China is a vast country with a huge range of terrains and climates within it. As well as the country’s sheer size, geographical features such as mountain ranges, deserts and coastlands have all helped shape Chinese history. Above all, the great river systems of China, the Yellow River to the north and the Yangtze to the south, which have given Chinese civilization its distinctive character.
The Yellow River region
The civilization of ancient China first developed in the Yellow River region of northern China, in the 3rd and 2nd millennia BC. A large part of this area is covered by loess soil. This very fine earth has blown in from the highlands of central Asia over thousands of years, and makes one of the most fertile soils in the world. In ancient times, the main crop in northern China was millet, a highly nutritious food still grown in many parts of the world as a major crop.
The Yangtze Valley region
To the south, the great Yangtze valley, with its warm, wet climate, was the first area in the world where rice was grown, sometime before 5000 BC. From this region rice cultivation spread far and wide across southern China and into south-east Asia.
Rice is one of the most nutritious plants known to humans - three or four times as nutritious as wheat. This means that, other things being equal, a much larger number of people can be supported from the same area of land with a rice crop than with a wheat crop.
Most of the history of Chinese civilization, including the ancient period, has traditionally been divided into dynasties. A dynasty is a line of kings or emperors from a single family, following each other on the throne from generation to generation. In Chinese history (in contrast to European history) the succession was, in the overwhelming majority of cases, from father to son. This was because, due to the dictates of ancestor worship, it was a ruler's overriding responsibility to produce a male heir. Not to have done so would have been unthinkable.
At times throughout Chinese history, the huge country has been united under a single emperor. At other times, several competing dynasties have divided the country between them. It is only the ones who have ruled the entire country, however, which have been accorded true legitimacy by Chinese historians.
The situation in ancient China was slightly different, in that for much of the ancient period what would later be known as "Chinese civilization" was only gradually spreading across the area which today we know as "China". Thus the early dynastic rulers of China are known as kings, rather than emperors. It is only after the time of the First Emperor, Qin Shih Huang, who reigned over a united China from 221 BC, that the imperial period of Chinese history began.