Reality of the Emergence of Life-Like Systems from Simple Prebiotic Polymers on Primitive Earth

A Hypothesis: Life Initiated from Two Genes, as Deduced from the RNA World Hypothesis and the Characteristics of Life-Like Systems

“…However, experimental and empirical evidence has not validated this. On the contrary, RNA molecules possess both informational and biological functions in vivo and presumably also in simulated primitive Earth environments, although prebiotic replication has not yet been elucidated in entirely aqueous solutions [ 12 ], and the RNA world hypothesis is extensively evaluated [ 13 , 14 , 15 , 16 ]. In other words, although DNA and RNA can preserve genotypic and phenotypic functions that are coded with sequences of nucleotide residues, protein-like molecules do not have the capability for storing information in this manner [ 12 ].…”

“…Phylogenetic trees suggest that the last common ancestor of the present organisms (LUCA) could have been hyperthermophilic [ 29 , 30 ]. Since the LUCA is not the origin of all life, the origin of life at low temperatures cannot be ruled out [ 14 , 15 , 31 , 32 , 33 , 34 ]. Organic molecules can maintain biological functions at temperatures over 100 °C, since RNA molecules play biological functions at temperatures over 100 °C in modern hyperthermophiles.…”

“…Organic molecules can maintain biological functions at temperatures over 100 °C, since RNA molecules play biological functions at temperatures over 100 °C in modern hyperthermophiles. However, it is important to consider that the hydrothermal origin-of-life hypothesis [ 32 , 33 , 34 ] would be contradictory to the RNA world hypothesis, when considering whether biomolecules could have accumulated and biomolecules could have expressed biological functions under hydrothermal conditions [ 14 , 15 , 34 , 35 ].…”

“…The shortest half-life of these molecules is on the millisecond scale, even at extreme temperatures around 300 °C. This rate corresponds to the reaction rate of modern enzymes [ 15 , 34 , 49 ]. Our results demonstrated that RNA molecules could have accumulated even under hydrothermal conditions since their accumulation is determined by both the formation and degradation of RNA.…”

“…It is indeed difficult to distinguish the border of the circular network since all organisms and all ecosystems link to each other more or less on the Earth. The biological processes involved in the circular network occur at very high reaction rates, and the reaction rates are adjusted to a narrow range of reaction rates by enzymes in modern metabolic processes [ 15 , 49 , 64 , 65 ]. If one traces back this trend to the origin of life, the elemental reaction processes had very slow rates without enzymes (or ribozymes) and a large range of reaction rates.…”