The remnants of the legendary Shu dynasty may be the last remains of worshippers of an all-powerful sun god, a Southeast Asian tribe that took a wrong turn, or even, according to some, a civilisation inspired by aliens. The mysteries surrounding China's most famous burial site have yet to be fully solved but archaeologists shifting through the evidence have already gathered enough to begin rewriting the nation's history books. Unearthed in 2001 by a development company digging in the Chengdu suburbs, Jinsha is not much to look at. A series of holes in the ground surrounded by scrubland, the only indication of its value is the skeleton of a hanger-shaped museum being erected over the top of it. When finished, it is hoped the onsite museum will rival the famed terracotta warriors that guard the tomb of the first Qin emperor Shi Huangdi. Possibly dating back as far as 3,500BC, to the late Neolithic age, the site has yielded fascinating finds such as exquisitely designed bronze sacrificial vessels of a calibre far exceeding contemporaries in the ancient Middle East. There are also pieces of polished jade fashioned into axe heads, and most curiously, stretched stone faces carved with Spock-like pointy ears and ornate headdresses. Unlike anything seen before, these faces have come to symbolise the archaeological excavations in the area, both at Jinsha and in nearby Sanxingdui, 40km north of Chengdu in the town of Guanghan . But it is what these sites represent as centres of ancient civilisation that excites historians. Popular history has always believed that Chinese civilisation originated in the Yellow River area with the Xia and Shang dynasties. It was from these dynasties that the first examples of Chinese script were found, as well as the beginnings of a hereditary leadership system distinct from an earlier practice of chieftain elections. The digs in Sichuan confirmed what many archaeologists already suspected - that Chinese civilisation has multiple origins. 'Originally we only knew about the ancient Shu culture from tales in the later Qin and Han dynasties,' said Jiang Zhanghua, from the Chengdu Institute of Archaeology, referring to a legendary dynasty that is now believed to have had its capital at Sanxingdui. 'From the stories, we never knew anything substantial. These stories simply mentioned certain kings and their personal traits. Now we understand their history and know that the stories are true.' Roughly corresponding to present-day Sichuan, the Shu dynasty was governed from a capital both physically impressive and materially wealthy. Encircled by a 12km clay wall, indications are that Sanxingdui was a bustling centre of trade. Cowry shells from the south China coastline, elephant tusks from Southeast Asia, and minerals alien to Sichuan, such as copper, tin and lead - used in bronze making - all suggest a sophisticated barter or possibly even currency system was in operation, while the presence of clay tripods used as wine vessels, and decorative clothing carved on the unearthed statues, suggest a predilection for the good life. What is unclear is how the ancient Shu discovered how to fire clay and mould bronze to such intricate levels. Some believe they were in regular trading contact with tribes along the Yellow River, while others postulate a central Asian influence. What is accepted is that the area was a centre of culture and civilisation in its own right. Society was structured and class level was instantly recognisable by clothing and hairstyle - long queue for workers, tied bun for the elite. Believed to have been monotheistic in their worship of a sun god, excavations at Sanxingdui and Jinsha have revealed a world rich in religious symbolism and ritual. The most spectacular of these is a giant golden tree standing almost four metres high, with dog-headed serpents snaking their way up its trunk. On each branch sits a giant bird, which legend has it carried the sun on its back across the sky. Tree worship was also a common trait of tribes in Mesopotamia - modern-day Iraq - but experts remain cautious about suggesting that one culture influenced the other. At Sanxingdui, a site that predates Jinsha, jade and golden ornaments are believed to have represented offerings, and the discovery of turtle shells are thought to mark a predilection for divination. It is hypothesised that the city's ruler was responsible for both spiritual and temporal affairs, but without any written records researchers are often left to make guesses. It is a lack of written evidence that has given rise to some of the more bizarre theories on the internet about the origins of these cultures. First discovered in 1929 by farmers digging a drainage ditch, Sanxingdui has been rumoured to be the offshoot of an extraterrestrial civilisation. Presumably inspired by the Star Trek-style face carvings, the alien theory is given an additional twist by the mysterious abandonment of the city around 3,000 BC. While some suspect a disease or flood wiped out the city, archaeologist Sun Hua of Peking University has his own theory. 'Sanxingdui culture ended due to conflict with outside forces,' Professor Sun said. 'The idea of a flood is not feasible because at that time the geography of the area would not have made it possible. And if there were a disease then there would be more bodies.' In explaining what happened to the citizens of Sanxingdui, the discovery of Jinsha offered new clues, said Mr Jiang of the Chengdu Institute of Archaeology. Having spent more than 20 years investigating the two sites, Mr Jiang said Jinsha was an amalgamation of Sanxingdui refugees and tribes from further down the Yangtze River. Holding open a book detailing the shapes of prehistoric wine amphora, Mr Jiang said the combination of both round-bottomed vessels favoured in Sanxingdui and flat-bottomed containers from what is now Hubei indicated a blend of the two Yangtze River cultures. His theory helps explain why at the time of Sanxingdui's sudden demise, the population of Jinsha appears to have risen. As for the masks, with their bulging eyes and other-worldly ears, nobody can offer a satisfactory explanation. 'Maybe Europe, maybe central Asia,' said Mr Jiang. Could they have come from a distant galaxy? 'Unlikely,' he said.