Up on the high plateau of the Bolivian Altiplano around Lake Titicaca, where the potato was domesticated, the Aymara people eat their potatoes with a light white clay called p’hasa. Samples obtained by Panama-based geologist Dr Stewart Redwood show the clay contains two forms of the mineral montmorillonite – fuller’s earth and bentonite – both much used in industry today for their ability to bind to unwanted material by adsorption and absorption and prevent its chemical activity. This binding ability, he says, would have solved the problem of the bitter and potentially toxic solanine found in green-skinned potatoes. Later it would be bred out, but at the outset the clay would make it possible to eat potatoes and start the process of domestication that has made them the world’s fourth most important food crop today.