[...]
BH:===
>"I must admit that I was somewhat taken aback by Kevin's statement that the
>Miller Urey experiment was an example of abiogenesis."
>
KO:===
>Biologists and biochemists define abiogenesis as the formation biological
>material from non-biological material using non-biological processes. The
>Miller-Urey experiment made biological materials from non-biological
>materials using non-biological processes. Seems to match the definition to
>me.
>
BH:===
>"This is due to the fact that I had always seen the term used as Burgy is
>using it."
>
KO:===
>No offense, but you're not a biologist or a biochemist, so you wouldn't know
>what the current definition was.
>
Apparently you are unaware that the same word is often
defined differently in different fields. If you want to
see how the word abiogenesis is used wrt the origin of
life, you can run over to the t.o archives and take a
look at the abiogenesis FAQ written by Andrew Ellington
(the infamous deaddog), a fairly well know researcher in
the origin of life field.
Ellington also wrote an excellent piece for t.o several
years ago entiltled: <Origins of life: A redefinition>
Since this is apparently not in the t.o archives I will
post it to this group. I'll do this in a separate posting
since I believe it to be of general interest. For purposes
of our discussion here I would invite you to look at how
he uses the term abiogenesis. In particular his statement:
"Evolution is a fact. Abiogenesis is not." Now, if the
Miller-Urey experiment is an example of abiogenesis as
used in the origin of life community then abiogenesis is
obviously a fact, wouldn't you agree?
[...]
BH:==
>"In any event, Burgy makes a good point. In defining abiogenesis as Kevin
>has one divorces abiogenesis from necessarily having anything to do with the
>origin of life on earth."
>
KO:==
>Since life is based on metabolism, which is based on biomolecules, I don't
>see how defining abiogenesis properly divorces it from "necessarily having
>anything to do with the origin of life on earth". Unless of course you
>believe that life cannot be explained inmaterialistic terms alone.
>
>If "life" is not metabolism based on biomolecules, then please define
>"life".
>
Note the word necessarily. More on this below.
BH:===
>"For example, if 'the origin of life on earth' occurred at a deep sea
>hydrothermal vent, then the abiogenetic production of amino acids by passing
>electrical discharges through a reducing atmosphere probably had nothing to
>do with 'the origin of life on earth'."
>
KO:===
>Interesting you should bring that up. I recently read an article by Miller
>in which he stated that the major problem with the hydrothermal vent model
>was that there were no proposed mechanisms by which a vent could make
>biomolecules, but lots of known mechanisms by which a vent could break them
>down. I'm not using Miller's statement as "proof" that this model is false,
>but it does seem to me that that is a very serious problem. That may be why
>many abiogeneticists are returning to the reducing atmosphere idea, but
>throwing in the added idea of prebiotic material concentration followed by
>solid-phase catalysis. Sounds alot like some of Fox's original ideas.
>
Apparently, Fox does not agree:
"The chemistry of the lunar source comports with prominent
components of intersteller matter, formaldehyde and ammonia
(Fox and Dose, 1977), and is thus more plausible than the
highly publicized production of amino acids in an atmosphere
by the action of lightning, a model regarded as using
geologically implausible conditions of hydrogen-rich atmosphere
and electric discharge in closed regions (Florkin, 1975)."
-- Sidney Fox, 1995.
Putting this aside, let me just say that I am very familiar
with the controversy surrounding Miller's experiment and
studied it closely several years ago. I would be interested
to learn your source in case there are some new developments
that I'm not aware of. I noticed that Shock (one of the
proponents of the hydrothermal vent scenario) recently published
some new results in <Science> (Amend and Shock, 1998) but
have not had a chance to look at it carefully yet. The list
of references shows that there have been a number of new
results since I last looked at all this. The only one of these
I had time to look at was a paper by Huber and Wachtershauser
(1998) which has apparently stirred up some interest.
But I'm digressing. Several criticisms of the hydrothermal
vent scenario occurred within a period of a few years from
some well respected researchers, for example Miller and Bada
(1988 and 1991), Gerald Joyce (1988) and E.G. Nisbet (1989).
Of these, Miller's caused the most stir, probably because
of his experiment. Not long after, several counters to
Miller and Bada appeared, those I know of are Shock (1990, 1992),
Holm (1992), Marshall (1994) and Fox (1995). Perhaps
most significant of these is Shock's (1990) criticism
of Miller's experiment.
So that's the state of the debate when I last looked at
it several years ago.
Well, this is very interesting, but also beside the
point I was trying to make. If you look through the
references below you will find examples of experiments
which qualify as abiogenesis according to your definition.
Let me turn the argument around from my previous statement.
If the origin of life occurred a la Miller, then most
perhaps all of these examples would not have anything to
do with the origin of life. This is why I said that
abiogenesis (as you've defined it) does not *necessarily*
have anything to do with the origin of life on earth.
======references======================================
Amend, J.P. and E.L. Shock, 1998. "Energetics of Amino
Acid Synthesis in Hydrothermal Ecosystems," <Science>
281:1659-1662.
Fox, Sydney W. 1995, "Thermal Synthesis of Amino Acids
and the Origin of Life"_Geochimica et Cosmochimica Acta_
59(6): 1213-1214.
Holm, Nils G. 1992, "Why are Hydrothermal Systems Proposed as
Plausible Environments for the Origin of Life?", _Origins
of Life and the Evolution of the Biosphere_, 22:5-14.
Huber, C. and G, Wachtershauser 1998. "Peptides by activation
of amino acids with CO on (Ni,Fe)S surfaces: Implications for
the origin of life," <Science> 281:670-672.
Joyce, G. 1988, "Hydrothermal Vents too Hot?", _Nature_, <334>:564.
Marshall, W.L. 1994, "Hydrothermal Synthesis of Amino Acids",
_Geochimica et Cosmochimica Acta_, <58>:2099-2106.
Miller, S.L. and J.L. Bada, 1988, "Submarine Hot Springs and the Origin
of Life," _Nature_, <334>:609.
Miller,S.L. and J.L. Bada, 1991, "The origin of life did not take place in
submarine hot springs," _Eos Trans. Amer. Geophys. Union_,
72(suppl.), p. 59.
Nisbet, E.G. 1989. "Origin of Life," _Nature_ 337:23.
Shock, E.L. 1990, "Geochemical Constraints on the Origin of Organic
Compounds in Hydrothermal Systems," _Origin of Life and Evolution
of the Biosphere_, <20>:331-367, 1990.
Shock, E.L. 1992, "Hydrothermal Organic Synthesis Experiments," _Origin
of Life and Evolution of the Biosphere_, <22>:135-146.
============================================================
Brian Harper
Associate Professor
Applied Mechanics
The Ohio State University
"He who establishes his arguments
by noise and command shows that
reason is weak" -- Montaigne