[adrian_b]

While that is an interesting fact about the evolution of ribosomes, no kind of ribosome could have ever appeared, except after the process of RNA replication was already a perfected process.

Otherwise the first ribosome would have disappeared soon after it was first assembled, without leaving any descendants.

The first ribosome was probably made only of RNA, as there were no other ribosomes to assemble the ribosomal proteins, so it is not surprising that at some point some of the ribosomal RNA segments were replaced by proteins transcripted also from some ribosomal RNA segments, if that happened to improve the ribosome structure.

[jacquesm]

Many statements made with certainty about an era about which we know absolutely nothing for sure.

[adrian_b]

While there are many things that we do not know about that era, there are also many other things about which we are completely sure.

For example we know for sure that all the chemical reactions required to assemble the components of a living being required the same amount of energy then as they require now, so either there was a source of energy large enough to enable them, or they were impossible.

Other things may not be completely certain, but they are overwhelmingly plausible, for example if we know that the transition from a more primitive structure to a more complex structure required 5 improbable mutations, we can be pretty sure that there is no chance that all those changes happened simultaneously, but they must have happened in a certain sequence, one by one.

If moreover, there are some causal links between those events, so that some of them cannot happen unless others already happened, then we may be able to determine which was the sequence of those 5 events, with considerable certainty.

While we are unable yet to estimate confidently which of many possible things really happened in the distant past, we can actually exclude with great certainty many other things, about which we can say for sure that they did not happen, because they contradict fundamental laws, like the conservation of energy.

Among these things that certainly did not happen are some previously popular theories about the origin of life, whose authors did not attempt to analyze them in enough detail to see if they are compatible with the known chemistry and physics, e.g. the ancient theory of the "organic soup" or the more recent theory of the "RNA world".

[kubanczyk]

It's good to make bold statements, because if anything it enables clear and convincing counter-arguments to show up.

[alextheparrot]

Couldn’t one take the view point that the formation of a transient ribosome could have created the conditions to solve replication?

This route would be much more of a dance than what you’ve implied. A transient ribosome makes a protein-based RNA replicase, replicase copies all local the RNAs including the RNA ribosomes. This process would eventually result in a large number of ribosome RNAs and replicase proteins without the need to have a “perfected process” prior to either step.

The whole process would be much messier than what we see today after millions of years of refinement, of course. The stability of an arbitrary RNA polymer is also increased by the presumed lack of RNases as well.

It has been a few years since I took a grad course covering the ribosome, so excuse my lack of currentness if new research has discounted this.