My hypothesis is that it's just the continuation of the development program that starts with conception. It just turns self-destructive at some point, because natural selection didn't do anything about that because when humans were living in caves, no one lived to these kinds of ages anyway.
So, to rejuvenate the body, you would have to find where the current state of that program is stored, and overwrite it to a younger one, as if using a debugger. So far there are two promising developments about that: Michael Levin's research about bioelectricity, and Harold Katcher's research about exosomes (he seems to have abandoned it, but other people are picking up).
So, to rejuvenate the body, you would have to find where the current state of that program is stored, and overwrite it to a younger one, as if using a debugger. So far there are two promising developments about that: Michael Levin's research about bioelectricity, and Harold Katcher's research about exosomes (he seems to have abandoned it, but other people are picking up).