With the change from hunting-gathering to agriculture after the last ice age ended twelve thousand years ago and the need to store and boil seeds for FOOD, pottery-making soon evolved into a specialized craft. Originally pottery was made by building up coils of clay and forming the succeeding layers of the coils into an even wall. This type of coiling requires turning the pot slowly as the work proceeds, so early potters would begin the coiling on a flat plate which they could rotate by hand. This technique is still being used by some primitive potters in African and Asian villages, who then fire their finished ware after drying by piling it on brushwood and burning it in a bonfire. Potters wheels were invented in Mesopotamia (now Iraq) about 4000 BCE, when the Sumerians - the first town- and city-based civilization on earth, arose and flourished. The Sumerians were the first civilization to use wheels to construct carts (previously heavy loads were dragged on sledges, or over rolling logs) and chariots. They also were the first to invent turntables for making pottery, although these early potters wheels were not free-running like modern wheels - they merely permitted faster and more efficient coiling. Paintings in Egyptian tombs dated 3000 BCE show potters working with turntables made from stone or wood. The development of pottery wheels or turntables rapidly increased pottery production, and the process came to be dominated by male potters who specialized in the craft rather than females working at the task in free moments.