The ancient Chinese civilization grew along the Huang Ho river valley beginning in the Stone Age. Early tribes practiced organized farming and built circular houses with conical roofs and mud floors. Archaeological evidence shows the remains of ovens, storage rooms, and kilns indicating progress in agriculture. Writing also developed during this period, featuring a unique pictorial script where each symbol represented a word and text flowed from top to bottom. This led to the emergence of cities, specialized crafts, long distance trade, and strong central government.