[Winstonm]

http://www.bioedonli...ws.cfm?art=5277

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An elegant experiment has quashed a major objection to the theory that life on Earth originated with molecules of RNA.

"This is extremely strong evidence for the RNA world," says Donna Blackmond, a chemist at Imperial College London

[PassedOut]

Interesting piece. Thanks for the link!

[helene_t]

The RNA theory has been weakened in the later years as the DNA theory got more support, but maybe RNA is back on the stage. As I understand it, mainstream abiogenesis is either RNA or DNA based, and all the other contesters are mavericks. Some of them quite fascinating. I think Richard Dawkins' pet theory involving clay is cute but probably nuts. Just my superficial impression, I don't really claim to understand these issues.

The RNA theory raises the question what kind of environment could preserve RNA structures for long enough for it to evolve, the DNA theory from the problem of whether/how DNA could synthesize proteins. So I suppose the issue is which of the two problems is easier overcome. I suppose this is very interesting for people in biochemistry. Personally I don't have an opinion either way.

But an RNA theory may be unattractive for those charmed by astrobiology, as I suppose we wouldn't find RNA on meteorites. But OK we could go looking for RNA on the moons of Jupiter, for example.

[Winstonm]

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The RNA theory raises the question what kind of environment could preserve RNA structures for long enough for it to evolve, the DNA theory from the problem of whether/how DNA could synthesize proteins

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The problem that DNA has always had and the legitimate difficulty pointed to by creationists is the which came first notion: DNA or proteins, and if I remember correctly this is what Dawkins was trying to overcome with his clay hypothesis.

The RNA theory answers the question of which came first in a unique way - it says neither one. Of course, it is impossible to construct the exact conditions and replicate the birth of life, but the RNA theory does provide a fascinating (and more in line with evolutionary methods) starting point. In RNA theory, both DNA and its enzymatic proteins would have evolved from simpler RNA.

[el mister]

The Clay theory is from a chap called Graham Cairns-Smith, nothing to do with Dawkins. Dawkins did, however, mention it favourably in one of his books, which is perhaps why his name is getting associated with it, such is his influence.

The clay theory (briefly, for anyone interested) is a very thought-provoking and creative idea, but still very speculative. The idea that clays and rocks were important in pre-biotic chemistry is not in question. The inorganic metal ions present have the capacity to catalyse all sorts of simple organic reactions, of the type important in creating the building blocks of life. What Cairns-Smith does is go way beyond this, and posits that inorganic clays actually formed the first genes.

The crystal structure of clays can be thought of as a crude information storage medium, which (may be) capable of propagation and hereditary transfer of information. CS argues that this was the first primitive gene pool - once organic media was established it 'took over' - his book on this subject is actually called Genetic Takeover. This 'takeover' concept seems to be pretty solid, although the specific case of rocks - RNA is open to question. IIRC he speculated that the information content of the crystals would directly influence the structure, and hence information contained, of RNA.

There is no 'DNA' theory of abiogenesis that I'm aware of - RNA has been the main player in pre-biotic chemistry for decades as it is an evolutionary precursor to DNA. The paper referenced in the OP came out last year and is a landmark work, because it provides a very plausible chemical scenario for pre-biotic nucleotide synthesis. Its also very inspirational as a piece of science in general, as it shows what can be achieved if you ask big questions and do not get sidetracked by the trends and modes of the day - something very hard to do in the modern funding environment.

[helene_t]

Thanks for this el mister, sounds like you know more about this issue than I do

[Winstonm]

Yes, thanks for sharing your knowledge, el mister. There is also this from 2009 about self-replicating rna that mutates: http://www.rsc.org/chemistryworld/News/200...ry/09010901.asp

Althought abiogenesis can never be duplicated, it does look like science grows closer and closer to a rational explanation of how it may have occured.

[Winstonm]

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As I understand it, mainstream abiogenesis is either RNA or DNA based,

Helene,

I don't claim to be in your league in scientific knowledge, but from my readings it appears that abiogenesis from a DNA model is pointed to by Creationists as impossible and thus disproving a naturally occuring abiogenesis.

The RNA model attempts to show a precursor to DNA that would support a spontaneous and naturally occuring abiogenesis.