When Did Life Likely Emerge on Earth in an RNA‐First Process?

Benner, Steven A.; Bell, Elizabeth A.; Biondi, Elisa; Brasser, R.; Carell, Thomas; Kim, Hyo‐Joong; Mojzsis, Stephen J.; Omran, Arthur; Pasek, Matthew A.; Trail, Dustin

doi:10.1002/syst.201900035

Cited by 104 publications

(141 citation statements)

References 189 publications

(292 reference statements)

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“…The likely impact history of Earth, however, provides these compounds in a model that is consistent with quantitative analyses of the amount of siderophilic "iron-loving" metals (e.g., Au, Pt, Ir, Os) in the Earth's mantle [56]. After core closure, these siderophiles likely were delivered by one (or a few) relatively large impacting bodies; this small number is suggested by the relative amounts of siderophiles on Earth and the Moon.…”

Section: The Need For Reduced Precursorsmentioning

confidence: 62%

Prebiotic Chemistry that Could Not Not Have Happened

Benner

Kim

Biondi

2019

Life

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We present a direct route by which RNA might have emerged in the Hadean from a fayalite–magnetite mantle, volcanic SO2 gas, and well-accepted processes that must have created substantial amounts of HCHO and catalytic amounts of glycolaldehyde in the Hadean atmosphere. In chemistry that could not not have happened, these would have generated stable bisulfite addition products that must have rained to the surface, where they unavoidably would have slowly released reactive species that generated higher carbohydrates. The formation of higher carbohydrates is self-limited by bisulfite formation, while borate minerals may have controlled aldol reactions that occurred on any semi-arid surface to capture that precipitation. All of these processes have well-studied laboratory correlates. Further, any semi-arid land with phosphate should have had phosphate anhydrides that, with NH3, gave carbohydrate derivatives that directly react with nucleobases to form the canonical nucleosides. These are phosphorylated by magnesium borophosphate minerals (e.g., lüneburgite) and/or trimetaphosphate-borate with Ni2+ catalysis to give nucleoside 5′-diphosphates, which oligomerize to RNA via a variety of mechanisms. The reduced precursors that are required to form the nucleobases came, in this path-hypothesis, from one or more mid-sized (1023–1020 kg) impactors that almost certainly arrived after the Moon-forming event. Their iron metal content almost certainly generated ammonia, nucleobase precursors, and other reduced species in the Hadean atmosphere after it transiently placed the atmosphere out of redox equilibrium with the mantle. In addition to the inevitability of steps in this path-hypothesis on a Hadean Earth if it had semi-arid land, these processes may also have occurred on Mars. Adapted from a lecture by the Corresponding Author at the All-Russia Science Festival at the Lomonosov Moscow State University on 12 October 2019, and is an outcome of a three year project supported by the John Templeton Foundation and the NASA Astrobiology program. Dedicated to David Deamer, on the occasion of his 80th Birthday.

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Section: The Need For Reduced Precursorsmentioning

confidence: 62%

Prebiotic Chemistry that Could Not Not Have Happened

Benner

Kim

Biondi

2019

Life

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“…Despite this, no scenario yet exists that displays all of these phenomena. 64 Our results suggest that alternative ancestral proto-nucleic acid monomers and oligomers, which can be formed and oligomerized under prebiotic conditions, hold the potential to address some of these difficulties. We hope this work will help inspire further exploration of this possibility.…”

Section: Resistance Of Depsipeptide Nucleic Acids To Hydrolysismentioning

confidence: 85%

Depsipeptide nucleic acids: prebiotic formation, oligomerization, and self-assembly of a new candidate proto-nucleic acid

Hud

Fialho

Karunakaran

et al. 2020

Preprint

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The mechanism by which genetic polymers spontaneously formed on the early Earth is currently unknown. The RNA World hypothesis implies that RNA oligomers were produced prebiotically, but the demonstration of this process has proven challenging. Alternatively, RNA may be the product of evolution and some, or all, of its chemical components may have been preceded by functionally analogous moieties that were more readily accessible under plausible early-Earth conditions. We report a new class of nucleic acid analog, depsipeptide nucleic acid, which displays several properties that make it an attractive candidate for the first informational polymer to arise on the Earth. The monomers of depsipeptide nucleic acids can form under plausibly prebiotic conditions. These monomers oligomerize spontaneously when dried from aqueous solutions to form nucleobase-functionalized depsipeptides. Once formed, these depsipeptide nucleic acid oligomers are capable of complementary self-assembly, and are resistant to hydrolysis in the assembled state. These results suggest that the initial formation of primitive, self-assembling, informational polymers may have been relatively facile.

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“…A synthesis of paleontological, phylogenetic and theoretical evidence indicates that the origin of life on Earth required at most O(100) Myr after its formation (Dodd et al 2017;Betts et al 2018;Benner et al 2019). On the other hand, the emergence of complex multicellular life, required a few Gyr, although this delay was partly a consequence of low atmospheric O 2 (Knoll 2015).…”

Section: Prospects For Complex Lifementioning

confidence: 99%

Implications of Abiotic Oxygen Buildup for Earth-like Complex Life

Lingam

2020

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One of the chief paradoxes of molecular oxygen (O 2 ) is that it is an essential requirement for multicellular eukaryotes on Earth while simultaneously posing a threat to their survival via the formation of reactive oxygen species. In this paper, the constraints imposed by O 2 on Earth-like complex life are invoked to explore whether worlds with abiotic O 2 inventories can harbor such organisms. By taking the major O 2 sources and sinks of Earth-like planets into account using a simple model, it is suggested that worlds that receive time-averaged X-ray and extreme ultraviolet fluxes that are 10 times higher than Earth might not be capable of hosting complex lifeforms because the photolysis of molecules such as water may lead to significant O 2 buildup. Methods for testing this hypothesis by searching for anticorrelations between biosignatures and indicators of abiotic O 2 atmospheres are described. In the event, however, that life successfully adapts to high-oxygen environments, these worlds could permit the evolution of large and complex organisms.

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When Did Life Likely Emerge on Earth in an RNA‐First Process?

Cited by 104 publications

References 189 publications

Prebiotic Chemistry that Could Not Not Have Happened

Prebiotic Chemistry that Could Not Not Have Happened

Depsipeptide nucleic acids: prebiotic formation, oligomerization, and self-assembly of a new candidate proto-nucleic acid

Implications of Abiotic Oxygen Buildup for Earth-like Complex Life

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