A fossilized occipital bone of the 5,000-year-old Peking Man, who lived in what is now Zhoukoudian area on Beijing's southwestern outskirts, went on show Thursday for the first time since its discovery 37 years ago.

The occipital bone, discovered on May 4, 1966 under the direction of Pei Wenzhong, the late Chinese archeologist, is the one of the two pieces of skull fossil of Peking Man in China. It will be put on display at the Zhoukoudian Peking Man Site Museum from Thursday till Oct. 14.

The occipital bone is almost as big as the palm of a human being. The museum has bought insurance of 4.5 million yuan (about 542,000 US dollars) for showing this bone fragment and policemen will also guard the bone throughout the exhibition.

"It is one of the best clues scientists have to the prehistoric hominid," said Gao Xing, deputy director of the ancient vertebrate and ancient human research institute under the Chinese Academy of Sciences.

Chinese archaeologists unearthed the first skull of Peking Man at Zhoukoudian, 48 kms southwest of downtown Beijing, in December 1929. The discovery stunned the world.

Gao Xing acknowledged that five complete skulls of Peking Man had been unearthed at the site by 1937 since the excavation of the Peking Man site started in 1927. Besides the three teeth of Peking Man stored in a lab in Sweden, the other five skulls mysteriously disappeared during the World War II and no trace of them has been found.

The other Peking Man skull fossil is a frontal bone, which was exhibited in September last year.

Excavation of the Peking Man site resumed after the founding of new China in 1949 and, to date, Chinese archaeologists have unearthed fossils belonging to 40 Peking men, more 100,000 items of stoneware, traces of fire use and large quantities of fossilized vertebrae.

China put the site under top state protection in 1961, and in 1987 it was included by the United Nations Educational, Scientificand Cultural Organization (UNESCO) on the World Heritage list.