What about with an autopsy? Is there any way to determine someone's age postmortem?
You can open up a centenarian's brain and you'll see some areas that look like that of a 50-year-old or of a 110-year-old. You can have variation in the basic process of aging, called senescence, in different parts of the same body. You can look at someone's teeth after they die to evaluate their age, but I'm not sure if Dosova has any.
What are some other signs that help indicate someone's age?
Older people usually have dementia, which is cognitive decline due to aging, of one form or another. When they tested Jeanne they thought she had dementia, because she was very quiet, but it turned out she just spoke an obscure dialect of French. She was remarkably intelligent and alert and could remember things way back in her life. She remembered meeting Vincent van Gogh in southern France, for example, and remembered songs from early childhood. Later in life, she was largely blind, deaf and bedridden—the things that went wrong with her just happen to most of us at a younger age. But she did ride a bicycle until she was 100.