First of all, I should point out that we agreed on the main point of Glenn's
post--the statement that creationists often ignore the fact that more than
one sequence can perform a function and that they often pick the most
complex example for their probability calculations. Unfortunately even many
good critiques, including the Thaxton, Bradley and Olsen references I gave,
often fall into one or both of these pitfalls. My criticisms were directed
at how Glenn was calculating his probabilities in his example to easily
arrive at functional proteins. I pointed out that he: (1) neglected to
include the generation of amino acids from their components; (2) ignored the
problems of enantiomers (optical isomers); (3) picked a sequence too short
to be functional (8 amino acids) for his probability discussions; and (4)
would face problems showing that the conditions favorable to the formation
of proteins actually existed on the early earth and, that if they did occur,
they were an extremely improbable occurance.
On points (1) and (2), Glenn freely admitted the deficiencies of his
probability example and agreed that these two considerations (which lowers
the probability) must be included. He however, maintained that if protein
selection occurred on a worldwide scale over a lengthy period of time that
even highly improbable proteins would emerge. I agree, but that brings us
to point (4) and the choice of favorable initial conditions necessary for
the probability argument to get off the ground. It turns out that the
evidence for these conditions existing on the early earth is very weak and
there is considerable evidence to suggest that conditions were unfavorable
to protien (or RNA, DNA, etc.) development. Glenn's post shows that he is
aware of these difficulties and is willing to agree that there are many
considerations outside the probability issue that are difficult for
abiogenesis. Since this is another whole topic from the original post, I am
not going to pusue it any further (the discussion could go on for weeks)..
The remaining point at which I still disagree with Glenn is the shortest
functional protein sequence. I was very impressed when Glenn actually
provided two examples of 8 amino acid functional proteins. I goofed a
little on this one because it's been so long since I've thought about
biology that I forgot about peptide signal molecules. But I still think
Glenn is missing a very important point. Here are his examples:
GM>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.
Notice that Glenn's two examples have functionality only in the context of a
complex biological organism. The other components in the organism provide
the binding site and all the machinery for carrying out chemical or
metabolic changes in the system and the 8 amino acid molecule is merely
acting as a trigger. You don't have other functional components to do the
heavy lifting in a prebiotic soup. Stick those 8 amino acid fragments into
a prebiotic evolutionary world and their functionality is practically zilch.
To give an analogy, the key in my pocket has the functional ability to
activate my car, but the key alone is a pretty useless means of
transportation. :-) My chemist's gut instinct is still telling me that if
you want a protein that exhibits a useful functionality in a prebiotic
world, you need a lot more than 8 amino acids. My guess is somewhere in the
50-100 amino acid range. Glenn may be right, but he's got to provide a
better example to convince this doubting Thomas.
And finally, I would like to thank Glenn for bringing to my attention new
discoveries (and giving references!) that I knew very little about: the
Murchison meteorite, the findings of directed evolutionary research, etc.
__________________________________________________________
"Looking back, there's a thread of love and grace
Connecting each line and space I've known" -David Meece
==========================================================
Eddie Gene Olmstead, Jr. Chemistry Department
Asst. Professor of Chemistry Gordon College
Email: olmstead@gordonc.edu 255 Grapevine Road
Phone: (508) 927-2300 Ext. 4393 Wenham, MA 01984