China is cheating.
From the New York Times:
"In Chinese newspaper profiles this year, He was listed as 14, too young for the Beijing Games.
"The Times found two online records of official registration lists of Chinese gymnasts that list He’s birthday as Jan. 1, 1994, which would make her 14. A 2007 national registry of Chinese gymnasts — now blocked in China but viewable through Google cache — shows He’s age as '1994.1.1.'
"Another registration list that is unblocked, dated Jan. 27, 2006, and regarding an 'intercity' competition in Chengdu, China, also lists He’s birthday as Jan. 1, 1994. That date differs by two years from the birth date of Jan. 1, 1992, listed on He’s passport, which was issued Feb. 14, 2008."
An admission of cheating in 2000:
"Yang Yun of China won individual and team bronze medals at the 2000 Sydney Olympics and later said in an interview on state-run television that she had been 14 at the time of those Games. A Hunan Province sports administration report also said later that she had been 14 when she competed in Sydney."
China's People's Daily newspaper stating He Kexin's age as 14 on May 23, 2008:
"Olympic gymnastics title contenders suddenly have one more thing to worry about other than the eight gold medals China claimed at the Tianjin World Cup last week. Her name is He Kexin.
"The 14-year-old newcomer to the national team, who was recruited last year, has raised a lot of eyebrows recently after she broke two world records on the uneven bars in as many months. She will be just one more weapon on an already star-studded Chinese Olympic squad."