DNAunion@aol.com writes
in message <b1.282ba59.273073bc@aol.com>:
>
> DNAunion: By saying this, are you suggesting that the individual
> components of a bacterium used to be capable of living independently,
> but once incorporated into bacteria, they lost that ability?
> For example, were ribosomes once free-living entities, and at
> that ancient time, ;bacteria; did not have ribosomes (but later
> acquired them through symbiosis)?
Yes, with the caveat that such a free-living entity would not
be "just" a ribosome but a ribosome plus something else.
Likewise, these hypothetical ancient bacteria, would not be
"just" bacteria without ribosomes, but cells functioning
with something else. (My excuse for so many hypotheticals would
be that science hasn't yet ruled out the chemical possibility
of replicators simpler than bacteria.)
Of possible relevance, I just noticed this abstract on PubMed
"Early evolution: prokaryotes, the new kids on the block." which
argues that the ribosome had a prior function before protein
synthesis (
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10497339&dopt=Abstract).
> >>>Thadley: Thus, breaking a bacterium down into individual components
> > > would accomplish the same result as breaking a bacterium
> down into individual molecules, or individual atoms. Nothing in
> the short term.
>
> DNAunion: Or in the long term.
Perhaps it would, given trillions of exploded bateria in trillions
of environments. However, that is not the mechanism I'm proposing
for abiogenesis since the age of the universe seems to rule it
out.
<snip>
> DNAunion: Symbiosis is a method by which *preexisting* life
> becomes more complex. I would still like for you to *clearly*
> state how you are proposing symbiosis assisted the origin of
> the very first cells.
What is needed first is several plausible replicators of any
kind. Then, some degree of divergent evolution followed by
competition among strains. I can't give you a step by step
scenario, though, but I don't think its nonexistence is
obvious.
> DNAunion: Points 1 & 2 taken together -- there truly IS SOMETHING
> that can arrange matter in complex and organized ways, and (2)
> there truly IS NOTHING that opposes matter's being arranged in
> organized and complex ways -- indicate that all natural reactions
> would lead irreversibly toward greater complexity and organization.
Oh, I see. Let me backtrack and reject (2), since there are clearly
many processes that "unarrange" matter.
> > >Thadley: In this [prebiotic] case, the pools would result
> > >in far simpler "life" than bacteria, and possibly, over time
> many different kinds of simple "life" as molded by environmental
> pressures. This simpler life, then, would make those "macro"-leaps
> of complexity with something similar to symbiosis.
>
> DNAunion: What type of simpler life are you referring to?
> There is no simpler autonomous cellular life than the simplest
> autonomous bacterium.
Extinction due to competition with more successful life forms
seems plausible.
> As far as the simpler-than-bacteria
> self-replicators, they are still only designed; none have been
> shown to arise under prebiotically plausible conditions (and
> many leaders in OOL research express grave doubts that ever will
> - at least RNA replicases).
What are the latest obstacles? It might depend on who you read.
At the very least, there is a great deal of molecular data that
certainly hints at some sort of complex chemical history, whether
the ultimate location of that is terrestrial or not.
http://imbs.massey.ac.nz/Research/MolEvol/Farside/ANT_RES.HTM
> And even if a self-replicator arose, how would symbiosis of
> preexisting simple life forms explain the use of ribosomes by
> all cells, since ribosomes are neither free-living nor living
> at all, and no material I have read proposes that they ever
> were?
I'm using living and replicating in the same way.
<snip some questions -- possible answers may be alluded to above,
but to the rest I can't offer any but the most speculative answers>
> DNAunion: A little off the subject, but somewhat related.
> Margulis has stated to the effect (and I agree) that it is a
> bigger leap going from amino acids to a bacterium than it is
> going from a bacterium to a human: that is, prebiotic chemical
> evolution is more difficult than subsequent biological evolution
> (the real quote can be found at www.pansermia.org, but I
> don't know exactly where at that site it is). If the
> smaller, easier leap (for the first cells to evolve into humans)
> took about 4 billion years, then wouldn't the larger,
> harder leap (for prebiotic chemical evolution to produce the
> first cells) take much longer than 4 billion years? Yet the
> maximum windows now being discussed are on th e order of 200
> million years, with the average hovering around 50 million, with
> some even less.
I see the origin of life as sort of a black box with us having
the occasional barest glimpses into its interior. Processes we
can observe will always be seem to be easier to understand than
processes we can only guess at, so I'm not sure I'd agree with
with the implication that amino acids to bacteria is really a
qualitatively larger leap. Maybe quantitatively, yes.
Let me ask this. Do you think we should stop researching
naturalistic methods of the origin of life? Do we know enough
now about the origins of life to conclude it didn't happen
naturalistically 4 billions years ago on Earth?
This archive was generated by hypermail 2b29 : Fri Nov 03 2000 - 16:04:35 EST