RE: Parfit's token and type

From: Stathis Papaioannou <stathispapaioannou.domain.name.hidden>
Date: Sun, 8 Oct 2006 11:52:49 +1000

Russell Standish writes:

> On Sun, Oct 08, 2006 at 12:35:44AM +1000, Stathis Papaioannou wrote:
> > This is
> > literally true, given that from moment to moment, even in the absence of teleportation
> > etc., the atoms in your body turn over such that after a certain time none of the
> > matter in your body is the "same", and before this time the fact that some of the
> > matter in your body is the "same" is accidental and makes no difference to your
> > conscious experience.
> >
>
> We _really_ need to dispell this myth. It turns out that A bomb tests
> prior to the partial test ban treaty provides a unique clock that
> allows one to measure when a particular cell was born. It turns out
> that whilst this statement is true of various organs (eg the gut in
> particular), neurons turn out to have an average age just two years
> less than the age of the person (as measured in cadavers), ie most are
> born during the rapid brain expansion that occurs during the first two
> years of life.
>
> This is crucial, because I would suspect that neurons have far more
> relevance to one's person, than do gut cells.
>
> I posted on this before - it was reported in a recent New Scientist. I
> can dig out the reference if people are interested.

I'd be interested in the reference. However, I wasn't referring to turnover of cells, but
to turnover of components of cells. Water and electrolytes are freely and continuously
turned over while proteins and other structural components are continuously breaking
down and being replaced. I'm not sure of the numbers but I would guess that only a tiny
percentage of the matter in a neuron would be the same years later. If there are trillions
of radioactive atoms to begin with then by chance some of them will persist in a particular
cell provided it does not die. What is actually preserved in a neuron which survives over
the course of a person's life is a rough template and physical continuity, not the matter it
is comprised of. But for a few lucky atoms, ordinary living is equivalent to destructive
teleportation.

Stathis Papaiaonnou
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Received on Sat Oct 07 2006 - 21:53:10 PDT

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