At almost all Nok sites, there are charred plant remains consisting of firewood and plant material for cooking. Remains of pearl millet, one of Africa's oldest grain crops, are commonly found. Pearl millet is highly productive and resistant to adverse growing conditions, including drought. Cowpeas, valued for their high protein content, are also found at some sites. So far, pearl millet and cowpeas are the only crops known to have been cultivated by the Nok people. It is unclear whether they ate or farmed tubers of any kind. The numerous grinding stones found at Nok sites suggest that the grains were ground into flour and made into a type of porridge.