RNA World is the theory that the earliest life forms used RNA to perform functions now carried out by DNA because RNA was more likely to somehow fall into place. From Jordana Cepelewicz at Quanta:
… Perhaps most importantly, an RNA-only world could not explain the emergence of the genetic code, which nearly all living organisms today use to translate genetic information into proteins. The code takes each of the 64 possible three-nucleotide RNA sequences and maps them to one of the 20 amino acids used to build proteins. Finding a set of rules robust enough to do that would take far too long with RNA alone, said Peter Wills, Carter’s co-author at the University of Auckland in New Zealand — if the RNA world could even reach that point, which he deemed highly unlikely. In Wills’ view, RNA might have been able to catalyze its own formation, making it “chemically reflexive,” but it lacked what he called “computational reflexivity.”
“A system that uses information the way organisms use genetic information — to synthesize their own components — must contain reflexive information,” Wills said. He defined reflexive information as information that, “when decoded by the system, makes the components that perform exactly that particular decoding.” The RNA of the RNA world hypothesis, he added, is just chemistry because it has no means of controlling its chemistry. “The RNA world doesn’t tell you anything about genetics,” he said.
Nature had to find a different route, a better shortcut to the genetic code. Carter and Wills think they’ve uncovered that shortcut. It depends on a tight feedback loop — one that would not have developed from RNA alone but instead from a peptide-RNA complex. … More.
Rob Sheldon, our physics color commentator and author of Genesis: The Long Ascent, comments,
Isn’t it amazing how many evolution “solutions” illuminate a problem that was never mentioned previously? The article dishes on RNA-world only because the authors have another “ribosome-world” theory that solves the problem of functional information.
You also notice how these “worlds” are getting ever more complicated? The “first thing” that existed is now billions of times more complicated than coacervates. At what point is it simpler to believe that working cells just “appeared” out of nothing? I mean if you’re going to invoke a miracle, you might as well make sure it is big enough to not need any supporting characters.
Not to worry. This bus makes regular stops at RNA World.
See also: Welcome to “RNA world,” the five-star hotel of origin-of-life theories (Now check out.)