@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.
