THE 'FATAL FLAWS' WITH RICHARD CARRIER'S RNA NUCLEOTIDES STUDIES

    

The "Fatal Flaws" with Richard Carrier's 

RNA Nucleotides Studies

(See, "Q's Response to Richard Carrier: About the Debate," for context)

(See also, "Q's Open Challenge to Richard Carrier")

Richard Carrier’s claim:  

"Totani conservatively estimated on existing evidence that we can expect there to have been formed in the early history of the Earth at least 10^25 nucleotides in the requisite environs (which we know, on a basis of evidence, can happen: Biscans 2018; Cafferty et al. 2016...)"

Q's Verdict:

These studies do not support Richard's claim, but instead only evidence that Richard does not carefully read (or selectively reads) his own sources.

Biscans (2018):

Source citation: Biscans, A. (2018). Exploring the emergence of RNA nucleosides and nucleotides on the early Earth. Life, 8(4), 57. 

Summary: This article summarizes the progress made on nucleotide prebiotic synthesis, as well as the problems that still remain to be solved. As such, it supports what I've said (and what everyone else except Richard seems to realize, too) that the origin of life remains an unsolved problem that is assumed to be true, but yet to be empirically demonstrated. Contra Richard, this article does not demonstrate that the formation of "nucleotides in the requisite environs...we know on the basis of evidence, can happen," but is instead evidence that Richard does not carefully read his own sources, or selectively picks and chooses what suits him, while ignoring the rest; like the following quotes, for example (emphasis added):

“Even if some progress has been made to understand the ribose formation under prebiotic conditions, each suggested route presents obstacles, limiting ribose yield and purity necessary to form nucleotides. A selective pathway has yet to be elucidated.”

“The synthesis of nucleosides from sugars and nucleobases in prebiotic conditions is one of the major difficulties encountered, when attempting to resolve the early formation of nucleosides. The reaction between the ribose and nucleobase is thermodynamically unfavorable, leading to poor yields and little selectivity. Only a few examples showing successful synthesis have been reported in the literature…Even though important efforts are made to determine the possible prebiotic conditions for the nucleoside formation from sugars and nucleobases, this strategy leads to significant problems and an alternative approach has been suggested to form nucleosides.”

 

“Possible routes for purine formation still have to be investigated. However, preliminary studies provide potential leads…While promising, these proposed synthetic pathways demand further investigation.”

“Despite great efforts and impressive advancements in the study of nucleoside and nucleotide abiogenesis, further investigation is necessary to explain the gaps in our understanding of the origin of RNA….Assuming that RNA must be 5′-3′-linked, regioselectivity issues have to be overcome…Furthermore, for its genetic role to be realized, RNA must be able to evolve and replicate. Unfortunately, the chemical processes that sustain RNA oligomerization and replication remain unclear.”

"Other than RNA, cells require various chemical subsystems, including peptides for functional support and lipids for compartmentalization. The assumption that one subsystem came first and then generated the others is debated. Consequently, a search for a chemistry that can concurrently deliver nucleotides, peptides, and lipids or for chemistries that can be compatible with each other within the same geochemical environment could provide the most compelling explanation for the origins of life."

Cafferty et al. (2016):

Source citation: Cafferty et al. (2016). Spontaneous formation and base pairing of plausible prebiotic nucleotides in water. Nature communications, 7(1), 1-8.

Summary: This study has nothing to do with RNA nucleotides, but concerns the speculative role in the origin of life of non-covalently bonded, non-linear sequenced (i.e., non-informational) non-canonical nucleotides. The study does, however, note numerous difficulties with RNA nucleotide prebiotic synthesis; which is again evidence that Richard does not carefully read his own sources, or selectively picks and chooses what suits him.

The study Richard cites does not even have anything to do with RNA nucleotides. It’s about non-canonical nucleotides. The investigators created disk-shaped hexad heterocyclic compounds consisting of non-canonical nucleotides stacked on top of each other via noncovalent hydrogen-bonding between the non-canonical nucleotides. There was no true informational-type linear sequencing like we see in covalently-bonded RNA nucleotides. And far from “empirically establishing” claims, the investigators acknowledge the possible relevance of all this for the origin of life is speculative:

 

“[I]t is tempting to speculate that these heterocycles could represent ancestral nucleotides of the contemporary genetic polymers. In particular, the ability for C-BMP and MMP to form noncovalent supramolecular assemblies could have facilitated the prebiotic localization, organization and subsequent linking of these (or similar) nucleotides into covalent polymers that were then capable of storing and transferring information.”

 

But this is all just speculation, as the investigators note, and the “could have facilitated…subsequent linking…into covalent polymers” are just words with no empirical demonstration of how these noncovalent supramolecular assemblies could facilitate such “subsequent [covalent] linking. As I’ve said, the origin of life field is highly speculative.

Figure 4f  Cafferty et al. (2016).

The study does, however, note numerous difficulties involved in RNA nucleotide prebiotic synthesis:

 

“The RNA World hypothesis presupposes that abiotic reactions originally produced nucleotides, the monomers of RNA and universal constituents of metabolism. However, compatible prebiotic reactions for the synthesis of complementary (that is, base pairing) nucleotides and mechanisms for their mutual selection within a complex chemical environment have not been reported.” (emphasis added)

 

“Nevertheless, despite decades of effort, the chemical origin of nucleosides and nucleotides (that is, nucleobases glycosylated with ribose and phosphorylated ribose) remains an unsolved problem” (emphasis added)

“The persistent challenge of finding a simple, robust and plausible prebiotic route to the canonical nucleosides—juxtaposed with the exquisite functionality of RNA—have caused many researches to consider RNA a product of chemical and/or biological evolution.”