BEIJING, March 12 (Xinhua) -- Scientists using a new radioactive dating method have found that "Peking Man," or Homo erectus who was believed to live in the Zhoukoudian Caves in suburban Beijing 400,000 to 500,000 years ago, is actually 200,000 years older, according to a scientific journal published Thursday.

    Guanjun Shen from the Nanjing Normal University in eastern Jiangsu Province and his colleagues used an upgraded method based on the radioactive decay of aluminum (Al) and beryllium (Be) isotopes in quartz grains to carry out the dating process. The new results showed that the tool-making "erect man" could be dated back as early as 770,000 years ago.

    Shen said the average margin of error of this new method could be plus or minus 80,000 years.

    Their research finding was published on the Thursday issue of London-based science journal Nature.

    With the older age, "Peking Man" should be living in the area through glacial to inter-glacial cycles, not just in the inter-glacial period, when it was a lot warmer, according to the paper.

    To date, the majority of habitat sites for erect men, or ape men were found in areas with low latitudes and warm climates such as south China, South and East Africa and Indonesia. But "Peking Man" was an exception.

    "A colder climate would bring huge challenges to the survival of Homo erectus," said Gao Xing, a scientist from the Institute of Vertebrate Paleontology and Palaeoanthropology, and one of the paper's co-authors.

    "So our research might open a new subject for the international community of palaeoanthropologists to think about how erect men adapted to cold weather."

    The earlier conclusion about "Peking Man" living 400,000 to 500,000 years ago was made by Chinese scientists based on the age estimates of animal fossils unearthed at the same time as the bonefossils of "Peking Man" 80 years ago, Gao said.

    Uranium-series dating confirmed that the age estimate for layers where the "Peking Man" was unearthed were about 500,000 to 600,000 years old. But with a short decay cycle, Uranium-series could only be used to date things younger than 600,000 years, Gao said.

    He said the new method they used has proved more accurate than U-series dating when used for age estimates of Homo erectus in South Africa in 2003. The research finding was published on the American journal Science.

    "We knew immediately that it could be a better method to check the age of 'Peking Man'," said Gao.

    He said that his team were also able to date the animal fossils to a more accurate age, which were also about 200,000 years older.

    Chinese archaeologist Pei Wenzhong found the first complete human-like ape skull in Zhoukoudian, about 50 kilometers southwest to the center of Beijing, in December 1929.

    In 1936, technician Jia Lanpo, who later became an archaeologist, excavated three other Peking Man skulls in succession.

    Gao said that Chinese researchers would start looking for traces of other groups of erect men in those unknown caves around Zhoukoudian this spring.