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what is alive?

Mario Vaneechoutte Mario.Vaneechoutte at rug.ac.be
Wed Sep 18 11:31:50 EST 1996


> Mario.Vaneechoutte wrote:
> >>
> 
> >A nice one.
> >However, 'bad' and 'good' always depend on the point of view you take.
> >For individual organisms, viruses surely are bad news. But, evolution
> >and evolution towards more complex organisms owes a lot to viruses.
> >Humans usually consider 'evolution towards more complex organisms' as
> >good (otherwise we wouldn't have been here).
> 
JohnJoe McFadden wrote:
Many people do not see increasing complexity as 'good'. See eg. SJ
Gould's many excellent books including his latest (which I haven't yet
read) which argues strongly against the 'complexity=good' viewpoint.
Anyway, viruses are surely genetically-selfish elements that are in
there for their own 'good', not that of the host. Any role they may have
had in evolution (and I am not aware of any strong case where this has
been demonstrated) is purel;y accidental.

My reply:
I agree. I didn't claim that I make the analogy 'complex = good'. I
tried to say that is a valid analogy for many people.
More in general, I tried to say that 'good' is a very subjective term,
not useful in biology.

However, with respect to the role of viruses, I think to have understood
that their role in shaping genomes is very important. Also important
shifts in population genetics may be attributed to viral infections.
Think of the recent epidemic in Scandinavian seals whereby three quarter
of the population was eradicated. One can easily imagine that only
certain of the major histocompatiblity complex'(comparable to HLA in
humans) types have survived and thus that the genetic make-up of the
population has been altered (that the species has been changed?)

Think of HIV: very recent information has shown that certain mutants of
chemokine receptor CCR5 provide resistance towards infection (Samson et
al. 1996. Nature 382: 722). Even if HIV would infect the whole world
population there would be noninfecable survivors, all with a certain
genetic characteristic.
(Infection in general alters the genetic composition of populations)

JohnJoe McFadden wrote
> Sure, replication is neccessary for the procreation of life but is it >what defines life? No mule has ever replicated but I don't doubt that a >mule is alive. No definition of life is perfect but merely replicating >information is too broad - it could also bring in cultural stuff such as >those irritating chain mail letters and e-mail's that also replicate >themselves within the right environment (ie. a gullible reader). Life is >a lot more wonderful 

'Wonderful' isn't useful either. Again very anthropocentric.

that a computer virus or a chain mail letter - not just more
> complex - it differs at more fundemental levels.

My reply:
I still don't see problems for calling this living information. As a
consensus, we can use 'life' only when we refer to biological living
information.


> 
Mario Vaneechoutte
Laboratory Bacteriology & Virology
Blok A, De Pintelaan 185
University Hospital Ghent
Belgium 9000 Ghent
Tel: +32 9 240 36 92
Fax: +32 9 240 36 59
E-mail: Mario.Vaneechoutte at rug.ac.be



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