Chinese history can be traced back over 5,000 years to the Neolithic period. The earliest known Chinese civilisation began in the fertile basin of the Yellow River in the north of China. This civilization was known as the Yangshao culture, which flourished between 5000 and 3000 BC. The Yangshao people lived in small villages and built simple houses of mud and timber. They grew crops, such as millet and wheat, and kept animals, such as pigs and sheep. They also made pottery and tools of stone and bone. The Yangshao culture was followed by the Longshan culture which lasted from around 3000 to 2000 BC. The Longshan people lived in larger settlements and built more sophisticated buildings, including some made of stone. They also developed a system of writing and made advances in metallurgy.