On Tue, 16 Nov 1999 09:28:30 -0800, Arthur V. Chadwick wrote:
>I love this. The period when all of the biochemistry of modern organisms
>was worked out is now pushed back into the remote abysses of the "blank
>period" (read "black box") of earth history, when there is neither a
>mechanism, nor any evidence for the evolution of anything. This is not
>faith, this is blind faith.
>
>
>"Earth-Science Reviews, 47(1-2): 71-93
>The origin of life
>J.H. McClendon
>105 Bush Street, Ashland, OR, USA
[...]
Thanks to Art for this abstract. This full text of this article is currently
available as a 991 kb *.pdf file from:
http://www.elsevier.com/cas/tree/store/earth/sub/1999/47/1-2/1084.pdf
The article is 23 pages long and it is an excellent overview. Elsevier's free
offer of this article on the Web ends 31 December 1999.
McClendon is saying that science will probably never know how life began
on Earth because: 1. the record of that time has been permanently
obliterated; 2. origin of life simulation experiments have come to an
impasse; and 3. the molecular search for a last common ancestor is doomed
because there is too long a distance between modern organism and the last
common ancestor and the last common ancestor and the origin of life.
IMHO when this finally sinks in, the cultural implications of this will be
immense. The general public looks to evolutionary science to provide its
naturalistic creation myth. As Phil points out:
"Biological evolution is just one major part of a grand naturalistic project,
which seeks to explain the origin of everything from the Big Bang to the
present without allowing any role to a Creator. If Darwinists are to keep
the Creator out of the picture, they have to provide a naturalistic
explanation for the origin of life." (Johnson P.E., "Darwin on Trial", 1993,
p103)
If the scientific materialists cannot tell people how we began, then they
might start thinking seriously about that other alternative...!
To help give more of the flavour of the article, below is the conclusion.
Steve
===========================================================================
11. Conclusions
The geological history of the Earth is in a mature phase as regards the early
Archean and Hadean. The biological fossil record goes back as far as we
can reasonably expect it. Perhaps, new discoveries will extend the record
into the Hadean, but that seems unlikely. Unfortunately, this history
apparently begins with metabolically advanced organisms which emit
elemental oxygen. Thus, much of the origin of life is still hidden from us.
Perhaps, exploration of Mars will give us more clues.
Likewise, the history of the formation of the solar system, and of the Earth
in particular, seems to be pretty well settled. But the atmosphere and
climate of the early Earth are not so well known and we need more
information about the composition of short period comets and the
deposition of organics on the early Earth.
There seems to be agreement that the water of the ocean came as comets.
Theoretical models indicate that the ocean arose within a few million years
of the origin of the Earth, accumulating after the massive impact that
formed the moon. At the same time, plate tectonics began, with submarine
hot springs and subduction zones. Since almost the whole lithospheric
surface was ocean floor, evidence of Hadean events has been destroyed.
The original atmosphere probably contained much carbon dioxide, to
generate the warming needed. On the other hand, perhaps the ocean was
kept warm only by incoming bolides. The geochemical evidence indicates
that the atmosphere was generally reducing or neutral until the Proterozoic.
Microfossil and isotopic evidence has been interpreted to indicate that
oxygen was being produced by Cyanobacteria as early as 3.8 Ga. This
apparently was used up in the ocean by oxidizing iron and sulfur, without
addition to the atmosphere.
Numerous possible sources of abiogenic organic compounds have been
identified. Some were extraterrestrial (meteorites, comets, smaller debris).
Others were terrestrial (impacts by meteorites in the atmosphere, lightning,
submarine hot springs).
The synthetic organic chemistry of 'prebiotic' compounds has come to an
impasse. Although many monomers have been shown to occur in
simulations, nucleic acid-type polymers resist our efforts. Proteins of
regular structure are likewise missing. Most of this work has involved
chemistry in solution, attempting to simulate primordial conditions. But
other approaches may yet yield fruit, such as the clay genes of Cairns-
Smith (1982, 1985) and the primitive autotrophs of Wachtershauser
(1994). Catalysis on mineral surfaces may be needed to provide the
stereospecific environment for biopolymer synthesis.
The projection backward of family trees has been very informative,
suggesting that the 'last common ancestor' was somewhere between the
Eubacteria and the Archaea. New is the suggestion that the origin of the
Eukarya (which share some characters with the Archaea) is between two
sections of the Archaea. Since modern thermophilic bacteria (both Archaea
and Eubacteria) occur near the root of the phylogenetic tree, some authors
suggest that the last common ancestor was a thermophile. But there is a
long distance between any modern organism and the last common ancestor,
and another long distance between the origin of life and the last common
ancestor.
Attempts to fill the gap between the remote origin and the last common
ancestor have been made. The `RNA world' is a term given to the idea that
the first 'genetic system was based on RNA rather than DNA.
But more than that, RNA is seen as the first enzymes, 'ribozymes', which
acted upon themselves to make new copies. There is some experimental
support for this idea, but limited. Nevertheless, the gap between simple
monomers and RNA remains.
Other approaches have to do with deciphering the metabolic pathways of
small molecule synthesis, to ascertain the order in which various systems
became available. It seems incontrovertible that the synthesis of amino
acids must have been devised early, as the supply in the environment ran
out. Lysine, being one of the rarest of amino acids that was needed, must
have had an early synthesis. Its synthetic pathway in most organisms is
unique; in the higher fungi its synthesis branches off the common citric acid
cycle. Consequently, it seems probable that the common pathway of lysine
synthesis preceded the invention of the citric acid cycle. Other syntheses
are not so clear, but the citric acid cycle, even today, is used for synthesis
of amino acids, and not for respiration, in some bacteria. An effort to unify
the development of metabolism is called for.
[...]
(McClendon J.H., "The origin of life", Earth-Science Reviews, Vol. 47,
Issue 1-2, 1 July 1999, 71-93, 88-89)
===========================================================================
Steve
--------------------------------------------------------------------
"Since we hardly know anything about the major types of organization,
suggestions, and suggestions only, can be made. How can one confidently
assert that one mechanism rather than another was at the origin of the
creation of the plans of organization, if one relies entirely upon imagination
to find a solution? Our ignorance is so great that we dare not even assign
with any accuracy an ancestral stock to the phyla Protozoa, Arthropoda,
Mollusca, and Vertebrata. The lack of concrete evidence relative to the
"heyday" of evolution seriously impairs any transformist theory. In any
case, a shadow is cast over the genesis of the fundamental structural plans
and we are unable to eliminate it." (Grasse P.-P., "Evolution of Living
Organisms: Evidence for a New Theory of Transformation", Academic
Press: New York NY, 1977, p17)
Stephen E. Jones | sejones@iinet.net.au | http://www.iinet.net.au/~sejones
--------------------------------------------------------------------