With age comes wisdom teeth

This New Scientist article, usually accessible only to subscribers, is made available for free by the Museum of Applied Arts and Sciences in Sydney, Australia

GUESSING someone’s age can be risky at cocktail parties, but what about when their future is at stake? For refugees, the difference between childhood and adulthood can be the difference between asylum, deportation or jail.


Thanks to international child protection laws, asylum-seekers are more likely to be admitted to wealthy nations if they are under 18. Minors get access to many social programmes and as such they can be costly to governments, so officials want to be confident on the age issue. When documents are in question – or do not exist – immigration departments look to science.

Unfortunately, attempts to assess age with X-ray scans of teeth or wrists are doomed to failure, according to work to be published this week in the British Medical Bulletin. The fundamental flaw with such tests is that, because children grow at widely different rates, skeletal maturity shown on X-rays – which is used to gauge age – doesn’t necessarily match chronological age. Teenagers can have adult bone structure as early as 15 or later than 20, says study author Tim Cole at University College London (UCL). He says X-rays can provide the wrong answer about whether someone is under or over 18 up to a third of the time.

“It’s superficially an easy question to ask, but answering it is fraught with difficulties,” says Al Aynsley-Green, an emeritus professor of child health at UCL, who led the study.

“It is superficially an easy question to ask, but answering it is fraught with difficulties”

Dental scans are also used to determine the maturity of wisdom teeth. These can reach full maturity as early as age 15, as late as 25, or in some cases never fully develop at all.

In wrist scans, age is estimated by looking at 20 or so bones initially separated by cartilage, but which progressively move closer to one another until they fuse in the mature wrist. The reference used for this test is a 1959 atlas compiled for doctors to assess healthy bone development, not age. It includes 1000 X-ray images of wrists of white middle-class American children, and the fully mature wrist of a 19-year-old. Yet wrists can be fully mature in children as young as 15, says Cole. A rival atlas compiled a few years later indicates a mean chronological age for wrist maturity of 17.6 years – give or take 1.3 years. So most “children” have “adult” wrists before 18.

The use of age-determination tests is currently at issue both in the UK – where the UK Border Agency is contemplating a trial of the wrist technique – and in Australia, following incidents including a 2010 scandal in which three Indonesian child immigrants were illegally jailed as “adults” after wrist X-ray tests. They were released last year after providing birth certificates, but about 60 immigrants that arrived with them are currently in jail while their claims of age are checked. The Australian Human Rights Commission is holding an inquiry into the practice.

Still, faced with large numbers of immigrants from poorer countries, immigration officials in richer nations have increasingly been turning to X-rays as a “scientific” way to resolve age disputes. A 2010 study of 22 European countries found that 16 conduct bone scans and 10 use dental X-rays. The US has used both tests for almost two decades.

Practitioners of the dental technique in the US have defended it, saying the inability of such tests to give exact ages has long been known and accepted. “The trick is to know its limitations. We’re estimating age, not determining it,” says Jim Lewis, chairman of the Age Estimation Committee of the American Board of Forensic Odontology. Lewis says that the “wisdom teeth” technique was developed in 1993 and has been used since then by the US immigration services without controversy.

Outside of immigration services, sports governing bodies have an interest in ensuring athletes compete in appropriate age bands. Yet both the International Olympic Committee and the international football federation, FIFA, have agreed not to use X-rays to resolve age issues.

What technique would be more effective? Aynsley-Green and his team say that the best hope is in detailed assessments of physical and psychological development by specially trained paediatricians, skilled in combining different aspects of growth to make an informed estimate of age. It is crucial to chart a new way forward, he says: “Governments must stop believing that there is a ‘scientific’ test that will tell precisely the age of individuals claiming to be children but without papers to prove it.”