Emergence of life in an inflationary universe

TL;DR

This paper explores how the vast size of an inflationary universe makes the spontaneous formation of long, self-replicating RNA molecules plausible, providing a potential solution to the origin of life problem.

Contribution

It derives a quantitative relation between RNA length and universe size, showing that large universes can naturally produce life-essential polymers through random processes.

Findings

Long RNA can form in an inflationary universe due to its size.

Minimum RNA length for abiogenesis is around 20 nucleotides.

Formation of longer, self-replicating RNA is statistically feasible in large universes.

Abstract

Abiotic emergence of ordered information stored in the form of RNA is an important unresolved problem concerning the origin of life. A polymer longer than 40--100 nucleotides is necessary to expect a self-replicating activity, but the formation of such a long polymer having a correct nucleotide sequence by random reactions seems statistically unlikely. However, our universe, created by a single inflation event, likely includes more than $10^{100}$ Sun-like stars. If life can emerge at least once in such a large volume, it is not in contradiction with our observations of life on Earth, even if the expected number of abiogenesis events is negligibly small within the observable universe that contains only $10^{22}$ stars. Here, a quantitative relation is derived between the minimum RNA length $l_{\min}$ required to be the first biological polymer, and the universe size necessary to expect the formation of such a long and active RNA by randomly adding monomers. It is then shown that an active RNA can indeed be produced somewhere in an inflationary universe, giving a solution to the abiotic polymerization problem. On the other hand, $l_{\min}$ must be shorter than $\sim$20 nucleotides for the abiogenesis probability close to unity on a terrestrial planet, but a self-replicating activity is not expected for such a short RNA. Therefore, if extraterrestrial organisms of a different origin from those on Earth are discovered in the future, it would imply an unknown mechanism at work to polymerize nucleotides much faster than random statistical processes.