Migrations

Back in March, on my original blog, I mentioned the Creationist arguments on abiogenesis, and perhaps it’s time to revisit just how bad a claim that is, since it’s been brought up again in the Evolution and Design comments section.


The discussion began about the math behind Dembski’s Specification “theory,” which of course relies on ignorance. The more we know about a process, the less Dembski’s estimates of specified complexity have any relevance.

And as such, Salvador and David have retreated to the origin of life, as a specified process – which is of course the motherload of yet-unexplained occurences in the history of life. David says:

Even an extremely optimistic estimate of 50% probability per gene family suggests probabilities less than 1/2^1000, which I think is a tad bit beyond Dembski’s Universal Probability Bound of 10^120!

Good luck in trying to showing abiogenesis to a minimum self reproducing cell within the UPB – AFTER which you get a chance to invoke the wonderous powers of natural selection.

In other words, he’s arguing that it’s improbable that abiogenesis, as understood by Creationists (left side of the image above) could have occurred. And he’d be absolutely correct. What he hasn’t done is refute the power of acid-base and organic chemistries to generated replicating polymers for natural selection to act upon.

But it sounded impressive the way he put it, chock-full of incredulity, didn’t it?

For completeness though, let’s repost the rest of my original piece:

Members of Cornell’s IDEA club on their recently-started blog, The Design Paradigm, are this time pointing to a recent PNAS article on the “Essential genes of a minimal bacterium.” The obvious implication is that, if the simplest known bacterium requires well over 200 genes to survive in modern laboratory conditions, with ample nutrients, etc., it’s inconceivable that it could have evolved from nothingness (a.k.a. that abiogenesis could have occurred without a Creator)?

This isn’t a recent argument, and has been addressed before, as laid out on this Talk Origins article:

Another claim often heard is that there is a “life sequence” of 400 proteins, and that the amino acid sequences of these proteins cannot be changed, for organisms to be alive.

This, however, is nonsense. The 400 protein claim seems to come from the protein coding genome of Mycobacterium genetalium, which has the smallest genome currently known of any modern organism [20]. However, inspection of the genome suggests that this could be reduced further to a minimal gene set of 256 proteins [20]. Note again that this is a modern organism. The first protobiont/progenote would have been smaller still [4], and preceded by even simpler chemical systems [3, 10, 11, 15].

As to the claim that the sequences of proteins cannot be changed, again this is nonsense. There are in most proteins regions where almost any amino acid can be substituted, and other regions where conservative substitutions (where charged amino acids can be swapped with other charged amino acids, neutral for other neutral amino acids and hydrophobic amino acids for other hydrophobic amino acids) can be made. Some functionally equivalent molecules can have between 30 – 50% of their amino acids different. In fact it is possible to substitute structurally non-identical bacterial proteins for yeast proteins, and worm proteins for human proteins, and the organisms live quite happily.

The “life sequence” is a myth.

The rest of the article debunks many of the surrounding claims concerning abiogenesis and the minimal gene set.

References:

• [3] Otsuka J and Nozawa Y. Self-reproducing system can behave as Maxwell’s demon: theoretical illustration under prebiotic conditions. J Theor Biol, 194, 205-221, 1998
• [4] Woese C, The universal ancestor. Proc Natl Acad Sci USA, 95: 6854-6859.
• [5] Varetto L, Studying artificial life with a molecular automaton. J Theor Biol, 193: 257-85, 1998
• [10] Lee DH, Severin K, and Ghadri MR. Autocatalytic networks: the transition from molecular self-replication to molecular ecosystems. Curr Opinion Chem Biol, 1, 491-496, 1997
• [11] Di Giulio M, On the RNA world: evidence in favor of an early ribonucleopeptide world. J Mol Evol, 45: 571-8, 1997
• [12] Ekland EH, and Bartel DP, RNA-catalysed RNA polymerization using nucleoside triphosphates. Nature, 383: 192, 1996
• [15] Lazcano A, and Miller SL, The origin and early evolution of life: prebiotic chemistry, the pre- RNA world, and time. Cell, 85: 793-8, 1996
• [17] Lee DH, Granja JR, Martinez JA, Severin K, and Ghadri MR, A self-replicating peptide. Nature, 382: 525-8, 1996
• [20] Mushegian AR and Koonin, EV, A minimal gene set for cellular life derived by comparison of complete bacterial genomes. Proc. Natl. Acad. Sci. USA, 93: 10268-10273.
• [22] Breaker RR, and Joyce GF, Emergence of a replicating species from an in vitro RNA evolution reaction. Proc Natl Acad Sci U S A, 91: 6093-7, 1994
• [28] Eigen M, and Schuster P, The hypercycle. A principle of natural self-organization. Springer-Verlag, isbn 3-540-09293, 1979