China apes in decline

Loss of world's rarest ape charted

Historical Chinese documents have helped scientists to track the decline of the world's rarest primates.

Today, China has between 26 and 28 Hainan gibbons left, but government records that date back to the 17th Century show that gibbons were once widespread across half of the country.

The apes began to disappear from the documents about 150 years ago, corresponding with population growth.