Re: Paper: Life: In search of the simplest cell
From: Anthony Cerrato (tcerrato_at_optonline.net)
Date: 02/09/05
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Date: Wed, 9 Feb 2005 11:42:32 -0500 (EST)
"TomHendricks474" <tomhendricks474@cs.com> wrote in message
news:cuc7sa$uf$1@darwin.ediacara.org...
> << True. It seems to me that for _long term stability_
those
> "organisms," i.e., "proto-organisms"/cells/etc. etc.,
would
> require added insulation from the ever-changing
> environmental (physical and chemical) disruptions which
may
> obtain. Cell (or primitive proto-cell/membrane) walls
> provide added "buffering" from such ever changing factors,
> at least until some sort of refined metabolism is
developed
> to handle such problems to some degree. More simply, there
> are local and (near-)global islands of stability which
have
> to be considered over geologic
> time periods.
> Without such stability, how can replication of
> any kind become possible?- >>
>
>
> Tom:
> But you are missing the obvious IMO. And that is
replication IS what makes it
> stable in that environment. Metabolism IS what makes it
stable in that
> environment. Cell membrane IS what makes it stable in that
environment.
> All these life attributes are life because they were most
stable in that
> environment in the first place.
Where did I say they weren't? But I was not trying to define
a time sequence for the attributes in the appearance of
"life," I was just pointing out that, without the added
"buffering/insulation" provided by proto-cell-walls, the
specific forms which obtained might not have had the
long-term global stability [fitness] to long survive. In
actuality, all three--proto-cell membranes,
proto-replication, and proto-metabolism, all co-evolved at
roughly the same time...when the dust settled, the fittest
forms survived [without radical form changes] over longer
periods and over a wider range of varying physico-chemical
environments. Clearly, by definition, life didn't occur
until proto(minimally)-replication appeared, but stability
of forms required all of the three properties noted.
> The cart doesn't come before the horse.
Depends what you define as cart and horse in the specific
analogy to life. It gets rather semantically muddy as to at
what point you call a system true "metabolism,"
"replication," or "cell-wall." What comprises each of these
at the "proto-" stages is not well-defined, and the early
versions of all of them were not invariant systems but still
in a state of flux, evolving together.
> These life attributes didn't pop and then 'adapt', they
pop and were stable and
> because of that stability = life.
Yes, by definition life is a system/form which exhibits
stable manifestations (taking account of successor progeny.)
But at some point, the stability attributes of the first
proto-life-form _did_ in fact just "pop" before their
replication based stability was demonstrated. That's what
the first O in OOL means. :)
> Life is that which survived and produced novel variants in
a 'sun/heat cycle -
> and some of the novel varianst were replication,
metabolism, cell division,
> etc.
Yes, I think it's pretty obvious that life requires energy
and the ability to utilize it, and that it will evolve
variants that best capitalize on these by optimizing all of
its attributes.
Cheers, ...tonyC
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