>1) Glenn, in his analogy between a functional sentence and a functional
>protein, assumes the existance of letters (amino acids). In fact, in a true
>abiogenesis scenerio, the existance of amino acids are not a >given.Glenn's
post ignores the probability of generating the 20 amino >acids from their
component parts even though this must be included in >the total probability
of generating a functional protein from scratch. It is >not a trivial
exercise to form large concentrations of the 20 amino acids >using only the
starting materials and energy sources present upon the >early earth.
>
First I would like to thank Eddie for all the earlier agreement, but since
agreement is inherently boring, I will respond to the very good criticisms he
directs at these arguments.
I want to state that I do not think evolutionists have proven the abiogenesis
case yet, but I fear, for what I beleive are good reasons, that they will
eventually succeed in their efforts to create novel life forms by stochastic
(random) means. My personal opinion at the moment is that God created life
by fiat. But I am not at all opposed to the concept that God planned living
systems into the nature of DNA, RNA and Protein phase spaces. (a phase space
is the multidimensional space in which each position in a sequence is one
dimension. A 4 amino acid protein has a 4 dimensional phase space) Eddie is
correct that an estimate of the total probability must include the
probability of generating the amino acids from their components. (A point of
information, according to Yockey, Information Theory and Molecular Biology,
p. 199 says that 140 amino acids are found in modern proteins)
But I want to make clear that the probability argument applies to two issues
in the C/E debate. First, it does apply to the abiogenesis issue. If the
probabilities of finding a given function are too low, then abiogenesis is
impossible. But a less well known issue to which the argument also applies
is the evolution of novel proteins in living systems. Once again, if the
probability of finding a particular function is too low, then even natural
selection would be unable to find it. How low is too low?
There are 8760 hours in a year. Let us assume that the early earth is able
to make 1 million novel proteins each hour by stochastic means (whatever the
machine might be.) World-wide this might be a relatively slow rate.Thus in a
million years you have 10^16 selections. So in a million years you could
probably have created most functions which have a mapped probability of
10^-16. In a billion years you could find by random selection any function
which is performed by 10^-25 of the proteins.
Eddie wrote:
>2) In fact, each of the 20 amino acids has two enantiomers (optical
>isomers). The functionality of proteins depends upon their organization in
>3-D space. But in order to form the alpha helix and beta sheet >structures,
you need all (or a very large percentage) of one optical isomer. > However,
in any plausible abiogenesis scenerio, both enantiomers are >present in equal
quantities in the prebiotic soup. For the non-chemists in >the crowd,
enantiomers are mirror images of each other like your right >and left hands.
In Glenn's analogy, they would be backwards letters (see >below). Thus, in
Glenn's alphabet soup, there are 20 functional letters >and 20 backwards
letters and the inclusion of any backwards letter into a >sentence destroys
the functionality of the sentence. Needless to say, >this strongly decreases
the probability of a functional sentence.
>__ __
>__| |__
>__| |__
>
Agreed. My example does not include chirality. However, originally during
the earliest periods of the development of writing letters did have
chirality. Frank Moore Cross wrote:
"We now recognized clearly for the first time certain features of the two
styles of alphabetic writing. The Old Canaanite was multidirectional:
written horizontally from right to left, or from left to right, and
vertically. "~Frank M. Cross, "The Invention and Development of the
Alphabet," in Wayne M. Senner, editor, _The Origins of Writing_ (Lincoln:
University of Nebraska Press, 1989), p. 81-83
Why do we only have one form of letter chirality today? One form won out.
But beyond that, I will not venture. I am aware of the chirality problem for
the origin of life and it is indeed a tough one. One that may not be able to
be overcome. However, I will cite one fascinating datapoint which has
implications for the chirality argument. Amino acids extracted from Murchison
meteorite are not racemic but actually have a higher L concentration. (See
Engel, Macko and Silfer "Carbon Isotope Composition of Individual Amino
Acides in the Murchison Meteorite,", Nature 348, Nov. 1, 1990, p. 47-48. and
Engel and Nagy, "Distribution and Enantiomeric Composition of Amino Acids in
the Murchison Meteorite, " Nature, 296, April 29, 1982, p. 838) If these
amino acids, formed out in space somewhere, can be predominately left-handed,
then there must be a non-biological mechanism to produce such a
preponderance.
As to the flexibility for replacement changes I offer this.
I am knot sure thet surtain erors distroy the function of the sentance. All
the spelling errors in the last sentence were intentional (unless I made one
by mistake :-) ) Those errors did not destroy the functionality of the
sentence entirely. I bet you were able to understand the meaning. Thus
there is a certain amount of flexibility in sequences which do not entirely
destroy the functionality.
Eddie wrote:
>3) Glenn's shortest funtional sentence is eight letters, but there are no
>functional proteins of eight amino acids. I don't know what the length of
>the shortest functional protein is, but I'm guessing it would have to be at
>least an order of magnitude higher (80 AA).
Vasopressin has 8 amino acids. For the cow, it consists of
tyr-phe-glu-asp-cys-pro-arg-gly. It is a pituitary protein. See Isaac
Asimov, The Genetic Code, The New American LIbrary, 1962, p. 83
Vasopressin increases blood pressure and regulates kidney action (p. 82)
A change to the order tyr-iso-glu-asp-cys-pro-leu-gly produces oxytocin. It
causes the contraction of the smooth muscles and is the chemical they gave my
wife during the births of our 3 kids to induce labor.
Eddie wrote:
If generating a functional
>protein is as easy as Glenn's scenerio implies, all we would have to do is
>fill a bunch of vats up with amino acids in a mild aqueous solution, warm
>them up a bit and pull out all kinds of functional proteins. It is my
>understanding that people have been working on this kind of stuff since >the
1950's and it just isn't that simple.
>
This is exactly what is going on now in labs around the world. They call it
directed evolution. See the article the quote below comes from.
Andrew Ellington and Jack W. Szostak "used small organic dyes as the target.
They screened 10 13 random-sequence RNAs and found molecules that bound
tightly and specifically to each of the dyes.
"Recently they repeated this experiment using random-sequence DNAs and
arrived at an entirely different set of dye-binding molecules.
...
"That observation reveals an important truth about directed evolution
(and indeed, about evolution in general): the forms selected are not
necessarily the best answers to a problem in some ideal sense, only the best
answers to arise in the evolutionary history of a particular
macromolecule."~Gerald F. Joyce, "Directed Evolution," Scientific American,
Dec. 1992, p. 94-95.
>>"There was a post on Talk Origins by Ellington Feb. 19, I quote:
Bartel's recent experiments (1,2,3) with selecting ribozymes
suggest that RNA molecules that have catalytic activities
compatible with self-replication may be extremely common.
Bartel is currently attempting to convert one of his
ribozymes into a polymerase. If this conversion is
successful, it highlights the relative ease with which
life could have arisen given suitably activated
mononucleotides.
"However, we need not focus on RNA: any self-replicating
system is fair game. Along these lines, Luisi Luigi's
self-replicating liposomes (likely referenced in 4) have a
'probability' associated with their success that is near 1:
given the presence of esterified fatty acids and a basic
environment (which some authors have claimed for life's
origins), self-replication is unstoppable."<<
his references :
(1) Ekland et al., NAR, 23:3231 (1995).
(2) Ekland et al., Science, 269:364 (1995).
(3) Bartel et al., Science, 261:1411 (1993).
(4) Oberholtzer et al., BBRC, 207:250 (1995).
Eddie wrote:
>4) It may be true that under "just right" conditions that the spontaneous
>generation of a functional protein is inevitable if given some time and a
>decent amount of starting material. But were these conditions actually
>present upon the early earth? And, if so, why did the incredibly unusual
>circumstances perfect for the formation of life occur instead of the
>millions of other hostile scenerios? This doesn't destroy the probability
>argument, but simply moves it to a new arena. (The the probability of
>favorable initial starting conditions also appears to be very small.)
>
>I am not an expert in the whole area of probability and abiogenesis. But I
>don't think the issue is as simple as either Duane Gish or Glenn Morton's
>scenerio suggest. In my opinion, a good solid reference that is skeptical
>of abiogenesis but is sensitive to the complexity of the issues involved is
>Thaxton C.B., Bradley W.L. & Olsen R.L., "The Mystery of Life's Origin:
>Reassessing Current Theories". They did a much better job of stating the
>difficulties of abiogenesis than I can.
I agree that the abiogenesis issue is not simple. And I certainly have not
solved it (and never will). But that does not give us the right to use
sloppy arguments.
I have a real problem with one of the arguments in Thaxton, Bradley and
Olsen. On page 138 they calculate the entropy for the 4 million nucleotide
long DNA molecule for an e. coli. The second term in their equation is
kT ln(1).
The numeral in the parentheses is the total number of sequences which are
capable of forming an e. coli bacteria.(see page 137). Now, in point of
fact, more than one 4 million unit long DNA sequence is capable of forming an
e. coli and this fact has been known nearly as long as DNA has been known. I
don't know how many sequences can form an e.coli, but I would be willing to
bet it is far, far more sequences, than I have fingers and toes. Some strains
of e.coli will kill you if you eat them in an undercooked hamburger. Other
strains live happily in your intestines. I have mentioned this to both
Walter, and Charles. Neither has chosen to respond to it. I would mention
it to Olsen but I don't know him. I fear that Charles is mad at me now
because I can be a pain in the... well you know what.
My biggest complaint against christians in apologetics is that we are not
rigorous enough. We accept what sounds good without really thinking the
issue through enough.
glenn