One-hundred-sixteen-year-old Maria Esther de Capovilla died on Sunday, less than a year after Guinness World Records had verified her birthday—Sept. 14, 1889—and named her the world's oldest living person. How'd they know how old she was?
They checked her records. To verify extreme longevity, Guinness works with the Gerontology Research Group, an organization that keeps an updated list of people who have lived past the age of 110. (These are called "supercentenarians." If you live past 100, you're a regular old "centenarian.") To get your name on the list, you have to provide an original birth certificate or baptismal certificate, along with corroborating marriage certificates and a photo ID. (The ID weeds out record-seeking impostors.)
Researchers who study the super old typically consult several independent sources before they grant centenarian status. Naturalization certificates can be especially misleading, as new immigrants may have boosted their age to qualify for work. Social Security benefits provide another incentive for age inflation. The self-reported data in the U.S. census are suspect for the same reasons. Studies of the data from 1980 found as many false centenarians as real ones. A similar examination in the late 1990s found that 16 percent of the 100-pluses had the wrong birth dates listed in the census.
If they can't find a clean birth certificate or other records, the researchers might try a "family reconstitution." They'll gather as much information as they can on the person's children, siblings, and parents and then compare everyone's ages and birth orders to make sure they're consistent. If someone turns out to be only 10 years younger than her mother or 40 years older than her sister, they know there's a problem.
What about biological tests for age? There aren't any. You won't find any reliable age markers in humans, such as the rings on a tree stump or the inner ear bone of a fish. Some gerontologists have tried to measure age by testing a wide range of age-related characteristics—including hearing loss, cataract formation, immune response, and joint flexibility. In theory, you might be able to use these measures to figure out how far along someone has gone in the aging process. At best, this would give you a measure of "physiological age" but not the number of calendar years a person has lived.
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