Drivers who frequent the one major road in the little-visited western part of the Tibet Autonomous Region all know, or at least have heard of, one man, and when they see him walking, they stop and ask if he wants a lift.

Why? They say if you have to spend two weeks driving somewhere, Tang Rongyao, 36, is the best person to talk with. He tells the drivers stories about the sparsely scattered houses on the plateau in which he spent his nights and his latest findings of the "lost kingdom." In return, the drivers point out what they believe to be clues to the kingdom's existence along the way. 

Tang, who was previously a business journalist at a newspaper in Yinchuan, capital of Ningxia Hui Autonomous Region, prefers to be known as a "private archaeologist." He has put all his spare time and life savings for the past six years into researching the remaining population of the Xixia Kingdom (Western Xia, 1038-1227). 

The kingdom, established by the Dangxiang clan (Tanguts) in the northwestern part of the country, had territory overlapping today's Ningxia Hui Autonomous Region, as well as parts of neighbouring Gansu and Shaanxi provinces and the Inner Mongolia Autonomous Region. After it was crushed by the army of Genghis Khan, the kingdom left behind little more than a few pyramids in desolate land and hieroglyphic writings, of which no one was able to read one word until the past century.

But Tang believes the ancient clan still has its modern descendants. In his recent book titled "Fading Away of a Kingdom," he proposed that the Sherpas in the Himalayas, who earned fame as guides to the world's highest peaks, are descendants of the Western Xia.

He reached the conclusion after travelling throughout the 12 Chinese provinces and regions that were part of the kingdom. It wasn't until 2004, when he arrived at tiny Sherpa communities at the foot of the Himalayas on the Qinghai-Tibetan Plateau after 30 days of walking and taking lifts, that he thought himself to be on the verge of a real discovery. He went back twice afterwards to confirm his suspicions.

The Sherpas, with whom he stayed for two months, shared with him their ancient art and architecture and their customs and legends. In a lamasery in one of their villages, a 97-year-old Living Buddha recounted stories of their ancestors who migrated, in an arduous trip across snow-capped mountains and no-man's lands, from their riverside cities in the east to the depths of the Himalayas. 

"Our ancestors used to have a kingdom," the Buddha told Tang, "and they battled all the way from there to this peaceful place after they lost it."

Exhilarated at his discovery, Tang was also convinced that people would hardly believe him. "I don't care if the established historians nod their heads or not," he said. "Most historians have never traveled as extensively as I did."

But the historians were more open-minded than he thought. Chen Gaohua, the country's foremost historian who is an academician at the Chinese Academy of Social Sciences, said: "There is a possibility this private archaeologist is correct, but he needs much more evidence to support his theory."

In their escape, the surviving Tanguts could have chosen to go southwest and joined the Tibetans, with whom they share a religion and have similar ethnic origins. In extreme conditions, they could have crossed the plateau from the north to the south and settled in the Himalayas, said Chen, who added that he was merely speculating on the Tanguts' tragic migration.

It was this migration of the kingdom's survivors, who fought and died or went farther from their homeland, that attracted Tang's interest most and finally got him to start his private research. As a result, he has been left without money and remained single when his peers all have children.

"I was lured by the mystified tragedy of the kingdom and its people," he said. "In the back of my mind, I have always wanted it to have a happy ending, like its descendants' living in a Shangri-la."

Before, Tang was leading a typical life of an upwardly mobile professional and had little interest in historical research or Tanguts until he found a job in Yinchuan, Ningxia's capital, in 2000 and visited the pyramids containing the Tanguts' kings' tombs in the city suburbs one weekend.

Tang, who loves reading and writing poems, cried when he saw the nine magnificent pyramids standing in the vast plain in the sunset, with the Helan Mountains in the background and the Yellow River roaring by.

Returning downtown, he looked for books about the Xixia Kingdom at libraries. He was so keen on the topic that he read almost all the important Chinese-language research papers about it in the ensuing two years.

But after reading, Tang felt unsatisfied. "Many historians are simply copying one another," he said. "I will do what they failed to travel."

He began to follow possible migration routes of the founders of Xixia and those of the kingdom's survivors. Actually, he traveled so much that his newspaper, the Yinchuan Evening News, shifted his beat of coverage from finance to archaeology. His boss agreed to let Tang fax his stories to the editorial office, but he has to pay his own travel expenses most of the time.

Tang knows how to save money. His friend, an oil tanker driver who often goes between Yinchuan and Lhasa, introduced him to other drivers, and in the end Tang became friends with more than 100 drivers of all kinds of trucks traveling on the Qinghai-Tibet Plateau.

During his trips, he met a Sherpa from time to time and began to suspect that the Sherpas, whose origin remains unknown, are actually descendants of the Tanguts. When he finally decided to visit the Sherpa villages at the beginning of 2004, he had to wait four months before two of his driver friends called him from Gansu in April.

They said they were going to drive an oil tanker to Xigaze, Tibet. Upon receiving the call, Tang took a bus to Gansu and walked 10 kilometres to the small village where the drivers lived. He stayed at their home for three weeks before they started.

It took 10 days to drive from Lanzhou, Gansu's capital, to Xigaze. From there Tang walked and hitchhiked for 20 days until he reached the Sherpa villages of Lixin and Xuebugang in the Himalayas, which are northwest of Zham Town, on the border between China and Nepal.

In several lamaseries along the way, Tang found frescoes portraying people holding peonies. Peonies, growing in the Yellow River Valley, were the favorite flower of the Tanguts. They appeared in many relics of the Xixia Kingdom, ranging from paintings and frescoes to pottery and gold objects.

Following what he called "the peony route," Tang became more and more curious about the Sherpas. The Sherpas he met on the way told him that the word "Sherpa" means "people from the east," and that their ancestors migrated to Tibet centuries ago from an unknown place.

He finally made his way to Lixin, a Sherpa village about 4,000 metres above sea level. The Sherpas call it Yitulu, meaning "where white flowers blossom."

Stepping into the lamasery at the village, Tang said he gasped. There it was, at the entrance of the lamasery a giant statue of the "Sensual Buddha," showing a goddess mounting Buddha in their "double meditation." The two wore their hair and clothes in the Tanguts' style. 

"It can be understood that procreation became the top priority of the Tanguts after they had traveled such a long and arduous way to get there," Tang surmised.

Beside the "Sensual Buddha" stood the statue of a man who was also dressed in the Tanguts' style, at least in the eyes of Tang, similar to the murals found from the Xixia ruins in Yinchuan. Holding a volume of scriptures in his right hand, he had a sad, concerned look.

The 97-year-old Living Buddha at the lamasery, whose name is Baima, told Tang that even he didn't know what was special about the statues. "They were handed down by our ancestors," he said, "and we worship them as our ancestors did."

In another conversation, Tang said Baima told him: "Our ancestors said that we used to have a kingdom at some place in the north, which was very far away. On the way from escaping from fierce enemies, they founded the city of Qamdo (Changdu, east of Lhasa), which means 'where we battled' in our language."

In Tang's eyes, the Sherpas' adoration of the white colour, their marital customs and festivals all hinted at their origin in the Xixia Kingdom. Even their practice of concealing their family names added to his evidence.

"We Sherpas memorize our family names," said Pasang Norbu, a veterinarian in Zham. "We will never use them, but we tell them to the girls we prepare to marry so that the husband and wife will not come from the same large family."

To decipher the mystery, Chen suggested that the easiest way is to compare DNA samples in the remains of ancient Tanguts and those in the modern Sherpas.

But Tang said he was not ready to relay the suggestion. He would prefer the Sherpas live in peace in the remote villages where trees of red roses grow taller than people and incredible snow-capped mountains are reflected in sheltered lakes.