Steven B. Harris wrote:
For organisms with central nervous systems (essentially: brains),
> the division into separate individuals is more natural. Chang and Eng
> may stay connected as Siamese twins, but you still call them two
> individuals due to the two brains. Thus, brains introduce aging. It's
> liguistic. If you grew a new head every 100 years and the old one
> beside it then died, and otherwise you didn't age, would you be
> ageless? That would all depend on the survival of your memories.
> If they were somehow transfered to the new head, we'd say you were
> ageless (but had really bad dandruff). If not, we'd say you died and
> your body grew a new head, and a new person.
>> So now we see that "aging" as we talk about it here on this form, is
> not really a biological process, but one of definition of the
> individual, which is not really a biological entity in humans, but
> rather a more insubstantial being composed of information (software).
> "You" are not your cells, but rather your memories. The cells may be
> replaced, but if your memories stay intact, "you" survive. And by
> definition, do not "age" (though you may grow older).
>> Steve Harris, M.D.
Being that I am interested in ageing and possible life extension of somatic
cells, the preceding doesn't advance my understanding much. Philosophy,
unlike biology, IS mostly a question of semantics, but I am not interested
in that. Maybe you're being sarcastic. Most of the cells in aspens and
humans age, die, and do not reproduce themself indefinitely. Germ cells
(and some malignant cells too in vitro) reproduce themselves indefinitely,
and in aspens apparently so do the root cells. What would advance our
understanding are experiments to find out, for example, if the root cells
express telomerase and if the root cells have stable telomeres. Maybe this
is already known. Or if anything is different about the root chloroplasts
than the rest of the chloroplasts in other tissue?
BTW, do any plants have mitochondria in addition to chloroplasts?
