Beardless warriors had been discovered among China's terracotta army, providing evidence of the youthful ages of some soldiers when the army was created more than 2,000 years ago.

"Some warriors have no beards, but for ancient Chinese, facial hair was part of the culture, so those warriors could be considered to represent soldiers under 17 years old," said Yuan Zhongyi, honorary curator of the Museum of the Terra-cotta Warriors and Horses of Qin Shihuang, in northwest China's Shaanxi Province.

At the time of Qin Shihuang (259 BC-210 BC), first emperor of a united China from 221 BC, beards were signs of status, and adults without beards were considered to be social outcasts, Yuan said.

Cutting off the beard was a punishment for criminals, he said.

Each warrior had a unique face and expression and most had beards, Yuan said. Fewer than 10 of the more than 1,000 warriors discovered had no beard.

"Many warriors lost their vivid facial expressions over time, but a young warrior holding a spear in the first pit still looks extremely spirited," he said.

Others with sparser beards and baby faces were also considered to be youthful soldiers by experts. A young standing warrior pulling a bow in the second pit might be one of the juvenile soldiers, Yuan said.

The research was revealed at a commemoration of the 35th anniversary of the discovery of Qin Dynasty (221 BC-206 BC) Terra Cotta Warriors in Xi'an, capital of Shaanxi.

It was not usual for ancient Chinese rulers to recruit teenagers under the aged of 17, but historical documents showed that in the Changping Battle, in which Qin kingdom defeated the Zhao kingdom, all men over the age of 15 were recruited, said historian Wang Zijin, of the Remin University of China (People's University of China) in Beijing.

Men aged 17 to 60 could be recruited under Qin law and the discovery of the juvenile warriors supported the historical records, Wang said.

The discovery also reflected Qin power as it could motivate the entire population to defeat the other six kingdoms -- the Han, Zhao, Wei, Chu, Yan and Qi -- to unite the country, he said.

Zhang Mingqia, secretary-general of Chinese Qin and Han Dynasty History Society, said that later in the Han Dynasty (206 BC-220 AD), the children of dead bodyguards of the emperor were trained to be young warriors as an independent guard troop to ensure the safety of the emperor.