Jeanne Calment died in 1997 in the southern French town in which she was born, and her death drew a flurry of attention.

At 122, an age that had been certified by the Guinness World Records as well as public health researchers, she was the oldest documented person to have lived.

But a Russian mathematician is casting doubt on her record.

Nikolay Zak said in a report that he believes Calment was actually Yvonne Calment, Jeanne's daughter, who Zak says assumed her mother's identity to avoid inheritance taxes in the 1930s. If true, Yvonne Calment would've been 99 if she died in 1997.

The evidence produced by Zak in a paper published recently on the portal ResearchGate is not definitive.

He points to studies that show Calment had lost less than an inch of her height by the time she was older than 100, significantly less height loss than what would have been expected; Yvonne was taller than Jeanne, he says.

A passport for Jeanne in the 1930s lists different eye colors for her than she had later in life.

He also raises questions about other physical discrepancies in her forehead and chin. He also claims Calment had destroyed photographs and other family documents when she had been requested to send them to the archives in Arles.

The study has caused a global stir since it was issued. It has been covered by news media organizations around the world. Sample headline: "Jeanne Calment cheater?" France Inter radio asked.

But it has been denounced by some scientists, including Jean-Marie Robine, who validated Calment's age and wrote a book about her around the time of her death.

"All of this is incredibly shaky and rests on nothing," Robine told Le Parisien.

According to Smithsonian magazine, Robine said Calment answered questions when he interviewed her that only she would have been able to answer, like the name of her math teacher and housekeepers in her building.

"Her daughter couldn't have known that," he said, adding that town of Arles would have been in on the ruse.

"Can you imagine how many people would have lied? Overnight, Fernand Calment [Jeanne's husband] would have passed his daughter for his wife and everyone would have kept silent?" Robine said. "It is staggering."

Michel Vauzelle, who was the mayor of Arles when Calment died, has said the Russian's theory is "completely impossible and ridiculous."

Nicolas Brouard, research director at France's National Institute of Demographic Studies, said some in the research community favor "exhuming the bodies of Jeanne and Yvonne Calment" because of Zak's study, according to French public radio broadcaster RFI. He also said DNA testing could settle the debate.

In an email, Zak told The Washington Post that he became convinced Calment's age was suspicious in February while studying mortality patterns of people older then 105.

He said he started to investigate her life in September.

"I funded the work myself, it was a fascinating detective story in front of me," he said. "Those who criticize my work heavily are those who have a huge conflict of interest or those who didn't read it."

He called critics of his report "dishonest" and released a document that rebuts their rebuttals point by point.

Still, he admitted to Reuters that he does not have "cast-iron proof."

"I reviewed the whole situation," he said. "There are lots of small pieces of evidence."

Guinness World Records said it was aware of the report.

"Extensive research is performed for every oldest person record title we verify, which is led by experts in the gerontology field, and they have been notified of the current situation," it said in a statement distributed by spokeswoman Rachel Gluck.

Robine did not respond to a request for comment.

A Washington Post story about Calment's 120th birthday describes the broad contours of her life. She was born in Arles, in the south of France, on Feb. 21, 1875, before the invention of the lightbulb. She married Fernand Calment at 21.

"She dabbled in painting, played the piano in her parlor, rode her bicycle around town, hiked and hunted," buoyed by the success of her husband's fabric shop, reporter Dana Thomas wrote.

She said she met Vincent van Gogh as a teacher when he came to Arles to paint in 1888, saying she found him "very ugly, ungracious, impolite, sick."

"Pardon me, but we called him 'the madman.'" she said. She outlived much of her family. Yvonne died at 36 of pleurisy, Thomas wrote. Fernand died in 1942 at the age of 72 from eating tainted cherries. Calment's only grandchild, Frederic, was killed in a car accident at 36 in 1963.

Questions about age-related records are not uncommon. Shigechiyo Izumi of Japan was dubbed the world's oldest man when he died in 1986 at what was believed to be 120 years old.

But research that came out later claimed he was around 105. Others claiming ages as high as 125 and up have lacked the required documentation to prove their ages.

The secrets of an exceptionally long life remain elusive. Obituaries about Calment noted that she was known for her love of chocolate - she reportedly ate two pounds a week - treated her skin with olive oil and rode a bicycle until she was 100.

She had quit her two-cigarettes-a-day habit only a few years before her death - not for health, but because she could not longer light a cigarette without asking for help, The Washington Post wrote.

Under an obscure French system called viager - when a buyer purchases a home from an older person and begins paying mortgage but is only able to move in after that person dies - Calment had a man paying her mortgage for more than 30 years, The Post reported. She had signed the deal with him when she was 90.

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