A study by Russian researcher Nikolay Zak has disputed Jeanne Calment's claimed age with a hypothesis that Jeanne's daughter Yvonne, born 1898 and claimed to have died of pneumonia in 1934, usurped Jeanne's identity upon Jeanne's death in 1934. In that scenario, Jeanne Calment would have died already in 1934 and Yvonne Calment in 1997, claiming to be her mother and aged 122 but in fact she was aged 99. However, to prove if the hypothesis is true, a DNA/blood test is required.