3400 years of agricultural engineering in Mesoamerica: lama-bordos of the Mixteca Alta, Oaxaca, Mexico

The origins of early Mesoamerican agricultural techniques are not well established. Our charcoal-derived radiocarbon chronology dates cross-valley check dams, or lama-bordos, buried by up to 11.5 m of sediment in arroyos near Coixtlahuaca, Oaxaca, Mexico. Now it is clear that people in highland Mexico built lama-bordos at least 3400-3500 years ago, several hundred years earlier than previously dated engineering systems in Mesoamerica. Lama-bordo systems evolved as intensively and extensively managed landscapes coeval with climate shifting to more arid conditions. They provide clear examples of human-produced stratigraphy and artificial landscapes (stair-stepped valleys). More importantly, these lama-bordo systems signal a major cultural tipping point toward sedentary agricultural life and solidify our understanding of the Neolithic transition in Mesoamerica.