>PM>Why not ? Please explain why these amino acids would change their
>>left handedness ?
>SJ>The burden of proof is on those who claim it. The facts are:
PM>And those who claim it, mentioned how left-handedness could have
started.
Stephen : <<It has been well-known for some time that L- (or R-) handedness can be
generated by polarised radiation or light:>>
But now the source of this light might have been identified which could explain the observations.
And certainly it was not brought up in the manner described above. These were limited to radiation on earth.
<<"Preferential interaction with radiation. A number of researchers have
pursued the idea that certain types of radiation are able to destroy one of a
pair of enaniomers. This preferential destruction could lead to an
accumulation of one enantiomer in the primeval soup. Circularly polarized
sunlight, for example, leads to a selective photochemical decomposition of
chiral molecules. The effect is rather weak and it is doubtful whether it
could have affected the composition of a primeval soup." (Croft L.R.,
"How Life Began," 1988, p62)
"Suggestions have been made over the years that circularly polarised light
may direct the synthesis of optically active compounds; that one optical
isomer may spontaneously crystallise from a racemic mixture, or be
selectively absorbed on asymmetric crystals; and that L and D monomers of
amino acids may exert some stereoselective action during peptide bond
formations. Most of these suggestions, and others of a similar kind, have
not been confirmed experimentally." (Aw S.E., "Chemical Evolution," 1982, p99)>>
Again irrelevant.
<<But this finding did not even do that, despite all the hype. What they found
was circularly polarised *infrared* light, which is too weak to selectively
destroy R- or L- amino acids to generate homochirality:
"A team led by Jeremy Bailey of the Anglo-Australian Observatory near
Sydney has spotted circularly polarized INFRARED LIGHT-in which the
electromagnetic wave rotates steadily-streaming from a region of intense
star birth in the Orion Nebula. ULTRAVIOLET (UV) LIGHT polarized
this way can selectively destroy either lefts or right-handed (D) amino
acids, depending on the direction of spin...INFRARED LIGHT, however,
DOES NOT PACK THE ENERGY NEEDED TO DESTROY ORGANIC
MOLECULES. THAT WOULD TAKE UV LIGHT." (Irion R., "Did Twisty
Starlight Set Stage for Life?" Science, Vol. 281, 31 July 1998, pp626-627.
My emphasis.)>>
So infrared might not have worked but ultraviolet might ? What is the big deal here ?
PM>Why would the amino acids revert to an even-handed distribution ?
The summary article points this out:
Stephen : <<"Origin-of-life experts have a different spin. "There are so many problems"
with the scenario, says biogeochemist Jeffrey Bada of The Scripps
Institution of Oceanography in La Jolla, California.), who doubts that large
quantities of amino acids from space would have survived the journey to
Earth or hung around long enough to influence early biology. "I doubt this
will settle the issue of how homochirality arose." (Irion R., "Did Twisty
Starlight Set Stage for Life?" Science, Vol. 281, 31 July 1998, p627)>>>
A personal opinion: "Who doubts that"... Not very useful an argument dear Stephen
Stephen : <<
"Once the amino acids get to Earth THEY WOULD RACEMIZE IN
VERY SHORT ORDER,' Miller says." (Irion R., "Did Twisty Starlight Set
Stage for Life?" Science, Vol. 281, 31 July 1998, p626. My emphasis.) >>
Again a personal opinion. But is this truely the case ? How did the meteorite survive if it woulde racemize in very short order ?
>SJ>1. No extra-terrestrial non-racemic (ie pure L- or R-handed ) amino
>acids have ever been found. There has been claims of 90% L-amino acids
>found but these were non-biological amino acids.>>
PM>No one is talking about pure L or R handed amino acids.
Stephen : <<But "pure L or R handed amino acids" are the *only* ones that work,
because a protein will not fold if even *one* wrong optical isomer is present:
"Furthermore, the activity is destroyed by the incorporation of one
analogue or one wrong optical isomer because that prevents the folding of
the protein chain." (Yockey H.P., "Information Theory and Molecular
Biology," 1992, p254) >>
Which assumes that no activity will take place but if there are twice as many L than R, there will be some that do work.
>SJ>2. All terestrial amino acids that are not part of a living organism are
>racemic (ie. a mixture of L- and R- handed).>>
PM>Hence the hypothesized origin among the stars.
Stephen : <<Yes. But there is no evidence that those are not racemic also.>>
We disagree. The meteorite appeared to show differently. We have observation as well as hypothesis. Time will show.
>PM>You must surely aware of some of the excellent work which has
>shown that such is hardly as far fetched as you sound it to be. Fox and
>others have gone through many of the steps required.
>SJ>Please give *details* with *references*. If you are referring to
>Sidney's Fox's so-called "proteinoids" theory, origin-of-life specialist
>Robert Shapiro observed that Fox's it has the unique distinction of being
>criticised for its lack of "relevance" by both evolutionists and
>creationists:
PM>Irrelevant you are now arguing from authority not from fact.
Stephen : <<It is superficial and fallacious to dismiss a reference as "arguing from
authority not from fact." Both laymen and all scientists outside their own
field of expertise, *must* rely on the "authority" of other scientists who are
experts in their respective fields:>>
If that is the case you surely agree that there is no evidence of Intelligent Design ? Or is this a limited argument ? Sidney Fox and others do believe that there is relevance to his data. In fact we can just look at the data and ignore the opinions of others to determine the relevance ?
PM>What is much harder is dealing with the findings of Fox
Stephen : <<First, how do you *know*, since you are an oceanographer? You *must*
be relying on the *authority* of "Fox" or someone else relying on "Fox".>>
Or on the findings by Fox and others ?
Stephen : <<Second, unless you post exactly what are "the findings of Fox", with
references (as previously requested), you are here using your *authority*
as an argument that "much harder is dealing with the findings of Fox".>>
Finally we are dealing with some direct information "Science and Creationism ed. Ashley Montagu" p 194 "Creationism and evolutionary proto biogenesis".
>SJ>The fact is that a million people in Western Australian read on the
>front page of their major newspaper that doubt was thrown on Darwin's
>origin of life theory. I doubt that the layman would know the difference
>between Darwin's origin of life theory and his evolution theory. That's
>why I said it was "ironic".
PM>You are presuming that the average Australian would see this as
'doubt of Darwin's origin of life theory'. And even more, that this would
affect how they perceive Darwin's evolution of life theory.
Stephen : <<Yes. That's what I said.>>
You surely hold some low opinion of Australians. Not all have the poor education, US students enjoy in biological highschool sciences. But then again, in science personal opinion does count little.
>SJ>BTW I am not aware of any evidence that "smokers" even existed 3.5
>billion years ago when life first appears in the rocks. Another article I
>posted pointed out that the oldest "smokers" on Earth are only 27,000
>years old and they are only active for 2,000 years at a time.>>
PM>Yep, some volcanoes of the past have since long gone dormant,
>haven't they.
Stephen : <<Yes. "Volcanoes" can lie "dormant" and then come to `life' again. But the
problem for living things depending on smokers, is that if the smokers went
dormant every "2,000 years" then that life would die, unless it could
migrate to another "smoker". If it could migrate to something other than a
smoker then the smoker theory is superfluous.>>
So you agree that your present day data says little about how it might have been billions of years ago ?
Stephen : <<For the smokers theory to be viable, its proponents would have to show: 1)
that smokers existed "3.5 billion years ago when life first appears in the
rocks"; 2) there has been a unbroken series of contiguous smokers for the
last "3.5 billion years"; and 3) that those life forms can migrate to other
smokers.>>
Even without such evidence, the hypothesis remains viable, unless you can show that no such continuous series exists. You are using some poor science to use present day situations to predict past behavior. Extrapolation far beyond the capabilities of the data. Where have we seen that before ?