From: toms@ncifcrf.gov (Tom Schneider)
Newsgroups: bionet.biology.computational
Subject: Re: Are viruses alive?
Date: 28 Jul 92 00:48:21 GMT
Distribution: bionet
Organization: Frederick Cancer Research and Development Center
Originator: biocomp@lerkim.umiacs.umd.edu


In article <1992Jul23.232327.17524@ctr.columbia.edu>
shenkin@avogadro.barnard.columbia.edu (Peter S. Shenkin) writes:

|In article <3605@fcs280s.ncifcrf.gov> toms@ncifcrf.gov (Tom Schneider) writes:
|>
|>In article <CMM.0.90.2.711650592.pkarp@Rockaway.AI.SRI.COM> pkarp@ai.sri.com
|>(Peter Karp) writes:
|>
|>|Harold Morowitz' forthcoming book, "Metabolism Recapitulates
|>|Biogenesis: The Beginnings of Cellular Life" has a succinct definition
|>|of living systems.  To paraphrase from a draft of the book, an
|>|autonomous biological self-replicating system is a molecular
|>|self-replicating entity that is capable of evolving, and that operates
|>|in the absence of other self-replicating entities.  Therefore, a virus
|>|is not an autonomous biological self-replicating system because it
|>|requires the presence of other self-replicating entities to replicate.
|>|Whether it is alive or not depends on whether you equate life with an
|>|autonomous biological self-replicating system, or simply a biological
|>|self-replicating system.
|>
|>Hmm.  So humans must not be "autonomous biological self-replicating systems"
|>because we depend on oxygen, vitamin C and various amino acids.  
|
|Morawitz specifies that live things cannot depend on other *self-replicating*
|entitities.  "Oxygen, vitamin C and various amino acids" are not 
|self-replicating, so they don't count.

I think they do because they are all made by other organisms (for the most
part).  And if humans make them by some process, then they still were made by
other organisms.

Unless humans aren't alive, in which case that doesn't make sense!

Hmm.  let "=>" mean "implies that".

Humans alive => plants on space station which depend on them are not alive

Humans not alive => plants on space station which depend on them are alive

plants not alive => humans on station that eat them are alive

plants alive => humans on station that eat them are not alive

So to have consistancy, we have two possible cases:

Humans alive => plants on space station which depend on them are not alive
plants not alive => humans on station that eat them are alive

OR

Humans not alive => plants on space station which depend on them are alive
plants alive => humans on station that eat them are not alive

But not both.  (The logic isn't that tight, but it does show how
the whole issue is pretty crazy.)

| The real reason we're not alive
|is that we eat plants and animals.

Ahhh yes, I suppose you are right.

|>   .... But I think
|>that most people would claim to be alive (or object violently if someone else
|>claimed that they were not!)....
|
|Now, now.... just because we claim to be alive, or object violently if
|someone else claims we're not, doesn't mean we really ARE alive....  :-)

Hmm.  I suppose that a robot which squacked when one turned it off would
be another example.  Then there is the case of the Moose program on a Mac,
which speaks witty things every 10 seconds.  I you turn it off it says
"Oh no!  Don't do that!"  There is a real problem here ... :-)

Thanks for helping me to muddy these waters...

  Tom Schneider
  National Cancer Institute
  Laboratory of Mathematical Biology
  Frederick, Maryland  21702-1201
  toms@ncifcrf.gov

Ps:  Have you heard the one about Dan Quayle and Mr. Potatohead
and who claims to be alive?

(We realize there must be a good joke starting with that sentence but haven't
finished figuring out the joke.  If you figure it out first feel free to post
it!)