French woman Jeanne Calment, who died at the age of 122, and is considered the oldest person ever to have lived, may be a fraud.
Russian mathematician Nikolay Zak and gerontologist Valeri Novosselov say that Ms Calment's daughter, Yvonne Calment, assumed her mother's identity decades earlier, perhaps to avoid paying inheritance tax on the family's wealth.
In a paper for the Moscow Center For Continuous Mathematical Education published recently, Mr Zak cites discrepancies between the colour of Jeanne Calment's eyes, her height, and the shape of her forehead in a copy of a 1930s identity card and in her appearance later in life.
Among other arguments, Mr Zak claims that if Ms Calment was in fact 122 years old, she would have been much shorter, due to the rate at which a person shrinks as they age.
She married a distant wealthy cousin and outlived her daughter Yvonne, who died of pneumonia in the early 1930s according to official documents, her husband, and a grandson, before passing away in Arles, southern France, on 4 August 1997, earning her place in the Guinness Book of Record.
Jean-Marie Robine, one of two French scientists who validated Ms Calment's age, told France Inter radio the stir caused by the Russians' findings was a "ridiculous controversy".
The second, gerontologist Michel Allard, rejected the Russians' conclusions over her physical appearance in later life.