Humans built masonry ovens long before they started writing. The process began as soon as our ancestors started using fire to cook their food, probably by spit-roasting over live flame or coals. Big starchy roots and other slower-cooking foods, however, cooked better when they were buried in hot ashes, and sometimes covered with hot stones, and/or more hot ash. Large quantities might be cooked in an earth oven: a hole in the ground, pre-heated with a large fire, and further warmed by the addition of hot rocks.