Paul Nelson: Testing for Common Descent (Signal + Noise?)


(Paul A Nelson) #24

Thanks, y’all. Keep the comments coming, and don’t forget to vote on the pre-Cambrian mammal test.

I’ll do an omnibus reply tonight.

(Paul A Nelson) #25

And this “non-compatible DNA” could not have stemmed from the Last Universal Common Ancestor because…

I’m not being obtuse – I would like you to make the argument against UCD, on the basis of this postulated counterfactual observation, explicit.

(Paul A Nelson) #26

Let’s stipulate that, for any cell on Earth, a ribosome is needed to transfer information from nucleic acid to proteins. That’s not a common ancestry or design claim: it’s just that we don’t know of any other way of building proteins.

What variations in ribosomal structure could not have evolved from the ribosome present in LUCA?


I don’t know about ribosomes, but transfer RNA’s certainly have a lot of room for variation.


The D-loop and T-loop are involved in binding to the enzymes that link the amino acid to the transfer RNA. The anti-codon is not involved in the specific attachment of the amino acid to the acceptor stem, but it is responsible for binding to the complementary bases on the messenger RNA. Therefore, it would be pretty simple to mix and match the loops and anti-codons. For a designer this would be extremely simple.

(Timothy Horton) #31

Sorry but I have no interest in playing your silly rhetorical “gotcha!” games. You asked for potential falsifications of UCD, I gave you three. Suppose you return the favor. Please tell us what observations if made would falsify the Intelligent Design of biological life?

(Neil Rickert) #33

There was a point?

Actually, I think the point of the thread was there in the opening post:

However, @pnelson has failed to tell us why he sees axioms as dangerous.

(Paul A Nelson) #34

I’m focusing on the non-compatible DNA test. But since you can’t, or won’t, explain why this could not have evolved from LUCA, I’ll say that it could have evolved from LUCA.

We simply don’t know the pathway yet.

(Paul A Nelson) #35

Axioms are wonderful in geometry, logic, mathematics.

In a science that’s supposed to be testable against observation? Not so much.

(John Mercer) #41

But why don’t you present some actual observations, instead of what we might expect people to say about them?

It seems to me that you’re far more interested in rhetoric than you are in evidence. Is that correct, or am I misinterpreting something?

(Neil Rickert) #45

In mathematics, axioms are abstract.

In science, what you are describing as axioms are actually laws that connect our linguistic expression to reality. Without such connecting, we would not have an science.

So they are still wonderful. But their role is not the same as the role of axioms in mathematics.

(Arthur Hunt) #49


Why stipulate this? And what does “transfer information from nucleic acid to protein” even mean?

Not true. And also quite beside the point. Unless you are suggesting that the only sort of life that can possibly exist is life as we know it in the here and now. This is some sort of logical transgression, that I am sure some of the better minds here can explain.

I have no idea what this question means.

I will re-state my point - any life that does not have at its core rRNA cannot share an ancestry with, say, E. coli, or rice, or yeast, or humans. Or any of the many, many forms of rRNA-based life that we see on Earth.

For example, Fox’s cells, the ones that grow, divide, metabolize, respond to stimuli, evolve, and otherwise behave as other sorts of living cells - these clearly and plainly do not share a common ancestry with extant life as we know it, or with any extinct species. In fact, as I type these words, it occurs to me that they disprove the proposition that all life forms on Earth share a common ancestry. They just don’t refute the obvious fact that Paul doesn’t like, namely that all rRNA-based life in fact does share a common ancestry.

(Arthur Hunt) #50

Maybe it helps to point out that the animal lineage is such a tiny, almost irrelevant twig on the tree of life that a total revamping of our picture of this twig would have almost zero bearing on the proposition that all life shares a common ancestry.

(Blogging Graduate Student) #51

I suppose it wouldn’t necessarily change how we about non-animal clades, but I think it would influence our thinking on UCD. Being wrong about something as well studied as the fundamental animal phylogeny that has stood for over a century would probably make us seriously reconsider other relationships and seriously think about alternative explanations to UCD.

(John Mercer) #52

I find it interesting that you are being specific about rRNA, while Paul refers to ribosomes and their structure. It’s as if he is avoiding the fact that the Intelligent Designer chose a ribozyme for such an essential function.

(John Mercer) #54

In the 1970s, we had the axiom DNA->RNA->protein->catalysis. (Of course, DNA replicates and should have an arrow looping around to itself, but I don’t know how to do that in text.)

How many Nobel Prizes have been awarded for making observations that have modified that axiom?

(Paul A Nelson) #55

I’m happy to entertain that.

But, if all organisms on Earth share rRNA, and this confirms their common ancestry, you should be able to tell me what variations in rRNA, or in ribosomal structure more generally, cannot occur, given LUCA and the requirements for producing functional proteins.

Otherwise I have no way of testing your claim.

(Blogging Graduate Student) #56

Which modifications do you have in mind?

(Arthur Hunt) #57

I’m still not sure I understand this line of reasoning. However, it is pretty clear that variants in which the RNA-based catalytic core of the ribosome (the peptidyl transferase) has been inactivated cannot survive.

(Note to Paul - I corrected a spell-checker error that will carry through to replies - sorry for not catching it…)

(Paul A Nelson) #58


One can modify or even refute a universally quantified empirical generalization – it isn’t properly an “axiom,” although English allows such usage – such as DNA>RNA>protein>catalysis, in the light of observation. Howard Temin, Thomas Cech, and so forth.

One cannot modify, in the light of observation, Euclid’s postulates. (The parallel postulate turned out to be logically independent of the others; it wasn’t refuted by observation.)

I’m looking for the observations, real or counterfactual, that would allow one to modify or refute the proposition, “All organisms on Earth share a common ancestor: LUCA.”

(Paul A Nelson) #59

Thanks. More on this later this evening.

Swapping Iron For Magnesium in the Ribosome