Minimal Complexity Relegates Life Origin Models To Fanciful Speculation
|November 10, 2009||Posted by Robert Deyes under Intelligent Design|
Review Of The Ninth Chapter Of Signature In The Cell by Stephen Meyer
ISBN: 978-0-06-147278-7; Imprint: Harper One
Former Nature editor Philip Ball once commented that ‘there is no assembly plant so delicate, versatile and adaptive as the cell” (1). Emeritus Professor Theodore Brown chose to wax metaphorical by likening the cell to a fully-fledged factory, with its own complex functional relationships and interactions akin to what we observe in our own manufacturing facilities (2). In recent years the seemingly intractable problem of explaining how the first cell came into existence through chance events, otherwise known as the ‘Chance Hypothesis’, has become more acute than ever as scientists have begun to realize that a minimum suite of functional components must exist for cells to be operational. Stephen Meyer’s summary of the current state of this so-called ‘minimal complexity’ research is profoundly insightful:
“The simplest extant cell, Mycoplasma genitalium – a tiny bacterium that inhabits the urinary tract requires “only” 482 proteins to perform its necessary functions and 562,000 bases of DNA…to assemble those proteins…Based upon minimal-complexity experiments, some scientists speculate (but have not demonstrated) that a simple one-celled organism might have been able to survive with as few as 250-400 genes” (p.201).
For renowned biochemist David Deamer the first cell would at the very least have needed a polymerase enzyme to transcribe from a template such as DNA, a constant source of supplementary materials notably nucleotides, amino acids and ATP and enzymes that faithfully carry out DNA replication during cell division (3). To suppose that even a hypothetical first cell would just come together from a gimish of prebiotic compounds undergoing continuous destructive dilution is to appeal to the miraculous (4). Attempts to reconstruct such a cell start off from a fairly elaborate point of departure in which enzymes and other catalysts are already present and functional (5).
Just how important these functional enzymes are was brought to bear in a study led by University of North Carolina biochemist Richard Wolfenden (6). Wolfenden’s team was able to demonstrate how a reaction with a half life of 2.3 billion years occurred in milliseconds when supplied with the necessary enzymes. Such spectacular differences are not uncommon. As Wolfenden remarked:
“What we’re defining here is what evolution had to overcome…the enzyme is surmounting a tremendous obstacle, a reaction half-life of 2.3 billion years…Without catalysts, there would be no life at all, from microbes to humans. It makes you wonder how natural selection operated in such a way as to produce a protein that got off the ground as a primitive catalyst for such an extraordinarily slow reaction.” (6)
Through a molecular technique known as random mutagenesis, scientists have now quantified the amino acid sequence variability that functional proteins can tolerate. Worthy of note in this field is the work of former Cambridge biochemist Douglas Axe whose data forms a pillar for the case that Meyer presents in his book. Using locally-randomized sequence libraries of a portion of the antibiotic resistance enzyme β-lactamase, Axe calculated that somewhere between 1 in 1050 and 1 in 1077 150 amino acid-long protein folds form configurations with a β-lactamase function (7). Of these one in 1050 to 1 in 1074 form folded structures that might perform any number of alternative functions (7).
Based on the structural requirements of enzyme activity Axe emphatically argued against a global-ascent model of the function landscape in which incremental improvements of an arbitrary starting sequence “lead to a globally optimal final sequence with reasonably high probability” (7). For a protein made from scratch in a prebiotic soup, the odds of finding such globally optimal solutions are infinitesimally small- somewhere between 1 in 10140 and 1 in 10164 for a 150 amino acid long sequence if we factor in the probabilities of forming peptide bonds and of incorporating only left handed amino acids.
In a 1981 legal challenge involving the Arkansas Board Of Education, astronomer Chandra Wickramasinghe appeared for the defense as an expert witness. Taking on the dogmatic neo-Darwinist view on the origins of life, Wickramasinghe unwaveringly proclaimed that the probability of obtaining the information necessary for making the simplest cell by chance was 1 in 1040,000 (8). These estimates not only exceeded by many powers of 10 the total number of atoms available in the universe but also closely matched the minimal complexity predictions discussed above. By pulling together these probabilistic threads of evidence in Signature In The Cell, Meyer has relegated naturalistic life origin models to little more than fanciful speculation. His piece-by-piece dismissal of the chance hypothesis is beautifully executed as is the personal narrative that interconnects the various portions of his scientific story.
Additional Literature Cited
1. Philip Ball (2001) Life’s Lesson In Design, Nature, Vol 409 pp. 413-416
2. Theodore Brown (2003) The Art of the Scientific Metaphor, The Scientist, Volume 17, Issue 21, p. 10
3. David Deamer, Jason Dworkin, Scott Sandford, Max Bernstein, Louis Allamandola (2002) The First Cell Membranes, Astrobiology, Volume 2, pp. 371-381
4. Charles Thaxton, Walter Bradley and Roger Olsen (1984) The Mystery of Life’s Origin: Reassessing Current Theories, Published by Lewis and Stanley, Dallas, Texas, pp.42-68
5.Tamsin Osborne (2008) ‘Artificial Cell’ Can Make Its Own Genes, New Scientist,1 April, 2008, See http://www.newscientist.com/article/dn13568-artificial-cell-can-make-its-own-genes.html
6. Without Enzyme, Biological Reaction Essential To Life Takes 2.3 billion Years: 2008 UNC Study, See http://www.med.unc.edu/www/news/2008-news-archives/november/without-enzyme-biological-reaction-essential-to-life-takes-2-3-billion-years-unc-study/?searchterm=Wolfenden
7. Douglas D. Axe (2004) Estimating the Prevalence of Protein Sequences Adopting Functional Enzyme Folds, Journal Of Molecular Biology, pp. 1295-1315
8. See Chandra Wickramasinghe’s testimony at http://www.panspermia.org/chandra.htm