
The sugar ribose is more quickly phosphorylated compared to other sugars with the same chemical formula but a different shape. This selective phosphorylation could explain how ribose became the sugar molecule in RNA.
Credit: Scripps Research
One fallacy with which anyone who has tried to engage a creationist in debate will soon become familiar is the false dichotomy. This is where a creationist attempts to make a "god of the gaps" argument appear logical by presenting it as a binary choice between something so simplistic or absurd that no serious scientist would argue for it—and "God did it!" In doing so, they ignore the actual scientific explanations and exclude all other plausible natural mechanisms.
A classic example of this is the argument that abiogenesis—often deliberately misrepresented as the spontaneous assembly of a complex, living cell from inorganic materials—is far too improbable to have occurred by chance alone, and therefore must have required a supernatural intelligence. In their minds, the very existence of complex life is "proof" of their particular deity.
This line of reasoning overlooks the crucial role played by natural processes, such as chemistry and physics, and what amounts to an evolutionary process at the molecular level. In such a process, chemical pathways that are more efficient at producing copies of themselves are naturally favoured, leading over time to increased refinement and complexity. For instance, why was the five-carbon sugar ribose selected as the backbone sugar in RNA?
This is the question that two researchers at the Scripps Research Institute have tackled. They demonstrated that ribose is far more efficiently phosphorylated than its alternatives, forming the chemical basis of nucleotides—the building blocks of RNA (and later DNA). This efficiency gave ribose a natural advantage, allowing it to "win" the competition against other sugars.
Their findings show that the emergence of ribose was not the result of random chance, but the predictable outcome of the underlying chemistry and physics. The study has been published in the international edition of the journal of the German Chemical Society, Angewandte Chemie.
The work is also summarised in accessible terms in a Scripps Research press release.