Methinks it is sort-of like two weasels

[Rumraket (Mikkel R.)]

@lee_merrill

@Rumraket

But that can’t tell you that it didn’t evolve for the same reason that such a calculation can’t tell you that a particular set of cards can’t be drawn.

But I’m saying it’s improbable, not that it cannot happen.

And I’m asking what the significance of that statement is, since it can’t rationally tell us that something didn’t evolve.

@lee_merrill

@Rumraket

From the perspective of your great grandparents 10 generations back your existence would seem miraculously remote too. And yet here you are.

Again you are confusing the probability of an event after the fact, with the probability of an event viewed before the fact.

No, me explaining why it isn’t rational to argue against something having occurred by the statement that X is a priori unlikely, with an analogy to your own existence, is not me confusing anything. The analogy simply makes it more obvious why the reasoning you are employing does not support the conclusion you are seeking.

@lee_merrill

Behe’s edge of evolution is helpful here, if two new protein-protein binding sites are the limit of what evolution can do

But we have no reason to think it is. The diametrically opposite is the case. You have unfortunately been misinformed about biochemistry by reading creationist literature I’m sorry to have to tell you.

In fact protein-protein binding is so ubiquitous that it is practically unavoidable by chance, so much so that we know there is selection operating to suppress and reduce the chance occurrence of protein-protein interactions in the cell.

For a nice overview of this phenomenon I recommend this excellent review article:
https://pubs.acs.org/doi/abs/10.1021/acs.chemrev.8b00753

Should one of these protein-protein binding sites however be beneficial, simple and realistic modeling work shows it is easy to select for it instead. It is known that a considerable fraction of proteins are something like one mutation away from forming binding spots on their surface that would make them able to form large fibrils and structures. I have a thread about a year ago where I reference a few papers that detail these phenomena:

An interesting couple of articles on evolution of protein complexes and multimers

I came across this interesting article(pdf here) on how proteins have an easy time forming large multi-protein complexes, so much so that there’s often purifying selection against this tendency: Abstract The self-association of proteins into symmetric complexes is ubiquitous in all kingdoms of life. Symmetric complexes possess unique geometric and functional properties, but their internal symmetry can pose a risk. In sickle-cell disease, the symmetry of haemoglobin exacerbates the effect of a mutation, triggering assembly into harmful fibrils. Here we examine the universality of this mechanism and its relation to protein structure geometry. We introduced point mutations solely designed to increase surface hydrophobicity among 12 distinct symmetric complexes from Escherichia coli. Notably, all responded by forming supramolecular assemblies in vitro, as well as in vivo upon heterologous expression in Saccharomyces cerevisiae. Remarkably, in four cases, micrometre-long fibrils formed…

@lee_merrill

Now if there are selectable stopping-points along the way, we should see flagella being formed today–but we don’t.

How do you know we don’t? What assay did you run, how long did you observe and where? How do you know that some prokaryote out there with some membrane-embedded structure isn’t on it’s way to evolving a flagellum-like structure?