Read Nick Lane. He makes a good argument for a metabolism first
abiogenesis. He observes that the ADP<->ATP energy cycle is the same in
every organism and he shows how it could have originated in alkaline
ocean vents.
Brent
On 7/6/2019 5:09 PM, John Clark wrote:
On Sat, Jul 6, 2019 at 6:34 PM Lawrence Crowell
<goldenfieldquaterni...@gmail.com
<mailto:goldenfieldquaterni...@gmail.com>> wrote:
/> The idea of the RNA world runs into trouble with the ribosome,
which is a hugely complex system of RNA and proteins/
In the RNA world there would be nothing nearly as large and competent
as modern ribosomes and there would be no proteins at all, there would
just be short single strands of RNA floating in a sea of nucleotides.
As far as I know nobody has yet found a RNA string that could catalyze
the duplication of a string of nucleotides as large as itself, but
they have found a RNA string called tC19Z that could reliably copy,
without the help of proteins, RNA sequences 95 nucleotides long. And
that is almost half as long as tC19Z itself. I find that encouraging.
Ribozyme-Catalyzed Transcription of an Active Ribozyme
<https://science.sciencemag.org/content/332/6026/209>
John K Clark
RNA sequences up to 95 letters
no be anything as big as a ribosome or any proteins at all, there
would be short single strands of RNA floating in a sea of nucleotides
neucteatides
On Saturday, July 6, 2019 at 5:04:40 PM UTC-5, John Clark wrote:
On Sat, Jul 6, 2019 at 4:18 PM Lawrence Crowell
<goldenfield...@gmail.com> wrote
> We have lots of hypotheses on this, but it is a point
where biological evolution loses explanatory power, just
as general relativity fails at the center of black hole
collapse.
I think that's the key point, Darwinian Evolution can't take
over until you have a replicator of some sort, in fact I would
say the origin of heredity is the same thing as the origin of
life. That first replicator was certainly far simpler than
anything alive today and it almost certainly didn't have any
DNA in it. RNA is only single stranded not double as DNA is
and it is usually much shorter too, and RNA would help in
getting over the chicken or the egg problem. RNA can carry
information, not as well as DNA can but it can do it. And RNA
can act like an enzyme and catalyze chemical reactions, not as
well as proteins can but it can do it.So the first RNA life
would be very incompetent by modern standards but with Darwin
you don't have to be perfect you just have to be better than
the competition.
In 1986 Nobel Laureate Walter Gilbert said in the journal Nature:
"/One can contemplate an RNA world, containing only RNA
molecules that serve to catalyze the synthesis of themselves.
The first step of evolution proceeds then by RNA molecules
performing the catalytic activities necessary to assemble
themselves from a nucleotide soup/."
However some people, like Chemist Graham Cairns-Smith think
that even the RNA world, although far simpler than modern
life, was still too complicated to be the first replicator aka
the first life. Cairns-Smith proposed that the very first
replicators were not organic at all but were clays were
information was encoded in a pattern of defects in silicate
crystals. In 1985 he wrote a book about it that is now online:
Seven clues to the origin of life
<https://www.krusch.com/books/evolution/Seven_Clues_Origin_Life.pdf>
The problem with figuring out how life started is that
chemicals usually don't have fossils, so even evolutionary
biologist and militant atheist Richard Dawkins admits that
although he likes the Cairns-Smith theory we may never be able
to say this is definitely how life started and it couldn't
have started any other way, the best we can do is find a
plausible way that life *could* have started.
John K Clark
The complexity group at Santa Fe Institute has a 3 month course on
the origins of life. I thought about joining, but decided not
because my plate is already a bit full and frankly all we really
have to go with are hypotheses. The idea of the RNA world runs
into trouble with the ribosome, which is a hugely complex system
of RNA and proteins. How that got going is difficult to know.
I had this idea about RNA interactions with carbon nanofibers.
Could RNA coil up around these and these could serve as some
system for translation? Maybe in time this became more complex
with more RNA and proteins bound to the system. Eventually this
evolved into the ribosome. I looked this up and found of course
other had taken up this idea.
LC
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