The RNA world

The "RNA world" hypothesis suggests that the roles of proteins and enzymes were once played by curled-up RNA strands.

This hypothesis has a great deal of experimental support. In particular there are still RNA enzymes (Ribozymes) in use in modern organisms. Indeed the functional part of the ribosome, (which translates RNA into proteins), is basically a ribozyme.

It doesn't take much imagination to guess that there might once have been more of these things.

However, the "RNA world" is not itself hypothesis a about the actual origin of life - since RNA is not remotely plausible in the role of the first genetic material.

Unfortuately there is a lot of garbage about the RNA world in circulation on the internet, that is liable to confuse and mislead people.

For example:

RNA world hypothesis, for example, suggests that short RNA molecules could have spontaneously formed that would then catalyze their own continuing replication.

- http://en.wikipedia.org/wiki/Origin_of_life

The RNA World hypothesis holds that in the primordial soup (more likely the primordial sandwich), there were RNA and DNA base pairs floating around. Since it is of lower energy for base pairs to form a chain, this would happen with some regularity. However, these chains are not of much lower energy than free base pairs, so the chains would also break apart with some regularity. However, some sequences of base pairs have catalytic properties - catalytic properties which lowers the energy of that same chain being created. As more and more of these RNA chains are created, they catalyze the formation of yet more. This causes chains to form faster than they break down, creating a positive feedback loop.

These chains are proposed to be the first, primitive forms of life.[]''

- http://en.wikipedia.org/wiki/RNA_world_hypothesis

There is a lot of material out there along similar lines.

Nonsense like this makes the RNA world hypothesis appear ridiculous. The problems in the proposed scenario are stupendous. For one thing, nucleotide isomeric impurity blocks replication of RNA. For another, there is no plausible way that primed nucleotides could be supplied.

AFAIK, nobody seriously interested in the origin of life believes this silly hypothesis.

Perhaps proponents of the RNA world should take more care to emphasise that the notion that the RNA world was primitive is not biologically plausible - rather than associating themselves with the idea.

The RNA world was obviously constructed by more primitive agents - (of which there are no shortage of candidates) - rather than forming out of nothing.

The RNA world itself is a fine hypothesis. However, I wish that people would stop muddling it together with a lot of garbage about the RNA world being first.

References

1. The origin of life - a review of facts and speculations
   
2. Prebiotic synthesis of nucleotides
   
3. Constructing an RNA world
   
4. RNA-catalysed nucleotide synthesis
   
5. Synthesis of RNA oligomers on heterogeneous templates
   
6. Surprising fidelity of template-directed chemical ligation of oligonucleotides
   
7. Prebiotic ribose synthesis: a critical analysis
   
8. The improbability of prebiotic nucleic acid synthesis
   
9. The prebiotic role of adenine: a critical analysis
   
10. Prebiotic cytosine synthesis: a critical analysis and implications for the origin of life