But US experts say it is not all that difficult. One doesn't have to sift one's way through Chinese passports of birth certificates. X-raying the athletes would resolve the issue satisfactorily, they assert.
Friday the International Olympic Committee ordered an investigation into mounting allegations that Chinese authorities covered up the true age of Kexin because she was too young to compete.
An IOC official told The Times Online "discrepancies" have come to light about the age of He Kexin, the host nation's darling who won gold in both team and individual events.
The investigation was triggered as a US computer expert claimed to have uncovered Chinese government documents that he says prove she is only 14 - making her ineligible to compete in the Olympics - rather than 16, as officials in Beijing insist is her age.
Mike Walker, a computer security expert, told The Times how he tracked down two documents that he says had been removed from a Chinese government website. The documents, he said, stated that He's birth date was January 1 1994 - making her 14 - and not January 1 1992, which is printed in her passport.
He's true age has been a subject of swirling controversy since the Games began. Questions over her eligibility intensified after she edged out the US gymnast Nastia Liukin for the gold medal in the uneven bars on Monday, and was part of the team gold triumph last week. She also edged Britain's Beth Tweddle out of the medals.
Bela Karolyi, the former gymnastics coach whose wife, Martha, coaches the US women's team, has repeatedly accused the Chinese of fielding underage female gymnasts. The ages of two other team members have also aroused suspicion: Jiang Yuyuan and Yang Yilin. Time magazine reported that government records, that have since disappeared, showed both girls to be 14. Gymnasts must be 16 to compete.
The minimum age for female gymnasts was increased from 14 to 15 in 1981, and up to 16 in 1997, to protect the physical and mental health of young athletes.
Nadia Comaneci was 14 when she won her fist Olympic gold medal in 1976. Yet despite her stardom, there were criticisms that young girls were being pushed too hard at an age when their bodies and bones were still growing, causing permanent damage. Ironically her coach was Mr Karolyi.
Not to worry, say US experts. The science of determining age is has been honed by decades of treating patients with growth disorders, identifying youthful homicide victims and determining the deportation status of illegal immigrants.
"It would be relatively easy," said Dr. David Senn, a forensic odontologist at the University of Texas Health Sciences Center who has analyzed numerous X-rays of immigrants apprehended at the border.
The science is based on measuring the growth of bones and teeth as children mature. Decades of data have been distilled into detailed tables recording the precise size and shape of skeletal components broken down by age, sex and race.
The task is so straightforward that Dr. Peter Hampl, president of the American Board of Forensic Odontology, said the Chinese government should just consent to X-rays and let the films speak for themselves.
"If there is nothing to be afraid of, let their kids be X-rayed," he said. "It's almost incriminating if they don't."
Dr. Gil Brogdon, a professor emeritus of radiology at the University of South Alabama, points out
Bones fuse together according to a well-documented schedule. For girls between the ages of 13 and 17, the best places to look are the knee, wrist, elbow and iliac crest on the pelvis, he said. The younger they are, the more obvious the evidence.
"A Caucasian girl is going to fuse her knee centers at about age 15; they're going to fuse their iliac crest at about age 16; and part of the elbow will start fusing around 13 or 14," he said. "That's the way you do it."
For the Chinese gymnasts, investigators would have to consult growth tables for Asian girls, Brogdon said.
One complication with teenage girls is that strenuous exercise can suppress estrogen production, delaying bone development and making them appear to belong to a younger person, said Dr. Vicente Gilsanz, a professor of radiology and pediatrics.
But Brogdon said that by comparing multiple bones, "you could come pretty close" to distinguishing a 14-year-old from a 16-year-old.
Teeth are also useful. U.S. immigration authorities often rely on dental X-rays to determine for deportation purposes whether an illegal immigrant is an adult or a minor.
"Of course, everybody who gets arrested says they are 17," Senn said.
He said he can pinpoint ages within 18 months using images of a person's wisdom teeth, which start forming around age 9 and are not fully developed until around 19. For the Chinese gymnasts, Senn said, he would also look at their second molars, which grow until age 15 or so.
Dr. Michael Baden, chief forensic pathologist for the New York State Police, said that with both teeth and skeletal X-rays, "you should be able to get within 12 months" of someone's age.
All this science probably won't mean much because Chinese authorities are not likely to agree to let independent doctors take X-rays of their gymnasts.
In that case, sports fans will be left to contemplate the girls' physical appearance.
"I must say, they do look kind of young," Baden told Karen Kaplan and Alan Zarembo of Los Angeles Times.