"Hmmm.... I guess it would have been a good idea to state my own views
before playing the role of the skeptic so that people don't get the wrong
idea."
Probably not a bad idea. Since I don't know you very well, and since you
seemed to be rather adamant in your claims, I assumed you were a creationist
arguing against any form of abiogenesis. I apologize for jumping to
conclusions, but on this list you don't always know who your adversary is.
"No No. His claim was that it is not certain that they existed."
Well, again, having assumed you were a creationist, I thus assumed that your
quotation of that excerpt was meant to imply that Miller was attacking the
idea of a primeval reducing atmosphere. Since I doubted that would be the
case, I had to assume that was your opinion.
"Actually, I admire Miller a great deal because of his willingness to admit
to the possible weaknesses of his own theory and even to perform and publish
experiments that would, to some, seem to falsify his own theory."
I admire him for that, too, but creationists are known to take ruthless
advantage of such honesty to misconstrue it into anti-evolutionary claims.
"For this reason I am very skeptical of your suggestion that Miller was
being critical of Fox out of competitiveness."
Well, I was trying to counter what I thought was your use of Miller (an
authority figure) to disprove Fox's work. I may be wrong, but scientists
are competitors, and Miller and Fox are promoting their own models as the
sole explanations for abiogenesis, so it seemed reasonable to attribute his
statements to competitiveness.
"In context, what Miller means by 'considerable opinion' is reasonable,
informed, scientific opinion of experts in the field."
Again, creationists tend to use "considerable opinion" as if it were a
substitute for physical evidence. I thought that's how you meant it.
"IOW, the results you present from Mason would also be 'opinion' in the way
Miller is using the term."
I would disagree. Mason is reporting on what we could claim to know based
on actual physical evidence; he wasn't speculating based on the evidence.
"I'm going to omit the Mason quote for sake of space. Let's see what we can
agree on. Can we agree that hard evidence ends 3.8 billion years ago with
the Isua rocks of Greenland?
No. As Mason points out, we have hard evidence in the form of meteorites
that, when heated, give off the right gases in the right proportions to make
a reducing atmosphere.
"Can we agree that at this latest point of hard evidence that the earth's
atmosphere was most likely neutral or mildly reducing?"
Yes, that evidence seems rather clear.
"The rest seems to me to be speculation."
The rest of what? Mason? He supports everything with evidence. My
summary? I base it on Mason. I don't see any speculation here.
"Now, just as there is more than one type of 'opinion' there is also more
than one type of speculation. So, I'm not talking here about wild
speculations but reasonable speculations based upon reasonable models etc."
But its not speculation if it is supported by evidence, as Mason's
information is.
"Now, my major 'complaint' here involves exaggerated optimism."
I would hardly call it "exaggerated" if you have evidence to support your
optimism.
"Our knowledge is much too rudimentary for such brash optimism, IMHO."
I disagree. I think Mason's data, plus Miller's, plus Fox's, is enough to
create a testable working theory. That's all I need to be optimistic.
"If one wants to say that its possible that the earth's atmosphere prior to
3.8 billion years ago may have been reducing...."
But Mason's data establishes that the atmosphere between 4.5 and 4 billion
years ago was reducing.
"...and that perhaps enough organics formed in the atmosphere or came from
comets etc. to make a soup etc. etc. then I will readily concede that its
possible."
Again, Miller's data establishes that this was most likely, given that a
reducing atmosphere did exist.
>
"This sounds very much like what Miller wrote in the paper I cited. I opted
for the results at low H2/CO2 ratios because every study I looked at said
that H2 was present in trace amounts if at all. Mason is the first author
I've seen suggesting that there may have been large amounts of H2. If there
was, then I would concede that things look much better for soup theory."
This only applies, though, to conditions of a neutral atmosphere. In a
reducing atmosphere methane alone would set the ratio at 4. So before the
switch to a neutral atmosphere at approximately 4 billion years ago, there
would have been enough hydrogen present in both methane and ammonia to
satisfy the requirements of a Miller-Urey experiment. On top of that,
hydrogen can also be made by the photodestruction of water and the
photoxidation of iron.
"I'm kind of curious how anyone would think that Miller would write a paper
critical of abiogenesis :). It never occurred to me that I would need to
write a qualifier for that! :) For the record, none of the studies I cited
were critical of abiogenesis. Some authors may be critical of a particular
*theory* of abiogenesis but it seems that all the papers I have regarding
the possible neutrality of the earth's early atmosphere take abiogenesis to
be a fact."
Again, thinking you were a creationist I believed that you were using these
papers to try to prove abiogenesis was impossible. I appreciate you taking
the time to explain your position more carefully. Next time I promise to
treat your opinions with more respect.
"I really think you need to expand your horizons a little."
I would suggest the same for you.
Kevin L. O'Brien