Well this seems extremely specious. To presume the entire history of life must remain in existence on a heavily life-colonized world is bizarre reasoning. Any "simple self-replicator" would have long since been exterminated by it's more sophisticated next generation species, not to mention the multiple ages of radically different environmental pressures (i.e. the oxygen apocalypse) in the Earth's history.
You're essentially arguing that the absence today of simple replicating amino-acid organisms somehow implies that they must spontaneously form far far more complex systems to do so: yet the evidence says otherwise - we know for a fact and can observe the existence of purely RNA-based enzymatic systems (https://en.wikipedia.org/wiki/RNA_world) which are curiously involved in things like protein synthesis in our cells today.
You are now committing the other Origin of Life non sequitur that annoys the hell out of me: confusing the statement "the evidence does not require one to believe X" with the statement "the evidence requires on to believe not-X".
I'm not arguing that life must be rare. I'm not arguing that the smallest Darwinian replicator must have billions of atoms. I'm arguing against the PRESUMPTION that there must be a small replicator, and the inference (from that presumption) that life must be common. There is no evidence for such a small replicator (the RNA world work does not provide it). And understand that even if the smallest replicator were much smaller than this billions-of-atoms thing, it could still present a super-astronomical complexity gap.
The evidence for small replicators is that we now have large replicators. Whatever the absolute probabilities are, the relative probability of spontaneous emergence of small replicators is much, much larger than large replicators. Therefore, large replicators most likely evolved from small replicators.
Put another way: the most likely ancestor of all replicators was probably close to the smallest molecule that works.
Ah, this is the inference "we are here, therefore life must be common".
This is bogus, because it ignores Observer Selection. We are not at a randomly chosen planet in the universe (or in a larger multiverse), we are at a planet where there exists observers who could observe life exists. The more uncommon observers are, the more biased our position would be.
Ask yourself: if OoL were exponentially unlikely, requiring super-astronomical numbers of tries to get it to occur, far beyond the number of stars (or even atoms) in our visible universe, what exactly would we see that's different from what we do see? If there is no such thing, how could current evidence rule out that possibility?
I will totally agree that the mechanism by which life arose should be among the easiest routes to life. But this doesn't mean that process was likely in any absolute sense, just that it was among the least unlikely.
I'm not claiming life must be common. The strong anthropic theory explains why we can be having this conversation despite the probability of life emerging being arbitrarily low, so there's no reason to assume the probability of life must be high.
But no matter what that probability is, when there are 2 alternative pathways for a step, we should assume the more likely one. I merely claim that
inorganics -> small replicators -> large replicators
With people as insistently contrarian as you seem to be, I really wonder what alternatives, of how life came about, you are proposing?
Is it really just pure agnostic nihilism along the lines of "We know nothing!"? Or do you know of more reasonable alternative explanations, not investigated in experiments like this?
You're essentially arguing that the absence today of simple replicating amino-acid organisms somehow implies that they must spontaneously form far far more complex systems to do so: yet the evidence says otherwise - we know for a fact and can observe the existence of purely RNA-based enzymatic systems (https://en.wikipedia.org/wiki/RNA_world) which are curiously involved in things like protein synthesis in our cells today.