In other words, the metabolisms-first view envisions the
prior existence of a physical potential (e.g., a thermal
and/or macromolecular gradient) that pulled dynamic
metabolic (chemical) structures into existence. [...]

Guy wrote:

In other words, the metabolisms-first view envisions the
prior existence of a physical potential (e.g., a thermal
and/or macromolecular gradient) that pulled dynamic
metabolic (chemical) structures into existence. [...]

The metabolism-first vs genes-first terminology never
made much sense to me - since any living system would
need a both a metabolism and a heritable information
store.

Guy wrote:

In other words, the metabolisms-first view envisions the
prior existence of a physical potential (e.g., a thermal
and/or macromolecular gradient) that pulled dynamic
metabolic (chemical) structures into existence. [...]

The metabolism-first vs genes-first terminology never
made much sense to me - since any living system would
need a both a metabolism and a heritable information
store.

However, the concept above /does/ make sense. Comparing
with other self-organising systems, we find eddies become
more likely as shearing stress increases, spontaneous
crystal seeding becomes more likley as super-saturation
increases - and so on. However a mix of hydrogen and oxygen
tends not to spontaneously combust anywhere near room
temperature and pressure. Similarly with nuclear
chain reactions - they take quite a "push" to get
started in earth-like conditions. There /is/ still
a means to coax these dissipating systems into spontaneous
action by providing a suitable energy gradient - but it can
take a rather extreme set of circumstances to get things
going.

IMO, this is support for the idea of life as a dissipating
system which forms spontaneously when a sufficiently
intense energy gradient arises - since all other
self-organising systems seem to operate like that too.

However, you do not /have/ to squeeze hydrogen and oxygen
at increasing temperatures to set off a reaction. Even if
an increasingly intense energy gradient would /eventually/
lead to an explosion, that doesn't rule out the possibility
of an explosion being caused by a spark.

A clear issue here is whether life is easy to get started,
on prebiotic energy gradients, or if there is a big energy
barrier to overcome - and some need for an exceptional energy
push - from a lightning strike, or some such.

I think the lesson from other self organising systems is
that this is not obvious and could go either way. In other
words, other self organising systems themselves don't
provide much of a clue about how energetically easy it was
for life to start - except to say that it could require
either a little energy or lots of energy, or for that
matter either a rare spark or a commonplace chance event.

However, there may well be a clue from modern ecosystems.
They /don't/ need much of an energetic push to get going.
Seeds germinate without being struck by lightning - or
anything much more than some spring sunshine. Of course
we cannot assume the existence of seeds, but they are
an existence proof for the idea that living systems
need a particular configuration of matter - and not
necessarily a huge energy gradient.

There are plenty of other clues about how life started,
so the answer to this question will probably drop out
from an examination of them.

"Tim Tyler" <seemysig@cyberspace.org> wrote:
Guy wrote:

The metabolism-first vs genes-first terminology never
made much sense to me - since any living system would
need a both a metabolism and a heritable information
store.

The terminology makes sense to me. Many 'genes-first'
scenarios (especially Cairns-Smith, but also RNA-first)
contemplate an original metabolism which is so impoverished
as to hardly deserve to be called a metabolism. Heterotrophic
accumulation of 'building blocks' from the environment and
their assembly or condensation is not really 'metabolism' in
my view. To have 'metabolism', ISTM that you at least have
to make some of the 'building blocks' yourself, or at least
to activate the blocks with some kind of 'high energy bonds'.

Similarly, while I agree that some kind of heritable information
has to exist to have 'life', I wouldn't say that the information
has to be 'genetic' in the Schroedinger or Watson/Crick sense.
That is, the information does not need to involve information-bearing
molecules or 'alphabets'. It can be more subtle: topological, for
example; or based on whether particular autocatalytic cycles
are in the 'ignited' state. Any attractor of a dynamical system
is potentially a form of information inheritance which is not
'genetic' in the usual senses.

"Tim Tyler" <seemy...@cyberspace.org> wrote in messagenews:fqo5r9$6ks$1@darwin.ediacara.org...
Guy wrote:

In other words, the metabolisms-first view envisions the
prior existence of a physical potential (e.g., a thermal
and/or macromolecular gradient) that pulled dynamic
metabolic (chemical) structures into existence. [...]

The thrust here seems to be that something cannot be called
a 'fluke' if it is the inevitable result of deterministic thermodynamic
forces.  Of course, Tom believes his own scenarios are fluke-free
precisely because he sees them as the inevitable response to
environmental forces.  But I'm not sure this is the right way
to think about things.  There are at least three different senses
in which the word 'fluke' might be appropriate, even though
the result is inevitable given physical law.

The first sense is that the key event (such as the ignition of
an autocatalytic cycle due to the appearance of a cycle
constituent or such as the chance appearance of a self-replicating
polymer sequence) might inevitably happen sometime over a
period of (say) a million years.  But it still has to be called
a 'fluke', in some sense, when it actually does happen 600,000
years (say) after the clock started.

The second sense is that the key event might be inevitable
on some kinds of planets but practically impossible on most
planets.  So, the fact that our planet (or even any planet in
our galaxy) is appropriate for the origin of life might be called
a fluke.

And thirdly, notice that there are hundreds of thousands of
deterministic and inevitable chemical events in this universe
and that most of them have absolutely nothing to do with the
origin of life.  It may well be a 'fluke' that the laws of our
universe happen to be set up such that abiogenesis is inevitable.

Now, you can perhaps invoke the 'anthropic' principle to
make these 'flukish' events seem quite unsurprising.  Fine.
But if you do that, the word 'fluke' should hold no terrors.
There is then no particular philosophical reason to avoid
OOL stories that include 'flukes' or 'just-so-stories' in their
plot outline.

In my preferred OOL scenarios, the key events were
'flukes' in the first sense and possibly in the second and
third senses as well.  And I don't see any reason why
I should feel ashamed of this.


The metabolism-first vs genes-first terminology never
made much sense to me - since any living system would
need a both a metabolism and a heritable information
store.

The terminology makes sense to me.  Many 'genes-first'
scenarios (especially Cairns-Smith, but also RNA-first)
contemplate an original metabolism which is so impoverished
as to hardly deserve to be called a metabolism.  Heterotrophic
accumulation of 'building blocks' from the environment and
their assembly or condensation is not really 'metabolism' in
my view.  To have 'metabolism', ISTM that you at least have
to make some of the 'building blocks' yourself, or at least
to activate the blocks with some kind of 'high energy bonds'.

Similarly, while I agree that some kind of heritable information
has to exist to have 'life', I wouldn't say that the information
has to be 'genetic' in the Schroedinger or Watson/Crick sense.
That is, the information does not need to involve information-bearing
molecules or 'alphabets'.  It can be more subtle: topological, for
example; or based on whether particular autocatalytic cycles
are in the 'ignited' state.  Any attractor of a dynamical system
is potentially a form of information inheritance which is not
'genetic' in the usual senses.

I have no problem with topologies, and attractors being "genetic"
in principle - though of course there are practical problems about
whether such ideas are plausible OOL suggestions.

All modern life uses template copying, and it's far from obvious
that anything else will actually work -

e.g. see Genetic Takeover, page 74.

Anyway, if you define genes as being nucleic acids, or a
molecular-chain template replicator, or some such, then
the "metabolism-first" terminology would also make sense.

"Tim Tyler" <seemysig@cyberspace.org> wrote in message news:fqs1va$2gme$1@darwin.ediacara.org...

I have no problem with topologies, and attractors being "genetic"
in principle - though of course there are practical problems about
whether such ideas are plausible OOL suggestions.

All modern life uses template copying, and it's far from obvious
that anything else will actually work -

Or rather, all known modern life uses template copying for the
biggest part of the work of heritability. Many instances of
non-template-based heritability exist though - from the classical
cortical inheritance in cilliates to the phenomena of epigenetic
'imprinting' using mechanisms of (non-template) methylation
of the DNA.

And since these things actually DO work, you probably mean to
say that it is far from obvious that these kinds of things can work
*well enough* on their own without also having a template-based
genetic system in operation to do the 'heavy lifting'.

e.g. see Genetic Takeover, page 74.

So, is a minimal (that is, barely sufficient for 'life')
metabolism-oriented genome simpler than a minimal template
oriented genome. Clearly, it is. The minimal
metabolism-oriented genome is one bit! That bit
'encodes' (embodies?) one complete autocatalytic cycle.
But the minimal template-oriented genome must be much
larger than one bit. Much, much larger if it needs to
indirectly specify the copying machinery and the
anabolic pathways for the alphabet elements.

Anyway, if you define genes as being nucleic acids, or a
molecular-chain template replicator, or some such, then
the "metabolism-first" terminology would also make sense.

But that makes the Cairns-Smith idea a 'metabolism first'
scenario. I don't think that anyone wants that. [...]