Responding to "LUCA's Paradox[es]" by Finding Truth (@Ahmed_AbdelSattar)

@Ahmed_AbdelSattar recently made a video called “LUCA’s Paradox” where he outlined issues he has with the idea that life evolved from a universal common ancestor. Specifically a common ancestor that was an RNA-based organism.

Now, you might think that, since all organisms (unless you count viruses) have DNA, the common ancestor also had DNA. However, there are some clues that suggests that DNA-based genomes evolved independently Bacteria and Archaea after they diverged from LUCA. For one, some of the proteins involved in DNA-replication are unrelated. This paper discusses this in more detail:

Ahmed also used an image of this paper in his video, but he cited this paper as
“Speculation about LUCA evolving viable RNA error-correction:”
But that is NOT the title of the paper. This isn’t how you properly cite your references @Ahmed_AbdelSattar

Now, moving onto the “paradoxes”. After viewing them, most of them aren’t really paradoxes in the strict (Logically self-contradictory) sense, just questions he think are not answerable, but semantics aside:

#1 How was it possible for RNA-based life to survive and stabilise to become the root of the tree of life, given the obvious instability and vulnerability of RNA and absence of error correction mechanisms?!

Well, firstly, in the paper that you cited as “Speculation about LUCA evolving viable RNA error-correction:” it gives reasons for why LUCA likely did possess error correction mechanisms. Furthermore, this question has largely been answered by Carl Woese of life before the Darwinian Threshold wherein LUCA and pre-LUCA organisms weren’t discrete entities. Strict individuality was not yet established. Instead, they continuously exchanged genetic and other material, such that together they evolved as one unit, which as a whole is more robust against the errors of replication and translation that occurred locally.

#2 How come, if LUCA was an independently living RNA-based life form, the only available RNA-based organisms today, (RNA viruses), cannot lead an independent life, and can only replicate in the context of a host.

Here the previous answer is relevant here. Individuality wasn’t a thing yet during the world before and up to LUCA. So LUCA wasn’t “independent”. When DNA evolved, it was stable enough such that you could construct large genomes that all code for the necessary genes for metabolism, translation, etc (which viruses cannot carry) which are able to sustain individuality in the form of independent cells. Although there are DNA-based organisms that are not entirely independent. Like us heterotrophs who need everything, unable to fix carbon, nitrogen and sulfur, not to mention all the vitamins and essential amino acids that were are not able to synthesize ourselves. We have out-sourced parts of our metabolism.

#3 And if those error correction mechanisms came about by evolution, then how come after billion sof years of evolution, viruses did not acquire these errors correction capabilities that could protect them from attenuation due to excessive mutation.

He actually answered this question himself in his #4 slide (showing the human and chimp diverging from a common ancestor). Asking why viruses haven’t evolved to become independent replicators with error correction, is like asking why chimps haven’t evolved into humans yet? Why should they? Evolution isn’t progressing to some predetermined goal. I have explained this to him in my first commend on this forum on “Human evolution discussion with Ahmed”. This isn’t a paradox.

#5 DNA needs enzymes to be replicated and transcribed, but the enzymes themselves need DNA to be produced!! So, if indeed DNA life emerged from RNA life, which has emerged first and how? The enzymes or the DNA?

Enzymes don’t need the DNA. In this question, RNA life is already a given and if you have the RNA, you can make the proteins using only RNA. Bear in mind, messenger RNA, transfer RNA and ribosomes, etc are all made of RNA. Even the proteins that are part of the ribosomes aren’t vital, the actual working bits of the ribosome that does the catalytic work is RNA based. That’s why this paradox has been long answered by the RNA world proposal (just to be clear, I am not arguing for RNA or genetics first, that’s different. I am more in favor of metabolism first, but that’s a different story).

#6 If we assume that DNA0based life emerged by change through mutation, and in the outset in the absence of error correction mechanisms, then how did it survive until it “evolved” the error correction mechanisms?! Is it possible to evolve correction through the accumulation of mutation errors in the first place?

The answer is pretty much the same as the answer to #1

#7 Likewise, if we stretch our imagination and assume DNA-based life came gradually, and in the absence of error correction it somehow became robust enough to survive long enough until error correction evolved, then where are those clades that are DNA-based living organisms without error correction?!! That is an obvious contradiction with the fact that all DNA-based life (that we know of) has error correction.

We have DNA viruses without the same error correction mechanisms, but if viruses they don’t count and we need cellular life without error correction, then a simple answer that can be give is this:…they are extinct. This is obviously not contradictory.


Hi @Nesslig20 ,
Would you like to have a video discussion about the topic?

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I just want to add here that I think there’s now good evidene that LUCA was distinct from the lineage of so-called “progenotes”(using Carl Woese’s term) from which it evolved, and even if LUCA itself had an RNA-based instead of DNA-based genome, it also had an effectively complete “modern” translation system with all amino acids having assigned codons in tRNA and aaRS enzymes (so nothing prevents it from carrying error correction, RNA/DNA repair and maintenance protein enzymes), and there is good evidence that it was a cellular lifeform.

For example, membrane A- and F-type ATP synthases are pretty much universally distributed in archaea and bacteria, respectively(and so since it has a molecular machines that functions by exploiting membrane potential to do mechanical work, it must have a membrane), and the last universal ancestor is also inferred to carry membrane translocating proteins:

If it has a membrane(we don’t have to know the exact nature of hte sort of lipid that membrane was based on), a translation system, and a genome(whether RNA or DNA), it is a cellular lifeform and by any sensible definition such a cell would constitute an individual.


Not only that. But also because, in part, their high mutation rates are critical for their ability keep up in the evolutionary arms-race with their hosts.


Why not discuss it here? Start a fresh thread and lay out your arguments in detail for the paradoxes of LUCA and maybe one or two people only will respond to them in depth.


Because I have already put the arguments in the video, and I have put my references… maybe if someone, or more than one, is interested to go into a discussion about each point, then it will be a good discussion!

I have nothing against a discussion here too… but seven points in the same time will be difficult :slight_smile:

No, I’d rather have it on a written format. This is a particularly complex subject, and I find it easier to respond when I take the time to think what to write and check sources, etc.


Cool. Thanks for the paper. Certainly keeping that in my personal archive.

On second thought, although my answers would’ve been applicable to the progenotes pre-LUCA, perhaps they don’t apply with regard to LUCA proper, which (given your commentary) likely already passed the Darwinian threshold.

About this:

and so since it has a molecular machines that functions by exploiting membrane potential to do mechanical work, it must have a membrane

I have seen suggestions that before membranes, the “cellular” compartments across which chemical potential (e.g. proton gradients) were present were in the pores of alkaline hydrothermal vents. Although, I would think that the proteins you pointed to, such as the F-type ATP synthases, would require some form of lipid based membranes to operate in.


Based on the interaction you had with Joshua and the little we had here on PS, I would be wary about going into a live debate with you. It would be better if I vetted your claims and any evidence you have for them before engaging you live. That way I get to know any misunderstanding (which you have shown severally) you have, as well valid arguments, and be better prepared to deal with them.

If you want there can be one thread for one point and the mods can arrange the discussion in a way that won’t overwhelm you. Only relevant points will be discussed, with their logic and evidence strictly considered.


Some viruses have evolved error-correction capabilities, e.g. coronaviruses:


Fair enough, say what… throw your best arguments and sources at me, and I will respond in what shot.

The first and most obvious point is that the last universal common ancestor was not the first life. They are two very different things.


Sourced facts that show you to be wrong have already been presented. We are now at the point in the discussion where you either present good counterarguments to these facts, or gracefully admit that you were wrong and take down your video because it is misleading.

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Give the man a chance, what he said is not an issue. It is Arafat today and Eid Adha tomorrow, so I can take a break and he can find his best arguments in 48 hours…
It will be fun.

I already made a response to you. If it is too much, you can read my reply and choose which point you would like to start with. Also, bear in mind that some corrections were made by others in this thread already. Copied below:


Did @Ahmed_AbdelSattar see my reply?
Have you picked a point he wants to start with?

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Hi @Nesslig20
I’m currently on a family engagement, and will be onto our discussion on Wednesday, God willing.
Thank you for your patience.

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Hi @Nesslig20
I am back and will be responding to you later tonight…
Meanwhile, I think that some of the topics you raise will also be addressed in the upcoming session 4 which is about RNA World hypothesis… so, maybe a discussion upfront will be also fun.
Talk to you later tonight.

This is one of the main points. It is not enough to say they evolved… the question is HOW! This is the whole point of the paradoxes. It is interesting you are citing one of my papers (as you have rightfully mentioned), so your comment:

There is actually no problem with the citation, because after a very long discussion in the paper, it turns our it is just speculative. The mechanisms quoted for RNA and Protein quality control are in the DNA-based life context, and is not “error-correction” but rather degradation of the faulty parts… meanwhile, real error correction is just a speculative note.

Now, to the paradoxes:

This matter of LUCA not being a discrete entity is not accepted in the mainstream today, to my understanding… meanwhile, I don’t really see how will it materially change the discussion! I also noticed a comment made later in the thread says the same.

I don’t think that you will disagree that this is conjecture and speculation, and the paper you cite is full of it… even it uses the word in the abstract!

I think you are using the same logic as number 1, so may be you should fix the responses to #1 first.

— I would like to close this first point before we move to the next:
Do you agree that there is no basis to accepting an RNA based autonomous organism can survive on its own.