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From: Susser.pasa@Xerox.ARPA
Newsgroups: net.sf-lovers
Subject: Re: Matter transmission and duplication (#366)
Message-ID: <3699@topaz.RUTGERS.EDU>
Date: Thu, 19-Sep-85 16:41:26 EDT
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Posted: Thu Sep 19 16:41:26 1985
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From: Josh Susser 

>From: Keith F. Lynch 
>  A duplicate isn't satisfactory?  Don't you know that the average
>atom in the body only stays there a few weeks?  Only a small
>percentage of the you of a year ago still exists.

I remember when my 9th grade biology teacher told me this.  It seems to
be a common belief among high-school science teachers.  But look at it
this way:  if "the average atom in the body only stays there a few
weeks" (let "a few weeks" = a fortnight), then one would have to replace
half his body mass twice a month, with most of the replacement mass
coming from food.  For a person of average mass, say 80 kg, this would
require eating and ABSORBING 20 kg of food a week!  While eating 20 kg a
week (about 5 lbs a day) isn't unreasonable, absorbing that many
molecules is ridiculous.  Most of what we absorb from food is glucose,
vitamins, some amino acids, a few nucleotides, and water.  The rest of
what we eat is roughage.  So I really can't believe that a human could
eat enough to replace an appreciable proportion of its body mass even in
a few months.  I'm sure there is some amount of turnover in some of the
more active structures (muscles, bone marrow, skin, blood), but I can't
believe that the atoms in my brain cells or in my DNA molecules are that
volatile.

Any molecular biologists out there care to tell me what I'm made of?

-- Josh Susser 

"Even the Devil needs an advocate now and then."