_A reader inquires: I read that the world’s oldest woman won’t get the record because she doesn’t have a birth certificate. Isn’t there a way to figure out how old a person is based on her biology?

Any fan of CSI knows the power of bioforensic tests. Police regularly establish a suspect’s presence at the crime scene using DNA from blood or semen. Individuals send away their cheek-swabbed cell samples to learn about their genealogical history.

But these tests rely on deciphering genetic codes, and for the most part, we understand genetic codes. Aging, well, that’s a little more opaque. There are no biological tests that can determine with any accuracy one’s age. According to Steven Austad,
author of Why We Age, “if the person is extremely elderly, over 75 or 80, it’s very difficult for anyone to estimate better than within, say, 20 to 25 years, how old they are.”

It’s not that aging doesn’t leave a variety of biological clues. Over the years, lung capacity tends to decrease, eyesight and hearing worsen, skin loses its elasticity, and telomeres, the DNA caps at the ends of chromosomes, shorten as a result of many cycles of cell division. But although these dreaded indicators show up in almost everyone sooner or later, they don’t seem to happen at a set time. A countless number of factors influence the aging process, most notably one’s
genetic history, socioeconomic status and personal habits. Until we better understand the intricacies of aging, there will be no algorithm, no deterministic way for a doctor to enter a
set of facts and a blood test into a computer and have it spit out an age. Life, to put it simply, is too complex.

The lack of a test to establish a person’s age has led to frequent controversies. Before Bruna Rumbo passed away last December in Parlier, California, her family claimed she was born in 1887, making her 116 years old.

According to Guinness World Records, this would have made her the world’s oldest living person.

But Guinness only considers candidates who possess birth certificates, census reports or other documentation, which Rumbo did not have. Hence the award went to 114-year-
old Charlotte Benkner of North Lima, Ohio, who as we went to press still holds the title. And while Austad can never know for sure how old Rumbo really was, he keeps in mind this
simple maxim: “The No. 1 cause of extreme longevity,” he says, “is not knowing when you were born.”