Wednesday, January 23, 2008

Leslie Orgel - Still Speaking Wisely and Openly Even After Death

OK - my mind has been blown. Leslie Orgel, who just passed away recently, has a new Essay in PLoS Biology called "The Implausibility of Metabolic Cycles on the Prebiotic Earth." Anyone interested in the origin of life should check this out.

He had me at the beginning ... and as usual has very clear discussions of the steps needed for life to have originated:
If complex cycles analogous to metabolic cycles could have operated on the primitive Earth, before the appearance of enzymes or other informational polymers, many of the obstacles to the construction of a plausible scenario for the origin of life would disappear. If, for example, a complex system of nonenzymatic cycles could have made nucleotides available for RNA synthesis, many of the problems of prebiotic chemistry would become irrelevant. Perhaps a simpler polymer preceded RNA as the genetic material—for example, a polymer based on a glycerol-phosphate backbone [5] or a phosphoglyceric acid backbone. Could a nonenzymatic “metabolic cycle” have made such compounds available in sufficient purity to facilitate the appearance of a replicating informational polymer?
The paper then discusses details of various metabolic cycles and why the current evidence is not completely convincing in terms of the exact path that was taken in the origin of life. Note to ID supporters - this does not friggin' mean that he is saying life could not have originated from non living systems. He is simply pointing out that our understanding of it is incomplete. As, by the way, is our understanding of how blood works. But that does not stop us from thinking that blood does in fact, well, work.

Anyway, once you get over the fact that some ID supporters will misuse his work, the end is a great call for what needs to be done:

The prebiotic syntheses that have been investigated experimentally almost always lead to the formation of complex mixtures. Proposed polymer replication schemes are unlikely to succeed except with reasonably pure input monomers. No solution of the origin-of-life problem will be possible until the gap between the two kinds of chemistry is closed. Simplification of product mixtures through the self-organization of organic reaction sequences, whether cyclic or not, would help enormously, as would the discovery of very simple replicating polymers. However, solutions offered by supporters of geneticist or metabolist scenarios that are dependent on “if pigs could fly” hypothetical chemistry are unlikely to help

Yes, that is right, he got "if pigs could fly" into a paper. He was a great scientist. And it is nice for me to see one more paper of his. And this one, unlike pigs, can fly forever, because it is truly OA.

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