Re: Logic Gives But One Choice On OOL. Can any find another?
- From: Tom Hendricks <tom-hendricks@xxxxxxx>
- Date: Fri, 7 Mar 2008 13:36:27 -0500 (EST)
On Mar 6, 11:56 am, Guy A Hoelzer <hoel...@xxxxxxx> wrote:
in article fqo5ra$6m...@xxxxxxxxxxxxxxxxxxx, Tom Hendricks at
tom-hendri...@xxxxxxx wrote on 3/5/08 11:18 PM:
On Mar 3, 12:22 pm, Guy A Hoelzer <hoel...@xxxxxxx> wrote:
in article fqeu0n$156...@xxxxxxxxxxxxxxxxxxx, Tom Hendricks at
tom-hendri...@xxxxxxx wrote on 3/2/08 11:09 AM:
On Feb 28, 12:49 pm, verulam <johnhewit...@xxxxxxxxx> wrote:
Tom,
OK, you feel the nucleotide problem can be solved but I do not agree.
I think nucleotides can only arise as part of an established
metabolism, which is a "metabolism first" viewpoint.
"Metabolism first' is a fluke chemical event. Now when metabolism pops up is
it immediately adapted to the environment, or is it destroyed in that
environment? if not adapted immediately, we need another fluke. That's two,
-
you'll need about 10 more before your'e done. And one is enough to rule out
life.
Tom,
I would count myself in the metabolism-first camp, and I think you are
missing the point of this view. The emergence of a metabolism de novo is no
more of a fluke event than the emergence of a convection cell in the
atmosphere. You could argue that a convection cell is initially spawned by
a fluke puff of wind that entrains the emergence of a full blown dissipative
structure, but that would also miss the point. Like a convection cell, a
metabolism does thermodynamic work. The structure of a dissipative
metabolism is fueled by local gradients (e.g., macromolecular structures,
thermal gradients, and so on) and could be sparked by chaotic chemical
dynamics (analogous to a puff of wind sparking a convection cell). I
wouldn't call chemical dynamics a metabolisms until positive feedback loops
are established, which effectively sustain the structure of the metabolic
chemistry (again, analogous to positive feedback within a convection cell).
'"Sparked" by chaotic chemical dynamics'? That sounds like a fluke to
me.
I don't think so, because the underlying chaotic chemical dynamics are
omnipresent. The source of the "spark" may not be predictable, but the
input of "sparks" is both predictable and abundant. The "sparks" are still
happening constantly today, although there is not enough fuel left to catch
fire (new origins of life), because it is already being tapped by the
biosphere. It is also possible that the biosphere has reshaped local
(earthly) material constraints in such a way that new origins have been
suppressed. At least this paragraph aims to explain my personal view a
little further, and why I don't see this model as requiring a fluke.
And why would metabolism be important? Do chemicals want to eat?
No, but thermodynamics "wants" to dissipate gradients. This can be
accomplished by favoring the emergence of dynamical, dissipative
autocatalytic sets of chemicals (a metabolism), which do "eat".
I'm looking at my table. Does my salt want to eat and my pepper want
to replicate?
Do chemicals want to get to you - to metabolism, to replication?
I think you are trying to get to whatever your definition of what life
is, and you are starting
it out with some special out-of-the ordinary events - fluke events.
I hope my responses above convince you that these points are not relevant.
Fluke events would only lead to life processes if they were not fluke
events
but often-happening events. Then they would be events that fit that
environment
and happened often in that environment, and were stable in that
environment.
The metabolic pathways would have to become stable, but the constant
sparking of chaotic chemical dynamics would be and could be far from stable.
IF what you suggest happened often and was ordinary, then
it may have had a part. If it was rare, then it was a fluke.
OK.
And overall remember if water is involved - and it is necessary to
life - all of this is a response to the
sun temperature cycle that keeps the water in liquid form. Can anyone
invision a scenario without
water?
It does seem that water has special properties that facilitate life but I,
for one, remain open to the possibility that our limited imaginings about
alternatives leaves open the possibility of life without water.
So no matter the chemistry it is all
a response to the environmental forces of the sun/uv/heat cycle. That
is where we should
be looking, not at metabolism, replication, or any of the other OOL
fluke scenarios.
I think you are being too defensive about the importance of your cycles.
Personally, I think the existence of cycles facilitates the de novo origins
of metabolisms, because they can make it easier to connect the extremes of a
gradient with channeled flows.
Guy
Temperature cycles are vital. Let's look at the earth without them.
No temperature cycle, and it either
gets continually warmer, gets continually colder, stays the same with
no variation.
Correct so far?
Always warmer - all chemicals burn up , and no chemical system
survives intact.
Always colder - all chemicals freeze and shut down chemical activity.
Always same with no variation - no variation means no alternatives to
choose from.
You may accept the sun cycle as a given, then suggest that sparks were
a subset that did
all the work. I think they contributed some, but it took the world
wide sun cycle
to force all the 'life' processes into being.
Life apes the sun cycle in every cell - there's constancy from the
past, and variation that evolves.
.
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