of native maize samples collected in the country. We estimate that in those municipalities around 1.38 x 1011 genetically different individual plants are subjected to evolution under domestication each season. This implies that 5.24x108 mother plants contribute to the next generat...