Q: If I am 95 years old, do I have any cells in my body that were present when I was 3 years old? What about at conception? Also, could you expand on your earlier statement, “stem cells live a lifetime?” In a nutshell, I am curious if I am a completely “new” person or if there is anything “in” me that has been with me since birth…or conception.Jonathan, Los Angeles, California, USA
A: Nope, we’re not completely new people. In fact, most of our cells are a good seven-to-ten years old, as biologist Jonas Frisén, professor at the Karolinska Institute in Stockholm, reported in July 2005. For example, we grow a new skeleton over about a 10-year period.
Moreover, at 95 we will have three kinds of cells we’ve had since three years of age and, indeed, since before birth. They last a lifetime:
• cerebral cortex neurons
• heart muscle cells
• cells in the inner portion of the crystalline lens of our eyes.
“I wouldn’t necessarily single out cerebral cortex neurons as lasting a lifetime because it’s probably true that most neurons in the entire adult brain were generated during development,” e-mails neuroscientist Elizabeth Gould professor of psychology at Princeton. more>>>
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