They ate dirt, and they stomped the poison out with their bare feet! The potato. Wild potatoes in the Andes were packed with glycoalkaloids such as solanine and tomatine. The compounds kept pests away, yet they left the raw tubers so bitter and poisonous that eating them could bring on severe cramping, paralysis, or death. Early Andean people dealt with that in two odd ways: they ate dirt, and they stomped the poison out with their bare feet. Geophagy came first. They dipped the bitter potatoes in a slurry of a particular local clay called chaco or pasa. The fine particles bound the toxins in the stomach so the body never absorbed them; they simply passed through. Clay handled the immediate danger. It offered no way to store a large harvest. For that, the Tiwanaku and later the Inca invented freeze-drying and produced chuño, apparently the first such process anywhere. In the high altiplano winter they spread the potatoes on the ground and let them freeze overnight. The cold shattered the cell walls. When the sun rose the tubers thawed. Villagers then walked over them barefoot, squeezing out water and the bitter juices the frost had released. They repeated the freeze-thaw-trample cycle for several days until the potatoes were flattened and dry. To make the paler, refined version known as tunta or white chuño they submerged the tubers in a cold mountain stream for a few weeks so the last toxins could leach out, then dried them in the sun once more. The finished chuño was safe. Moisture and toxins gone, it could sit in woven storehouses for more than a decade without rotting. That light carbohydrate supplied the calories that let vast Andean empires thrive in an unforgiving climate. Potatoes spread across the ground to freeze-dry into chuño in the high Andes. Photo by Chuck Moravec (Wikimedia Commons) is licensed under CC BY 2.0.