In 1996, a state project was launched to determine the chronology of early Chinese history in the Xia (2070-1600BC), Shang(1600-1046BC) and Zhou(1046-256BC) dynasties. The project aimed to draw a clear, and coherent picture of China 's beginnings. On November 10,2000, the initial research results after nearly five years' strenuous work made public.

Chinese ancestors who lived 3,000 years ago left a huge puzzle for their descendants to work out before leaving this world . The puzzle is made up of scrambled clues from scattered writings and oral legends but there are some missing pieces as well. For five years, more than 200 Chinese historians, archaeologists, astronomers, physicists and other scholars have put their heads together to sort the puzzle out and develop a chronology of early Chinese history. The project, which has won a special research grant from the Ministry of Science and State Administration of Cultural Relics, is known as the Chronology of Early Chinese History in the Xia, Shang and Western Zhou dynasties. After five years' work , the researchers announced on November 9, 2000 in Beijing that they had achieved initial research results, discovered many missing pieces and sorting out some of the puzzle. According to Li Xueqin, the chief historian leading the project, the scholars have been able to ascertain that the earliest Chinese dynasty, the Xia, existed for about 470 years between 2070 BC and 1600 BC. The Shang Dynasty, which followed the Xia, is now divided into the earlier(1600-1300 BC) and the later periods (1300-1046BC) ,according to researchers. The years of the reigns of the 12 monarchs of the later Shang Dynasty and all the 13 monarchs of the Western Zhou Dynasty(1046-771 BC) have been ascertained. Above all , researchers have been able to pinpoint the years when King Wu waged a decisive battle against the last king of the Shang Dynasty . The year 1046 BC was the year when ancient Egypt, in the Tanite 21 st Dynasty(1085-945 BC), was losing control of its Asiatic empire; when successive kings of the 2ed Dynasty of Isin(c.1000-500 BC) to witness ever more cultural prosperity.

The initial research results indicated that the earliest ascertained period in Chinese history goes back more than 1,200 years than previously thought . But it has been a daunting and hard task to solve the puzzle and see the overall historical picture. Sima Qian(145 or 135BC?) , a great historian who lived in the Western Han Dynasty(206 BC-AD 23), delved into historical record, visited areas where great events documents in earlier annals were said to have taken place and talked with people who were old and learned. But he still found it difficult to sort out the puzzle before the year 841 BC, when the 10 th king of the Western Zhou Dynasty was forced to give up his rule to two respected royal dukes after widespread uprisings in the country. A systematic and scientific approach to sorting out the historical puzzle was designed. After examining the existing clues and broken pieces, they divided the work into nine research branches and 44 topics. Individual research accomplishments in the fields of history, archaeology, astronomy, mathematics and physics since early on un the archaeologists conducted or expanded scientific excavations at some 15 sites in Henan, Hebei ,Shanxi and Shaanxi provinces and Beijing as well. The researchers have harvested many relics that relate to monarchs in the Shang and Western Zhou dynasties. Although only a few pictographs have been found inscribed on bronze ware from tombs of the Xia Dynasty, more than enough ruins and relics now prove the existence of the Xia Dynasty. The historians have also studied the dates engraved on 60 bronze containers, which were once used in the Western Zhou Dynasty. The dates became important clues for ascertaining the chronology of the kings in the periods. Meanwhile, philologists have searched nearly 400 ancient Chinese annals and collected written records, and gathered “clues” recording astronomical events and indicating the locations of earlier dynastic capitals. During their researches, astronomers looked at celestial phenomena that happened thousands of years ago, especially the solar and lunar eclipses Chinese ancestors recorded piously in ancient classics that were often associated with important political events such as ascension of a king or the demise or defeat of another king. By correlating the astronomical data with the modern calendar, they helped create a rough time framework for kings in the later period of Archaeology of the Chinese Academy of Social Sciences also joined the project .They collected samples from human bones and tiny parts from animal bones bearing the earliest Chinese characters, the jiaguwen (oracles bones), all unearthed from tombs proven to belong to the Shang and Western Zhou dynasties. They then conducted scientific carbon dating via radiocarbon dating equipment and an accelerator for the time frame of the historical periods. For each of the years, the researchers first determined that results from historical records, archaeological evidence, astronomical calculations and carbon dating techniques tallied and correlated before putting the ascertained piece into the chronological puzzle.

The new chronology of early Chinese history is by no means the first in Chinese history. Liu Xin(?-AD23), a historian, founder of the school studying classical Chinese writings and an astronomer, wrote the first chronology of Chinese history in the later years of the Western Han Dynasty(206 BC-AD 23). Despite the achievements, the researchers involved in the project agreed that the bigger puzzle about the political, social and economic development of the early Chinese dynasties is far from complete.

The four ancient civilized nations in the world refer to ancient Egypt, Babylon, India and China, which were considered an the earliest entry from primitive society into slave society. They were the cradles of civilizations of the world.