Many such practices continue today, as well as showing up in the archeological record, but masonry ovens like the ones we know now only appear with the start of grain agriculture — in other words, bread (and beer — which is the likely source of the yeast used to make the first bread rise). Ancient Egyptians left drawings of bakers putting dough on a hot rock and covering it with a hot clay pot — the first “true” oven. Over time, the single-loaf ovens grew large enough to bake multiple loaves, and construction practices expanded from holes in the ground to clay pots to brick and rock domes and vaults.