6 PHOTOS Clues in oldest woman's blood See Gallery Blood from world's oldest woman suggests life limit OSAKA, JAPAN - MARCH 05: Misao Okawa, the world's oldest Japanese woman eats her birthday cake on her 116th birthday celebration at Kurenai Nursing Home on March 5, 2014 in Osaka, Japan. Okawa, born in Tenma, Osaka, on March 5, 1898 to a family of Kimono merchants, married in 1919 and had three children, of which a daughter and a son are still alive, and has four grandchildren and six great-grandchildren. (Photo by Buddhika Weerasinghe/Getty Images) OSAKA, JAPAN - MARCH 05: Misao Okawa, the world's oldest Japanese woman eats her lunch ahead of her 116th birthday celebrations at Kurenai Nursing Home on March 5, 2014 in Osaka, Japan. Okawa, born in Tenma, Osaka, on March 5, 1898 to a family of Kimono merchants, married in 1919 and had three children, of which a daughter and a son are still alive, and has four grandchildren and six great-grandchildren. (Photo by Buddhika Weerasinghe/Getty Images) This picture taken on July 4, 2013 shows Fu Suqing (R) talking to a young lady in Shuangliu county, southwest China's Sichuan province. Fu, turned 116 year-old on July 19, received a bronze medal recently from Carry Flag World Records showing that she's the world's oldest living person, local media reported. CHINA OUT AFP PHOTO (Photo credit should read STR/AFP/Getty Images) Up Next See Gallery Discover More Like This HIDE CAPTION SHOW CAPTION of SEE ALL BACK TO SLIDE

It sounds kind of bizarre, but researchers say blood from one of the world's oldest women gives new clues about a human's "life limit."Before her death in 2005, Hendrikje van Andel-Schipper of the Netherlands was the oldest woman alive. She lived to be 115 and three months old.Surprisingly though, CNN reports that when she died, her brain was still in good shape - no sign of Alzheimer's or other diseases typically associated with old age.So what led to her death? Researchers now say it might have to do with dying stem cells.Scientists at VU University Medical Center in Amsterdam say at the time of van Andel-Schipper's death, she had just two blood stem cells.Let us put that in context for you. Blood stem cells are what your body uses to replenish your blood. Humans are typically born with around 20,000 of these cells, and on average about 1,000 work to keep your bloodstream pumping.But this study suggests over time our stem cells weaken and die out, which, as a writer for New Scientist points out, might actually limit the ability of your stem cells to replenish your tissues."Once the stem cells reach a state of exhaustion that imposes a limit on their own lifespan, they themselves gradually die out and steadily diminish the body's capacity to keep regenerating vital tissues and cells, such as blood."Although it's not known for sure whether van Andel-Schipper died because of this exhaustion, this study does reveal her white blood cells were mutated, leading scientists to wonder if some genetic mutations are actually harmless.And as the International Business Times says, it could mean: "Genetic mutations may hold the key to a long life."The researchers, whose findings were published in the journal Genome Research, say more studies are needed to investigate whether dying stem cells can cause death at extreme ages.