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Abiogenesis

Abiogenesis is the natural chemical process by which life arises from non-living matter, transitioning from simple inorganic and organic compounds to self-replicating, metabolizing systems capable of Darwinian evolution.^[1] This process is thought to have occurred on Earth between approximately 4.3 and 3.7 billion years ago, soon after the planet's formation around 4.5 billion years ago, when conditions such as liquid water, energy sources, and essential elements became available; recent studies suggest possible evidence of life as early as 4.1–4.2 billion years ago based on carbon isotopes and microfossils.^[2]^[3]^[4] The concept of abiogenesis contrasts with earlier notions of spontaneous generation, which posited that complex life forms could arise abruptly from non-living materials under everyday conditions; modern science rejects this in favor of gradual, chemistry-driven emergence under primordial Earth environments.^[1] Key evidence includes the oldest undisputed fossils, such as microbial mats dated to 3.7 billion years ago in Greenland, and potential earlier traces like carbon isotopes in 4.1 billion-year-old zircons, indicating that life had already established itself by the late Hadean or early Archean eon.^[2]^[4] Despite the lack of direct fossil or geological records from the exact transition, abiogenesis is supported by laboratory simulations demonstrating the formation of life's building blocks from abiotic precursors. Pioneering experiments, such as the 1952 Miller-Urey experiment, simulated early Earth's atmosphere with gases like methane, ammonia, hydrogen, and water vapor, using electrical discharges to produce amino acids and other organic molecules, providing empirical support for the synthesis of biomolecules under prebiotic conditions.^[5] Leading hypotheses include the Oparin-Haldane primordial soup model, which proposes that organic compounds accumulated in ancient oceans and were energized by ultraviolet light or lightning to form polymers; the RNA world hypothesis, positing self-replicating RNA molecules as the first genetic systems; and metabolism-first scenarios, where autocatalytic chemical networks near hydrothermal vents preceded genetic material.^[1] These theories converge on the idea of dynamic kinetic stability, where replicating systems evolve toward greater complexity through physicochemical principles, bridging abiogenesis with biological evolution.^[1] Ongoing research explores additional venues, such as deep-sea vents or extraterrestrial delivery of organics via meteorites, and emphasizes the role of minerals in catalyzing reactions; while the precise pathway remains unresolved, abiogenesis underscores the continuity between chemistry and biology as a fundamental aspect of life's universality.^[2]

Introduction

Definition and Scope

Abiogenesis refers to the natural process by which life emerges from non-living matter, particularly through the chemical origins of the simplest living systems from inorganic compounds or basic organic precursors on Earth.^[1] This process is estimated to have occurred between approximately 4.3 and 3.7 billion years ago, shortly after the planet's formation around 4.5 billion years ago and the availability of liquid water and suitable chemical environments.^[6] The term encompasses the transition from abiotic geochemistry— involving mineral interactions and atmospheric chemistry—to biochemistry, where complex organic molecules capable of metabolism and replication begin to form.^[7] The scope of abiogenesis research focuses on the stages of chemical evolution that bridge prebiotic molecules, such as amino acids and nucleotides, to self-replicating systems like protocells or RNA-based entities, without invoking life-from-life (biogenesis).^[1] It is inherently Earth-centric, drawing from geological and atmospheric evidence of the Hadean and Archean eons, yet its principles are universally applicable, informing astrobiology's quest to understand life's potential emergence on other worlds.^[7] Key to this field is the development of testable, naturalistic hypotheses grounded in empirical experimentation and observation, distinguishing it from non-scientific explanations such as creationism or intelligent design.^[2] Early experiments, like the 1953 Miller-Urey simulation of a reducing atmosphere producing amino acids from simple gases, have provided foundational evidence for the plausibility of prebiotic synthesis under primordial conditions.^[5]

Historical Overview

The concept of abiogenesis, or the origin of life from non-living matter, traces its roots to ancient philosophical speculations, particularly the theory of spontaneous generation proposed by Aristotle in the 4th century BCE. Aristotle posited that certain forms of life, such as insects and small animals, could arise directly from decaying organic matter or environmental elements like mud and water, without the need for pre-existing parents, viewing this as a natural process driven by the inherent potential of matter. This idea dominated biological thought for over two millennia, influencing scholars from antiquity through the Middle Ages and into the early modern period.^[8] In the 19th century, advancements in microscopy and experimentation challenged spontaneous generation, marking a pivotal shift from vitalistic views—which attributed life to an immaterial "vital force"—to a more materialistic understanding of biological processes. Louis Pasteur's landmark experiments in the 1860s, particularly his 1861 memoir demonstrating that microbial growth in sterilized broth required airborne contaminants, conclusively disproved spontaneous generation for microorganisms under observable conditions, redirecting scientific inquiry toward the possibility of life's emergence in a primordial Earth environment.^[9] This intellectual transition undermined vitalism, promoting the idea that life could arise through purely physical and chemical mechanisms, as evidenced by the growing acceptance of mechanistic biology in the late 19th and early 20th centuries.^[10] The modern theoretical foundation for abiogenesis was laid in the 1920s with the independent proposals of Alexander I. Oparin and J.B.S. Haldane, who envisioned chemical evolution in Earth's early reducing atmosphere leading to the formation of complex organic structures like coacervates—droplet-like aggregates of macromolecules that could exhibit primitive metabolic and replicative properties. Oparin outlined this in his 1924 pamphlet Proiskhozhdenie zhizni, arguing for a gradual progression from inorganic compounds to self-sustaining biochemical systems.^[11] Haldane expanded on similar ideas in his 1929 essay "The Origin of Life," suggesting that ultraviolet radiation and electrical discharges could synthesize organic molecules in a "primordial soup," setting the stage for life's emergence.^[12] These hypotheses marked the transition from speculative philosophy to a testable scientific framework, paving the way for experimental investigations in the mid-20th century.^[11]

Early Conceptual Frameworks

Spontaneous Generation

Spontaneous generation refers to the historical hypothesis that living organisms could arise directly from non-living matter under ordinary environmental conditions, a concept rooted in observations of apparent life emerging from decaying substances.^[13] This theory posited that complex life forms, such as insects or microbes, developed spontaneously from organic decay products like rotting meat or nutrient-rich broths.^[14] A classic example involved the belief that maggots formed directly from decomposing flesh without parental involvement.^[15] The first major experimental challenge to spontaneous generation came in 1668 from Italian physician Francesco Redi, who tested the idea using meat in jars.^[15] Redi placed pieces of meat in open jars, where maggots appeared due to fly eggs, and in covered jars (using gauze or fine mesh), where no maggots developed despite decay odors permeating the air.^[14] His controlled setup demonstrated that maggots arose from fly eggs, not the meat itself, though Redi allowed for possible spontaneous origins of parasites.^[16] In 1745, English clergyman and naturalist John Needham conducted experiments that seemed to revive support for the theory.^[14] Needham boiled nutrient broths briefly to kill organisms, sealed the flasks loosely with corks, and observed microbial growth after incubation, concluding that life arose spontaneously from the broth.^[17] However, his methods were flawed, as the short boiling failed to sterilize completely, and the imperfect seals allowed airborne contamination.^[14] Italian biologist Lazzaro Spallanzani countered Needham's findings in 1765 with more rigorous tests.^[17] Spallanzani boiled broths for extended periods in sealed glass flasks, preventing any growth of organisms, and argued that Needham's results stemmed from incomplete sterilization rather than true abiogenesis.^[14] Critics, however, claimed his sealing excluded a hypothetical "vital force" from the air necessary for life to emerge.^[18] The definitive refutation arrived in 1861 through Louis Pasteur's swan-neck flask experiments.^[19] Pasteur boiled broth in flasks with elongated, curved necks that allowed air exchange but trapped dust and microbes in the bend; no growth occurred until the necks were broken, permitting contamination.^[20] This demonstrated that microbes originated from airborne particles, not spontaneous processes, effectively disproving the theory for observable life forms.^[14] In the 19th century, variants of spontaneous generation persisted among some scientists, particularly regarding microbial origins.^[21] German chemist Justus von Liebig proposed that decaying organic matter released gases through chemical processes, which then fostered the development of infusoria (microorganisms) from atmospheric elements.^[22] Liebig and contemporaries like Jöns Jacob Berzelius viewed these as natural fermentations driven by oxygen and other gases, resisting full acceptance of biogenesis until Pasteur's work.^[23] The experimental discrediting of spontaneous generation for contemporary conditions had profound philosophical implications for understanding life's origins.^[24] While it ruled out immediate emergence of visible life from decay, the concept inspired later abiogenesis theories, adapting the idea to primordial Earth environments where chemical evolution might have produced the first life forms, as in the primordial soup model.^[24]

Panspermia and Extraterrestrial Origins

Panspermia posits that life, or its precursors, originated elsewhere in the universe and was transported to Earth through interstellar mechanisms such as meteorites, comets, or radiation pressure, rather than arising solely through terrestrial processes. This hypothesis suggests that microbial life or organic compounds could survive ejection from a parent body, transit through space, and viable arrival on a new world.^[25] The concept traces back to the Greek philosopher Anaxagoras in the 5th century BCE, who proposed that "seeds of life" (panspermia) are distributed throughout the cosmos, carried by celestial bodies to generate diverse forms upon reaching suitable environments. In the modern era, the idea gained renewed attention following the Apollo missions in the late 1960s and early 1970s, which returned lunar samples and spurred interest in extraterrestrial materials potentially harboring life precursors.^[26] Key variants of panspermia include radiopanspermia, proposed by Svante Arrhenius in 1903, which envisions microscopic life forms propelled through space by stellar radiation pressure without protective shielding. Lithopanspermia extends this by suggesting that microorganisms embedded in planetary ejecta, such as rock fragments from impacts, could travel between worlds while shielded from cosmic radiation.^[27] Directed panspermia, introduced by Francis Crick and Leslie Orgel in 1973, hypothesizes intentional seeding of life by an advanced extraterrestrial civilization using spacecraft to disperse microbes or genetic material.^[28] Supporting evidence includes the discovery of complex organic molecules in meteorites, such as the Murchison carbonaceous chondrite that fell in Australia in 1969, which contains amino acids and hydrocarbons of extraterrestrial origin.^[29] Experiments have demonstrated microbial survival in space-like conditions; for instance, tardigrades exposed to the vacuum and radiation of low Earth orbit during the 2007 FOTON-M3 mission showed significant post-rehydration viability, with some specimens reproducing successfully.^[30] These findings indicate that certain extremophiles could endure interstellar travel under protective scenarios.^[31] Criticisms of panspermia center on its inability to address the ultimate origin of life, merely relocating the problem to another location, and the formidable barriers to survival during transit.^[32] Intense cosmic radiation and high-velocity impacts upon atmospheric entry would likely sterilize unprotected microbes, with models showing decay times far shorter than typical interstellar journeys.^[33] While lithopanspermia offers some shielding, the probability of ejecta escaping a planet's gravity, surviving space, and successfully landing remains low.^[34]

Formation of Habitable Conditions

Early Universe and Stellar Evolution

The Big Bang nucleosynthesis (BBN) occurred in the first few minutes after the Big Bang, approximately 13.8 billion years ago, when the universe had cooled sufficiently for protons and neutrons to combine into light atomic nuclei.^[35] During this brief period, lasting about three to twenty minutes, roughly 75% of the universe's baryonic mass formed as hydrogen-1 (protons), 25% as helium-4, with trace amounts of deuterium, helium-3, and lithium-7.^[36] These light elements—hydrogen, helium, and lithium—constituted the primordial composition of the universe, as heavier elements had not yet formed.^[37] The formation of heavier elements essential for life, such as carbon, oxygen, and nitrogen, required subsequent stellar processes. The first stars, known as Population III stars, emerged around 100 to 400 million years after the Big Bang from pristine hydrogen and helium gas clouds, lacking metals (elements heavier than helium).^[38] These massive, metal-poor stars (typically 10 to 1000 solar masses) underwent rapid nucleosynthesis in their cores, fusing hydrogen into helium and eventually producing initial quantities of carbon, oxygen, and other metals through advanced fusion stages like the carbon-oxygen cycle.^[38] Their explosive deaths as core-collapse supernovae, occurring as early as 200 million years post-Big Bang, dispersed these newly synthesized elements into the interstellar medium, enriching it for subsequent star formation.^[36] Massive stars contributed significantly to this ongoing enrichment process through helium and carbon burning in their cores, followed by explosive ejection of elements over cosmic history.^[39] The interstellar medium (ISM), comprising diffuse gas and dust clouds between stars, served as a reservoir for these enriched materials, facilitating the accumulation of organic molecules. Dust grains in molecular clouds absorbed and catalyzed the formation of complex organics from simpler precursors like carbon monoxide and methanol, with over 250 molecular species identified to date, including prebiotic compounds.^[40] The first detectable metals in the universe appeared around 13.2 billion years ago, corresponding to redshifts of z ≈ 10–20, marking the transition from a metal-free era to one where stellar ejecta began seeding planetary systems with life-essential elements.^[41]

Earth's Accretion and Geological Priming

The formation of Earth began approximately 4.6 billion years ago through the gravitational collapse of a portion of the solar nebula, a vast cloud of gas and dust surrounding the young Sun, which flattened into a protoplanetary disk where planetesimals accreted to form the planet.^[42] This process involved the aggregation of rocky and metallic materials, primarily derived from heavier elements forged in previous stellar nucleosynthesis, leading to Earth's differentiation into a core, mantle, and crust over millions of years.^[43] By around 4.54 billion years ago, Earth had reached its current mass, setting the stage for subsequent geological developments essential for chemical complexity.^[44] During the Hadean eon, spanning from Earth's formation to about 4 billion years ago, the planet experienced intense dynamical events that shaped its structure. A cataclysmic collision with a Mars-sized protoplanet named Theia approximately 4.5 billion years ago ejected debris that coalesced to form the Moon, while also tilting Earth's axis and contributing to its rapid spin, which influenced early atmospheric retention.^[45] This was followed by the Late Heavy Bombardment, a period of heightened meteoritic impacts from roughly 4.1 to 3.8 billion years ago, driven by orbital instabilities in the outer Solar System, which resurfaced the planet and delivered volatiles but also repeatedly sterilized its surface.^[46] Earth's early atmosphere evolved through the loss of primordial hydrogen and helium gases, accreted from the solar nebula, due to the planet's insufficient gravity and high temperatures, followed by secondary outgassing from volcanic activity that released carbon dioxide (CO₂), nitrogen (N₂), and water vapor (H₂O) as dominant components.^[47] This volcanic degassing, occurring primarily during the Hadean, created a dense, greenhouse-laden atmosphere that trapped heat and facilitated the cycling of essential volatiles.^[48] Over time, interactions with the surface, including photodissociation and potential cometary additions, began to modify its composition toward one more conducive to aqueous chemistry.^[49] The planet's initially molten surface, resulting from accretion heat and radiogenic decay, gradually cooled, allowing the formation of a solid crust and the condensation of water into oceans by at least 4.4 billion years ago, as evidenced by oxygen isotope ratios in ancient detrital zircons from Western Australia's Jack Hills.^[50] These zircons, preserved metamorphic minerals, indicate the presence of liquid water and granitic crust formation much earlier than previously thought, suggesting a relatively rapid transition from a magma ocean to habitable surface conditions.^[51] Key geological processes further primed Earth for chemical evolution, including the initiation of plate tectonics, which evidence from ancient crystals suggests began over 4.2 billion years ago, recycling crust and concentrating minerals at convergent boundaries to foster geochemical gradients.^[52] Concurrently, the emergence of Earth's magnetic field, generated by dynamo action in the liquid outer core and dated to at least 3.7 billion years ago through paleomagnetic records in rocks, provided crucial shielding against solar wind and cosmic radiation, preventing atmospheric stripping and enabling stable surface environments.^[53] This geodynamo, sustained by core convection, thus played a protective role in maintaining volatile inventories essential for prebiotic processes.^[54]

Timeline of Pre-Life Earth

The formation of Earth occurred approximately 4.54 billion years ago through the accretion of planetesimals in the solar nebula, marking the initial stage of planetary development. Between 4.6 and 4.4 billion years ago, the planet underwent intense heating from impacts and radioactive decay, leading to differentiation into core, mantle, and crust, while surface cooling facilitated the condensation of a primitive ocean. Evidence for this early ocean formation comes from detrital zircons in the Jack Hills of Western Australia, dated to as old as 4.4 billion years, which exhibit oxygen isotope ratios indicative of interaction with liquid water under surface conditions.^[55]^[56] From 4.4 to 4.0 billion years ago, Earth's atmosphere was likely dominated by carbon dioxide and nitrogen, with water vapor, forming a weakly reducing or neutral composition influenced by volcanic outgassing and loss of lighter gases to space; the exact degree of reducing components like hydrogen or methane remains debated, with some models suggesting transient reducing conditions from impacts that could have supported prebiotic organic synthesis.^[57]^[58]^[59] The interval of 3.8 to 3.5 billion years ago saw the conclusion of the Late Heavy Bombardment, a spike in asteroid and comet impacts that peaked around 4.1 to 3.8 billion years ago and tapered off by approximately 3.8 billion years ago, allowing for more stable surface conditions. Concurrently, the emergence of stable continental crust became evident, with the oldest preserved fragments dating to about 4.0 billion years ago, but more extensive development by 3.5 billion years ago providing sialic platforms that enhanced geochemical cycling and habitability.^[46]^[60] Potential biomarkers from this era include controversial 3.7 billion-year-old graphite inclusions within metasedimentary rocks of the Isua Supracrustal Belt in Greenland, where the graphite shows carbon isotope compositions depleted in ¹³C (δ¹³C values around -20‰ to -30‰) relative to inorganic carbon, suggesting a biogenic origin from microbial metabolism. However, debates persist regarding metamorphic overprinting and abiotic formation mechanisms, underscoring the need for further verification.^[61] By approximately 3.5 billion years ago, the transition from abiotic to biotic processes is marked by the appearance of stromatolites—layered sedimentary structures formed by microbial mats—in the Pilbara Craton of Western Australia, representing the earliest undisputed evidence of photosynthetic life and the onset of biological influence on Earth's geology.^[62]^[63]

Prebiotic Molecular Synthesis

Extraterrestrial Organic Contributions

Extraterrestrial sources have provided key organic molecules that could serve as prebiotic feedstocks for abiogenesis on early Earth, including amino acids, sugars, and nucleobases detected in meteorites, comets, and interstellar media. These compounds, formed through processes like gas-phase reactions, UV photolysis, and ice chemistry in space, demonstrate the potential for cosmic delivery of life's building blocks. Observations from missions and telescopes reveal a diverse inventory of organics, suggesting that impacts during Earth's formative period transported substantial quantities to the surface, supplementing endogenous synthesis. Meteorites, particularly carbonaceous chondrites, contain a variety of amino acids that predate terrestrial biology. The Murchison meteorite, which fell in Australia in 1969, yielded over 70 amino acids upon analysis, including 8 proteinogenic types and many non-terrestrial isomers, confirmed as extraterrestrial through isotopic signatures. Samples from the Ryugu asteroid, returned by Japan's Hayabusa2 mission in 2020, include nucleobases such as uracil, a component of RNA, alongside other nitrogenous organics, indicating synthesis in the early solar system.^[64] Comets also deliver simple organics, with the Rosetta mission detecting glycine—the simplest amino acid—in the coma of comet 67P/Churyumov-Gerasimenko in 2016, alongside phosphorus-bearing species.^[65] The same mission identified abundant formaldehyde (HCHO) and methanol (CH3OH), precursors to more complex sugars, in the comet's dust and gas, with abundances suggesting formation in the interstellar medium or protosolar disk. Radio astronomy has revealed organics in interstellar clouds, such as glycolaldehyde (CH2OHCHO)—the simplest sugar—in the Sagittarius B2 molecular cloud, detected via millimeter-wave spectroscopy. This compound, observed in emission lines toward the Galactic center, points to gas-grain chemistry producing prebiotic molecules far from the solar system. Delivery occurred primarily through impacts, with the Late Heavy Bombardment (approximately 4.1–3.8 billion years ago) estimated to have supplied around 10^{20} kg of organic matter to Earth, based on models of cometary and asteroidal flux. Modern influx from meteorites and interplanetary dust particles adds roughly 10^5–10^6 kg of organics annually, a rate that was orders of magnitude higher during the early Hadean eon due to elevated bombardment. These deliveries likely enriched prebiotic environments, providing diverse carbon and nitrogen sources for molecular assembly.

Terrestrial Laboratory Simulations

Terrestrial laboratory simulations of abiogenesis seek to replicate plausible early Earth conditions to synthesize organic compounds from inorganic precursors, providing empirical support for prebiotic chemistry pathways. These experiments typically involve controlled environments that mimic atmospheric, aqueous, or geological processes, such as electrical discharges, radiation, or high-pressure reactions, to drive the formation of biomolecules like amino acids and nucleotides. By varying parameters like gas composition, energy sources, and temperature, researchers test hypotheses about the chemical evolution on a young planet.^[5] The seminal Miller-Urey experiment, conducted in 1953, utilized a glass apparatus to simulate a reducing primitive atmosphere composed of methane (CH₄), ammonia (NH₃), hydrogen (H₂), and water vapor (H₂O). A spark discharge mimicked lightning, heating the mixture to evaporate water and cycle gases through the system for one week, resulting in the production of several amino acids, including glycine, alanine, and aspartic acid, with a total conversion yield of approximately 15% of the starting carbon into organic compounds. This setup demonstrated that simple inorganic gases could yield building blocks of proteins under energized conditions, marking a foundational validation of the Oparin-Haldane hypothesis that life's precursors arose in a primordial soup.^[5]^[66] Subsequent variants have refined these methods to account for revised models of early Earth's atmosphere and geology. Reanalyses of archived samples from experiments simulating volcanic conditions, such as the 2008 study by Johnson et al., identified 22 amino acids at yields comparable to the classic setup but with enhanced diversity due to sulfur-containing intermediates like H₂S, CO₂, and N₂ alongside water vapor. These adaptations highlight how localized volcanic activity could have concentrated reactive species in prebiotic settings.^[67] A 2011 reanalysis of a 1958 H₂S-rich spark discharge experiment by Bada et al. further expanded findings to over 20 amino acids, including sulfur-containing ones like methionine.^[68] Beyond electrical discharges, other laboratory setups explore alternative energy sources and environments. Ultraviolet (UV) irradiation experiments on frozen mixtures of water (H₂O) and methane (CH₄) at low temperatures (around 10-77 K) simulate irradiation of icy surfaces, yielding complex organics such as alcohols, aldehydes, and carboxylic acids through photolysis and radical recombination. Hydrothermal reactor experiments, conducted under high pressure (up to 200 atm) and temperature (150-300°C) to mimic deep-sea vents, use flow-through systems with minerals like iron sulfides to catalyze organic synthesis from CO₂ and H₂, producing formate, acetate, and pyruvate as key intermediates. These approaches underscore the role of diverse energy gradients in driving prebiotic reactions.^[69]^[70] Despite successes, these simulations reveal limitations in yield and specificity. Amino acid production is efficient in spark and UV setups, often reaching millimolar concentrations, but sugar synthesis remains low-efficiency, with yields below 1% due to instability under reducing conditions. Such constraints emphasize the need for complementary mechanisms, like mineral catalysis, to accumulate sufficient biomolecule concentrations, while collectively affirming the feasibility of abiotic organic formation as posited by Oparin and Haldane.^[67]^[66] Recent advances in the 2020s have incorporated plasma-based simulations to probe hydrogen cyanide (HCN) polymerization, a proposed route to nucleobase precursors. Non-thermal plasma discharges in N₂-CH₄-H₂O mixtures generate HCN at high rates (up to 10⁻⁵ mol/L/h), which then polymerize into imino-polymers containing adenine-like structures under mild aqueous conditions. These experiments, using dielectric barrier discharges to emulate auroral or lightning plasmas, achieve polymerization degrees of 10-50 units, offering insights into rapid prebiotic network formation on early Earth. In 2025, a community-curated database was introduced to catalog prebiotic reactions, aiding systematic exploration of chemical networks.^[71] Additionally, studies highlighted the role of N-O bond-containing compounds as key intermediates in prebiotic synthesis.^[72]^[73]

Synthesis of Core Biomolecules

The synthesis of amino acids under prebiotic conditions is exemplified by the Strecker synthesis, in which hydrogen cyanide (HCN), aldehydes, and ammonia (NH₃) react to form α-amino acids such as glycine and alanine.^[74] This pathway proceeds via the formation of an α-aminonitrile intermediate, followed by hydrolysis, and is considered plausible on early Earth due to the availability of these precursors in reducing atmospheres or hydrothermal settings.^[75] Yields can reach several percent under mild aqueous conditions, supporting the accumulation of proteinogenic monomers.^[76] Sugars essential for nucleic acids, particularly ribose, can form through the formose reaction, where formaldehyde polymerizes in the presence of a base catalyst to produce a mixture of aldoses including ribose.^[77] However, this process yields low concentrations of ribose—typically less than 1%—and results in a racemic mixture alongside numerous side products, posing challenges for selective prebiotic accumulation.^[78] To address these limitations, mineral-catalyzed alternatives have been proposed, such as borate stabilization, which complexes with ribose to enhance its yield and prevent degradation during formose-like reactions. Nucleobases, the building blocks of genetic polymers, arise from HCN oligomerization pathways. Adenine, for instance, forms through the polymerization of HCN in ammoniacal solutions, yielding up to 0.5% under heating at 70–90°C for several days, mimicking primitive Earth conditions. Complementary routes to pyrimidine precursors include the prebiotic synthesis of orotic acid, a key intermediate toward uracil and cytosine, via reactions of α-ketoacids with cyanide and ammonia, paralleling modern biosynthetic steps and achieving yields of several percent in one-pot setups.^[79] Lipids capable of forming membranes are produced via Fischer-Tropsch-type (FTT) synthesis in hydrothermal environments, where carbon monoxide (CO) and hydrogen (H₂) react over catalytic mineral surfaces like iron sulfides to generate amphiphilic hydrocarbons and fatty acids. These processes, occurring at temperatures of 100–250°C and pressures relevant to deep-sea vents, yield linear and branched chain lengths suitable for vesicle formation, with distributions peaking at C₁₀–C₁₈.^[80] Polymerization of these monomers into biopolymers, such as peptides from amino acids, occurs through dehydration mechanisms facilitated by wet-dry cycles on mineral surfaces. In such cycles, amino acids condense during drying phases at moderate temperatures (around 85°C), with copper ions or clays enhancing rates to form di- to oligopeptides, though overall yields remain low (often <10% for chains beyond trimers) due to hydrolysis in wet phases and racemization issues. Stability challenges persist, as longer peptides hydrolyze rapidly in aqueous prebiotic soups, limiting accumulation without protective environments.

Assembly of Protocellular Structures

Membrane Formation and Vesicles

Amphiphilic molecules, particularly fatty acids with chain lengths of 8 to 12 carbons such as decanoic acid, play a central role in the formation of primitive membranes during abiogenesis by self-assembling into bilayer structures under prebiotic conditions. These molecules possess a hydrophilic carboxylic acid head and a hydrophobic hydrocarbon tail, enabling spontaneous organization in aqueous environments. At pH values between 7 and 9, near or slightly above their effective pKa (typically 5–7 for short-chain fatty acids), the deprotonated carboxylate forms ionic interactions that stabilize bilayers, while at lower pH values below the pKa, protonation leads to the formation of neutral acids that assemble into monolayers or oil-like phases rather than stable bilayers.^[81]^[82] The resulting vesicles from these fatty acid bilayers exhibit key properties suitable for protocellular boundaries, with typical diameters ranging from 100 to 500 nm, forming small unilamellar structures that encapsulate aqueous contents. Unlike modern phospholipid membranes, these primitive vesicles demonstrate high permeability to ions, small organic molecules, and nutrients such as nucleotides, allowing passive diffusion essential for early metabolic processes without requiring complex transport proteins.^[81]^[83] Prebiotic sources for these membrane-forming fatty acids include extraterrestrial delivery via carbonaceous meteorites, which contain straight-chain fatty acids with 8 to 18 carbon atoms, as identified in the Murchison meteorite. Terrestrial synthesis during serpentinization of ultramafic rocks in hydrothermal systems could also produce such amphiphiles through Fischer-Tropsch-type reactions, yielding linear fatty acids from CO2, H2, and mineral catalysts. Recent experiments have demonstrated the self-assembly of membranous protocells on micrometeorites, supporting extraterrestrial delivery as a prebiotic mechanism.^[84]^[83]^[82] These vesicles demonstrate dynamic stability relevant to early Earth conditions, growing through the insertion of free fatty acid monomers from the surrounding solution into the bilayer, which increases surface area and volume while maintaining osmotic balance. Division occurs naturally under mechanical shear forces, such as those from fluid convection, wave action, or agitation, which deform and fission the vesicles into smaller daughter structures.^[85] Experimental evidence supports the role of mineral surfaces in facilitating vesicle formation and functionality; montmorillonite clay catalyzes the rapid conversion of fatty acid micelles into stable vesicles and promotes the encapsulation of macromolecules or particles within them, mimicking primitive compartmentalization in clay-rich prebiotic environments.

Compartmentalization and Primitive Metabolism

Compartmentalization in protocells enabled the concentration of prebiotic molecules, facilitating chemical reactions that would be inefficient in dilute solutions. Osmotic gradients across primitive vesicle membranes, formed by fatty acids such as oleic acid, drove the uptake of additional membrane components, thereby increasing vesicle volume and concentrating internal solutes like RNA oligomers.^[86] Clay minerals, particularly montmorillonite, played a complementary role by adsorbing nucleotides and amino acids through electrostatic interactions between their charged surfaces and the molecules' phosphate or carboxylate groups, achieving concentration factors of up to several orders of magnitude under prebiotic conditions.^[87] This adsorption not only protected molecules from hydrolysis but also positioned them for polymerization, as demonstrated in experiments where montmorillonite catalyzed the formation of RNA oligomers from activated monomers.^[88] Within these compartments, primitive metabolic cycles could be sustained, providing a framework for carbon fixation and energy transfer. Non-enzymatic analogs of the acetyl-CoA pathway, involving reactions of carbon monoxide, methyl groups, and CoA-like thiols, have been proposed to produce acetate and pyruvate precursors, mimicking early autotrophy.^[89] Similarly, the reverse citric acid cycle (rTCA), a reductive pathway for assimilating CO₂ into organic acids like oxaloacetate and α-ketoglutarate, is proposed as a core primitive metabolism that could operate autocatalytically in enclosed spaces, with iron-sulfur minerals enhancing key reductive steps.^[89] Encapsulation in vesicles would concentrate intermediates, reducing side reactions and allowing cycle completion, as evidenced by geochemical models integrating rTCA with hydrothermal inputs. Experimental models demonstrate that protocells achieved encapsulation efficiencies of 10–20% for RNA oligomers during vesicle formation, allowing sufficient internal concentrations for sustained chemistry.^[90] These vesicles exhibit a growth-division cycle, where osmotic swelling from encapsulated solutes doubles the volume, followed by mechanical or chemical splitting that distributes contents into daughter vesicles, enabling rudimentary proliferation.^[90] However, primitive compartments faced challenges such as membrane leakiness, where fatty acid bilayers permitted passive diffusion of small molecules and ions, potentially diluting metabolic products. Additionally, establishing stable proton gradients across these permeable membranes was essential for driving primitive cycles but remained difficult without specialized transporters, limiting the efficiency of early metabolic processes.

Development of Biological Processes

Energy Gradients and Chemiosmosis

In the context of abiogenesis, thermodynamic principles govern the feasibility of prebiotic reactions by dictating that spontaneous processes must increase the overall entropy of the universe, as per the second law of thermodynamics.^[91] While isolated systems tend toward maximum entropy, open systems on early Earth—such as geochemical environments—could sustain local order through energy dissipation, where free energy changes (ΔG) arise from chemical disequilibria, expressed as ΔG = RT ln (Q/K) under non-equilibrium conditions that drive synthesis when Q < K. These disequilibria, including redox and pH gradients, provided the thermodynamic impetus for forming complex molecules from simpler precursors without violating entropy constraints.^[92] A pivotal framework for understanding energy transduction in early life is the chemiosmotic theory, proposed by Peter Mitchell in 1961, which posits that proton gradients across membranes generate a proton motive force (Δp) to drive ATP synthesis. This force is quantified as:

\Delta p = \Delta \psi - \frac{2.3 RT}{F} \Delta \mathrm{pH}

where Δψ is the membrane potential, ΔpH is the pH difference, R is the gas constant, T is temperature, and F is the Faraday constant; this electrochemical gradient powers ATP production via the F₀F₁-ATPase enzyme in modern cells. In prebiotic scenarios, analogous proton gradients could have emerged naturally, harnessing geochemical energy without enzymatic machinery. Prebiotic analogs of these gradients include H₂/CO₂ disequilibria in alkaline hydrothermal vents, where pH differences across iron-sulfide barriers (up to 3–4 units) drive vectorial electrochemistry for CO₂ reduction to organics, mimicking chemiosmotic coupling. Similarly, UV-driven electron transfer in surface waters could generate transient redox gradients; for instance, far-UV photolysis of H₂O and CO₂ produces solvated electrons that reduce simple molecules like HCN, facilitating abiotic synthesis of amino acids and nucleobases under early Earth's intense solar radiation.^[93] These mechanisms highlight how environmental energy gradients could have powered primitive metabolic cycles. Entropy plays a dual role in abiogenesis: compartments such as mineral pores or lipid vesicles enable local entropy decreases by concentrating reactants and products, fostering ordered chemical networks, while overall entropy increases through heat dissipation to the surroundings.^[92] This dissipative structuring aligns with non-equilibrium thermodynamics, where far-from-equilibrium systems self-organize to maximize entropy production.^[91] For ATP synthesis, prebiotic versions may have relied on peptide-assisted analogs rather than full F₀F₁-ATPase; histidyl-rich peptides, formed abiotically, catalyze phosphate transfer from ATP-like imidazolium phosphates, generating energy equivalents under mild conditions plausible for early Earth. A 2025 study showed that fatty acid-based protocells can sustain proton gradients to drive ATP synthesis via ATP synthase analogs under simulated vent conditions.^[94]^[95] This suggests a gradual evolution from geochemical proton gradients to peptide-mediated energy capture, bridging abiotic chemistry to proto-metabolism.^[96]

RNA World and Genetic Replication

The RNA world hypothesis proposes that early life on Earth relied on RNA molecules to fulfill both genetic storage and catalytic functions, prior to the evolution of DNA as the primary genetic material and proteins as specialized enzymes. This scenario, articulated by Walter Gilbert in 1986, envisions a primordial stage where self-replicating RNA systems drove the basic processes of life, bridging the gap between simple organic chemistry and complex cellular biology.^[97] The hypothesis gained traction as it addressed the "chicken-and-egg" problem of interdependent DNA, RNA, and proteins, suggesting RNA's versatility allowed it to bootstrap biological complexity without requiring modern macromolecules.^[98] Key evidence supporting the RNA world comes from the discovery of ribozymes—RNA molecules with enzymatic activity. In 1982, Thomas Cech and colleagues identified the first ribozyme in the self-splicing Group I intron of Tetrahymena ribosomal RNA, where the RNA catalyzes its own excision from a precursor transcript without protein assistance. Further bolstering this view, structural studies of the ribosome reveal that its peptidyl transferase center, responsible for peptide bond formation in protein synthesis, is composed entirely of ribosomal RNA, indicating an ancient RNA-based catalytic core that predates protein involvement. Prebiotic synthesis of RNA faces significant challenges, particularly in forming stable nucleotides and phosphodiester linkages under plausible early Earth conditions. Matthew Powner and colleagues demonstrated in 2009 that activated pyrimidine ribonucleotides could form via a pathway involving cyanamide and glycolaldehyde, bypassing the unstable free ribose sugar and avoiding the need for separate nucleobase assembly.^[99] Additionally, wet-dry cycles in evaporating pools can promote the formation of RNA-like polymers with 2'-5' phosphodiester linkages from cyclic nucleotides, yielding oligomers up to 30 units long, though these non-standard bonds highlight the need for subsequent isomerization to 3'-5' linkages for functional RNA.^[100] Energy for such polymerization could derive from environmental gradients, as explored in prior contexts of protocell assembly. For replication, template-directed polymerization of RNA monomers has been achieved non-enzymatically on mineral surfaces like montmorillonite clay, which adsorbs nucleotides and catalyzes the formation of oligomers up to 50 units in length by aligning them for stepwise addition. These processes exhibit high error rates, approximately 1 in 10^2 nucleotides incorporated, limiting initial replicator fidelity but allowing for rapid sequence variation essential for evolutionary exploration. Over time, such RNA replicators could evolve toward Darwinian selection, where heritable variations in replication efficiency or catalytic function confer advantages, leading to diversification and complexity in a competitive molecular environment—as evidenced by in vitro experiments showing emergent RNA networks undergoing serial transfer evolution. Recent experiments, such as a 2024 study at the Salk Institute showing an RNA polymerase ribozyme that accurately copies other RNA strands, provide evidence for non-enzymatic replication. Additionally, a 2025 model proposes a stepwise transition from autocatalytic to template-based RNA replication.^[101]^[102]^[103]

Protein Synthesis and Early Enzymes

The origins of the ribosome are traced to an RNA-dominated era, where ribosomal RNA (rRNA) functioned as the core peptidyl transferase enzyme, catalyzing peptide bond formation without reliance on proteins.^[104] This ribozyme activity, conserved across modern ribosomes, suggests that early translation machinery emerged from RNA scaffolds capable of linking amino acids into short polypeptides, potentially enhancing catalytic efficiency beyond standalone RNA molecules.^[105] Small peptides likely assisted in stabilizing rRNA folding, acting as primitive chaperones to facilitate the assembly of functional ribosomal structures in prebiotic conditions.^[106] The development of translation machinery involved the emergence of transfer RNA (tRNA) as adaptors that bridged nucleotide sequences with amino acids, enabling more precise aminoacylation. A 2025 experiment showed that amino acids can spontaneously attach to RNA via thioesters in prebiotic conditions, suggesting an early mechanism for non-coded aminoacylation.^[107]^[108] Codon assignments, initially ambiguous, evolved through stereochemical affinities between anticodons and amino acids, gradually refining the genetic code to support 20 standard amino acids via triplet codons.^[109] These tRNAs, derived from self-folding RNA hairpins, integrated with ribosomal RNA templates to direct non-random peptide synthesis, marking a transition from stochastic polymerization to information-directed protein formation. Early peptides exhibited functional capabilities, such as forming beta-sheet structures that promoted hydrolysis of phosphate bonds or stabilized RNA interactions, providing selective advantages in prebiotic environments.^[110] These short chains, synthesized on RNA templates, could catalyze reactions like ester hydrolysis, compensating for the limitations of RNA catalysis and fostering metabolic versatility.^[110] The coevolution of RNA and proteins featured RNA chaperones that enhanced protein stability by preventing aggregation, while peptides in turn protected RNA from degradation, creating interdependent systems.^[106] This mutualism extended to reverse translation influences, where peptide sequences modulated RNA folding, accelerating the integration of coded synthesis.^[111] Key milestones in protein synthesis occurred around 3.8 billion years ago, evolving from random amino acid polymers to ribosome-mediated, codon-directed assembly that underpinned the diversification of enzymatic functions.^[106]

Emergence of the Last Universal Common Ancestor

The Last Universal Common Ancestor (LUCA) is the hypothesized progenitor of all extant cellular life on Earth, marking the point from which the domains Bacteria, Archaea, and Eukarya diverged through Darwinian evolution.^[112] This entity is inferred to have existed as a prokaryote-like cell approximately 4.2 billion years ago, during the early Hadean eon, based on Bayesian phylogenetic dating that integrates microbial fossil records, geological constraints, and molecular clock analyses.^[113] LUCA possessed a rudimentary cellular structure, including a lipid membrane for compartmentalization, a DNA-based genome, RNA components for information processing, and proteins for catalysis and structure, enabling the transition from prebiotic chemistry to heritable replication.^[114] Genomic reconstructions of LUCA rely on identifying orthologous protein families conserved across diverse prokaryotic genomes, revealing a core set of essential genes shared by all domains of life. The 2024 analysis estimates LUCA’s genome encoded approximately 2,657 proteins (95% HPD: 2,451–2,855), including those for translation, replication, and basic metabolism, indicating a more complex organism than earlier minimal models, with a genome size of about 2.75 Mb.^[113] Additionally, the presence of reverse gyrase genes indicates thermophilic adaptations, suggesting LUCA thrived in high-temperature environments.^[114] Metabolic inferences portray LUCA as an anaerobic chemolithoautotroph, deriving energy from hydrogen oxidation and fixing carbon dioxide via the Wood–Ljungdahl pathway, a reversible acetyl-CoA synthesis route still found in modern acetogens and methanogens.^[114]^[113] This pathway, involving enzymes like formylmethanofuran dehydrogenase and carbon monoxide dehydrogenase, would have allowed carbon assimilation without oxygen, consistent with an anoxic early Earth atmosphere.^[114] Nitrogen metabolism likely included nitrogenase for fixation, further supporting autotrophy.^[114] In the tree of life, LUCA occupies the root, with its descendants branching into Bacteria (e.g., basal Clostridia-like lineages) and the Archaea-Eukarya clade (e.g., methanogen-like archaea), as determined by rooted phylogenies using ancient duplicated genes and outgroup comparisons.^[114]^[113] Debates persist on LUCA's complexity: while early models envisioned a minimal genome with few genes, reconstructions like Weiss et al. (2016) argue for a more sophisticated organism with a genome size comparable to modern prokaryotes (~2.5 Mb), diverse transporters, and integrated metabolic networks, challenging simplistic origins and implying prior evolutionary refinement; recent 2024 analyses reinforce this with even larger gene counts.^[114]^[113]

Environmental Contexts for Abiogenesis

Deep-Sea Hydrothermal Systems

Deep-sea hydrothermal systems, particularly alkaline vents formed through serpentinization of ultramafic rocks along mid-ocean ridges, provide a geochemical setting conducive to abiogenesis at depths of approximately 800 meters, with fluid temperatures ranging from 40°C to 91°C, as exemplified by the Lost City Hydrothermal Field on the Atlantis Massif.^[115] These environments feature porous carbonate chimneys that facilitate fluid circulation and mineral interactions, creating localized niches for prebiotic chemistry under high hydrostatic pressure.^[116] Unlike high-temperature black smoker vents, alkaline systems like Lost City maintain milder conditions that could sustain delicate organic molecules.^[117] The chemistry of these systems centers on serpentinization, where olivine and pyroxene in the mantle react with seawater to produce hydrogen gas (H₂) through oxidation of ferrous iron to magnetite, alongside formation of serpentine minerals.^[117] This H₂ can react with carbon dioxide (CO₂) from the fluids or ocean to generate simple organics via Fischer-Tropsch-type synthesis, with iron-sulfide (FeS) minerals acting as catalysts to promote carbon fixation and reduction reactions.^[118] In Lost City fluids, H₂ concentrations reach millimolar levels, enabling abiotic methane production and providing a reducing environment rich in energy sources for emerging metabolic pathways.^[117] A key feature is the natural proton gradient across thin inorganic barriers in the vent structures, where alkaline fluids (pH 9–11) emerge into the mildly acidic Hadean ocean (pH ~5–7), creating a ΔpH of 2–3 units that could drive primitive chemiosmosis without biological membranes.^[119] This electrochemical disequilibrium, combined with thermal and redox gradients, mimics the proton motive force essential for early energy transduction, as proposed in the alkaline vent hypothesis.^[120] Experimental simulations support these vents as sites for protocell assembly, notably through Nick Lane and Michael Russell's "iron-sulfur world" hypothesis, which posits that life originated within FeS compartments at seepage-site mounds, harnessing H₂ and CO₂ for acetyl-CoA pathway precursors.^[120] Further, laboratory recreations of vent conditions at 160–260°C demonstrate rapid peptide bond formation from glycine, with exergonic shifts favoring oligopeptide elongation at rates up to 0.12 mM per hour, enhanced by mineral surfaces and fluid cycling.^[121] Modern analogs at Lost City reveal dense microbial mats dominated by chemolithoautotrophic archaea and bacteria, such as Methanosarcina-like methanogens and sulfate-reducing Deltaproteobacteria, thriving on H₂ oxidation and demonstrating a complete sulfur cycle that echoes potential early Earth ecosystems. These mats, forming on chimney surfaces, highlight sustained biological activity in alkaline, H₂-rich settings.

Surface Aqueous Environments

Surface aqueous environments on early Earth, such as shallow pools and ponds, have been proposed as key sites for abiogenesis due to their potential to concentrate prebiotic organics through wet-dry cycles. In these settings, evaporation in shallow pools would drive dehydration reactions, promoting the polymerization of monomers into more complex molecules like peptides and nucleic acids, while subsequent wetting disperses protocells for further evolution.^[122] Experimental simulations demonstrate that repeated wet-dry cycles in primordial soup-like conditions can accumulate and concentrate organic compounds from atmospheric or extraterrestrial sources, facilitating the formation of protocell precursors.^[122] Hot springs, analogous to those in modern Yellowstone, provided moderate temperatures of 50–90°C suitable for prebiotic chemistry, where geothermal heat and mineral-rich waters supported organic synthesis. Silica gels formed in these environments aided polymerization by providing catalytic surfaces that trapped and concentrated monomers during wet-dry fluctuations, enhancing reaction rates for RNA-like polymers.^[123] These silica structures also offered protection against UV degradation, preserving delicate biomolecules in shallow pool margins.^[124] Temperate pools, evoking Charles Darwin's 1871 vision of a "warm little pond" with ammonia, phosphoric salts, light, heat, and electricity enabling protein formation, allowed evaporative processes to drive nucleotide synthesis. In such settings, cyclic evaporation concentrates precursors like sugars and bases, yielding pyrimidine nucleotides through dehydration-condensation reactions without requiring harsh conditions.^[125] Icy surface environments, serving as analogs for extraterrestrial bodies like Europa, utilized freeze-concentration in eutectic phases to accelerate prebiotic reactions such as the formose reaction, which produces sugars from formaldehyde. Freezing excludes solutes into concentrated liquid pockets within ice, increasing reactant proximity and enabling aldose synthesis under low temperatures that inhibit degradation.^[126] These surface aqueous sites offered advantages including direct access to atmospheric gases for carbon and nitrogen inputs, as well as tidal and wave energy for mixing nutrients without dilution.^[122]

Subsurface and Extraterrestrial Settings

In the continental crust of early Earth, pores and fractures at depths of 100–1000 meters provided shielded microenvironments conducive to prebiotic chemistry. These subsurface spaces, formed by tectonic activity, hosted supercritical fluids rich in CO₂ and N₂, enabling the concentration and polymerization of organic molecules into protocell-like vesicles.^[127] Radiolysis of water by naturally occurring radioactive elements, such as uranium and thorium, generated molecular hydrogen (H₂) as an energy source, supporting reducing conditions essential for synthesizing complex organics. Clay minerals, abundant in these fractures, acted as catalysts by adsorbing and aligning monomers like nucleotides, facilitating their linkage into RNA oligomers and promoting the formation of primitive genetic systems.^[127] This catalytic role of clays, including montmorillonite and illite, mirrors laboratory simulations where mineral surfaces enhance polymerization under hydrated, low-temperature conditions. Evidence for such subsurface prebiotic processes draws from the modern deep biosphere, where microbes thrive in granite-hosted fractures up to several kilometers deep, utilizing radiolytic H₂ for metabolism. These microbial communities, comprising up to 90% of Earth's bacterial and archaeal biomass, demonstrate the long-term habitability of crustal pores and suggest that similar niches could have incubated early life. Prebiotic reactions in granite fractures have been replicated experimentally, showing the synthesis of amino acids, nucleobases, and even purine-pyrimidine nucleosides from formamide precursors under hydrothermal-like conditions, highlighting the crust's potential as a site for abiogenic organic assembly. As proposed by Mulkidjanian et al., continental geothermal fields with clay-rich subsurface layers offered anoxic, potassium- and phosphate-enriched settings that aligned with cellular ion requirements, favoring the emergence of membrane-bound protocells over oceanic origins.^[128] Extraterrestrial settings extend these subsurface concepts to icy moons, where analogous protected environments may foster abiogenesis. On Enceladus, a moon of Saturn, Cassini spacecraft observations in 2015 detected H₂ in water-rich plumes erupting from subsurface oceans, indicating active hydrothermal activity at the rocky core that could provide energy for prebiotic synthesis akin to Earth's radiolytic processes.^[129] Similarly, Titan's thick atmosphere produces tholins—complex organic aerosols that settle into surface lakes and subsurface layers—yielding amino acids upon hydrolysis, as shown in laboratory analogs simulating low-temperature aqueous interactions. These tholins, rich in nitrogen and carbon, represent a prebiotic feedstock potentially driving polymerization in shielded, cryogenic pores. Subsurface venues offer key advantages for abiogenesis, including natural radiation shielding from cosmic rays and UV light by overlying rock or ice, which preserves delicate biomolecules, and stable, moderate temperatures (typically 20–100°C on Earth, or -180°C to 0°C on icy moons) that prevent thermal degradation while allowing sustained reactions.^[130] Hybrid models integrate these sites with surface environments through geochemical exchange, such as plume ejection on Enceladus or groundwater upwelling on early Earth, potentially delivering surface-synthesized organics to protected depths for further evolution.^[131]

Key Challenges

Homochirality in Biomolecules

Homochirality refers to the exclusive use of one enantiomer in biological macromolecules, such as L-amino acids in proteins and D-sugars in nucleic acids, which is essential for efficient biochemical function.^[132] Racemic mixtures, containing equal amounts of both enantiomers, inhibit polymerization processes critical for forming biopolymers like peptides and oligonucleotides, as the opposing handedness disrupts ordered chain elongation. Achieving an enantiomeric excess (ee), defined as the percentage difference between the major and minor enantiomers (([L] - [D])/([L] + [D]) × 100%), greater than 99% is necessary for viable prebiotic synthesis, as lower excesses lead to inefficient or stalled reactions; for instance, the eutectic phase of serine allows near-homochiral solutions only at such high ee levels.^[132] Several mechanisms have been proposed to generate initial chiral asymmetries in prebiotic environments. Astrophysical sources, such as circularly polarized ultraviolet light from star-forming regions, can preferentially photolyze one enantiomer of amino acids in interstellar ices or dust grains, producing ee values up to ~2% for alanine and higher (up to ~17%) for other species like isovaline.^[133] On Earth, geochemical processes involving mineral surfaces may induce ee through selective adsorption or catalysis; for example, chiral faces of calcite crystals have been shown to enrich one enantiomer of amino acids by up to ~10-20% during adsorption from solution, while clays like montmorillonite can template asymmetric polymerization with modest ee biases.^[134] Additionally, Viedma ripening—a process of attrition-enhanced crystallization in slurries of racemic compounds—can amplify near-zero ee to complete homochirality under grinding conditions mimicking hydrothermal agitation, as demonstrated with sodium chlorate and applied to prebiotic models like amino acid derivatives. Extraterrestrial delivery via meteorites provides evidence of pre-solar chiral excesses that could seed Earth's oceans. The Murchison meteorite, a carbonaceous chondrite, contains amino acids with small L-enantiomeric excesses, such as up to ~9% for alanine and ~15% for isovaline, suggesting abiotic enantioselective processes occurred in the early solar system.^[135] For amplification of small initial ee to higher levels, autocatalytic reactions offer a pathway; the Soai reaction, involving asymmetric addition to pyrimidyl aldehydes, demonstrates how trace chirality (as low as 0.00005% ee) can escalate to near-100% ee through nonlinear autocatalysis, inspiring models for prebiotic networks where chiral products catalyze their own formation. In contrast, parity violation arising from the weak nuclear force introduces a minuscule energy difference between enantiomers (on the order of 10^{-14} to 10^{-17} kJ/mol), which is too small to drive significant ee in thermal equilibrium and thus unlikely to originate biological homochirality.^[136] Despite these proposals, no consensus exists on the primary mechanism for homochirality in abiogenesis, as most experiments achieve only modest ee of 10-50%, insufficient without further amplification for sustained prebiotic chemistry.^[132] Ongoing research emphasizes integrated scenarios combining initial biases from astrophysical or meteoritic sources with terrestrial amplification via minerals or autocatalysis to reach the required high ee.^[137]

Thermodynamic and Evolutionary Hurdles

One major thermodynamic challenge in abiogenesis is the necessity to sustain non-equilibrium chemical states capable of driving the emergence of ordered, self-sustaining systems from disordered prebiotic mixtures. Life requires continuous energy dissipation to maintain low-entropy configurations against the second law of thermodynamics, often through environmental gradients such as thermal or chemical disequilibria that prevent reversion to equilibrium. In prebiotic settings, this involves far-from-equilibrium processes where energy input, like ultraviolet radiation or geochemical fluxes, selectively enriches reactive molecules, but achieving persistent autocatalytic cycles remains difficult without modern enzymatic efficiency.^[138] A related hurdle is the low probability of establishing reliable self-replication, constrained by Eigen's error threshold, which limits the viable length of genetic polymers to approximately 10-100 nucleotides for typical prebiotic error rates of ~0.05-0.1 per base. Beyond this threshold, mutations overwhelm faithful copying, eroding informational fidelity and preventing the buildup of complex replicators essential for proto-life.^[139] This threshold underscores the rarity of transitioning from simple oligomers to robust, error-correcting systems in dilute prebiotic soups.^[140] The evolutionary transition from abiotic chemistry to Darwinian selection poses further barriers, as initial molecular populations must evolve heritable variation under selection pressures without collapsing into non-selective equilibria. Eigen's quasispecies model describes early replicator ensembles as dynamic mutant clouds, where superior variants dominate only if replication fidelity exceeds the error threshold, enabling the shift from random chemistry to competitive evolution in a pre-RNA context.^[141] However, bridging this gap requires not just replication but compartmentalization and metabolic coupling to sustain selective advantages. Open questions persist regarding the overall rarity of abiogenesis, potentially explaining the Fermi paradox through the "Great Filter" hypothesis, where the improbable emergence of self-replicating life acts as a cosmic bottleneck limiting intelligent civilizations. Additionally, assembling a minimal functional genome—estimated at around 200 essential genes for basic cellular operations—demands coordinated evolution of interdependent components, amplifying the improbability in unconstrained prebiotic environments. Recent thermodynamic models (as of 2025) highlight persistence as a precursor to replication and metabolism, selecting stable chemical systems under disequilibria.^[142] Studies also suggest abiogenesis may occur rapidly (~10^6 years) on habitable worlds, mitigating rarity concerns.^[143] Recent systems chemistry research addresses these hurdles by reconstructing integrated protocell models that combine membrane formation, RNA replication, and energy transduction in lipid vesicles, demonstrating emergent division and growth under thermal gradients. In parallel, AI-driven modeling explores vast prebiotic reaction spaces, using machine learning to predict plausible synthetic routes for biomolecules and identify low-probability pathways overlooked by manual simulation.^[144] Critiques highlight ongoing debates between deep-sea hydrothermal vent scenarios, which provide mineral surfaces and redox gradients but dilute organics, and surface aqueous environments like evaporating ponds, which concentrate monomers via wet-dry cycles yet expose them to destructive UV radiation.^[145] These divisions underscore the need for hybrid, integrated models that incorporate multiple mechanisms to overcome isolated thermodynamic and evolutionary barriers, including challenges like homochirality amplification.^[146]

References

[1]
The origin of life: what we know, what we can know and what we will ...
The DKS concept, simple in essence, does outline in the broadest terms the physico-chemical basis for abiogenesis. But that broad outline needs to be ...
[2]
The origin of life on Earth, explained | University of Chicago News
Earth is about 4.5 billion years old. Scientists think that by 4.3 billion years ago, Earth may have developed conditions suitable to support life. The oldest ...Missing: abiogenesis | Show results with:abiogenesis
[3]
A Production of Amino Acids Under Possible Primitive Earth ...
A Production of Amino Acids Under Possible Primitive Earth Conditions. Stanley L. MillerAuthors Info & Affiliations. Science. 15 ...
[4]
From Biochemistry to Biology – Astrobiology
Abiogenesis · The natural process by which life has arisen from non-living matter, such as simple organic compounds · The formation of life exclusively through ...The Building Blocks Of Life · The Miller-Urey Experiment · Abiogenesis<|control11|><|separator|>
[5]
Books on the emergence of life - NASA
Oct 1, 2019 · Be it on Earth or some other world, life had to begin via processes known as abiogenesis Obviously, there must have been an evolutionary ...Abiogenesis: How Life Began... · Protocells: Bridging... · Chemical Evolution And The...
[6]
(PDF) The Fundamental Underpinning of Biological Theory of ...
Mar 26, 2024 · This article explores the historical trajectory of spontaneous generation theory from its roots in Aristotelian philosophy to its refutation by pivotal ...
[7]
Pasteur's Papers on the Germ Theory
His discovery that living organisms are the cause of fermentation is the basis of the whole modern germ- theory of disease and of the antiseptic method of ...
[8]
Mechanism, vitalism and organicism in late nineteenth and twentieth ...
In the early twentieth century philosophical Mechanism became the foundation of a 'new biology' that sought to establish the life sciences on the same solid and ...
[9]
Pioneers of Origin of Life Studies—Darwin, Oparin, Haldane, Miller ...
Oct 21, 2024 · The two basic approaches to elucidating how life began both date from Darwin. The first, that of the experimentalists, stems from Darwin's famous “warm little ...
[10]
https://www.sciencedirect.com/science/article/abs/pii/S1369848605000191
[11]
Spontaneous generation | Examples & Experiments - Britannica
Sep 24, 2025 · Spontaneous generation, the hypothetical process by which living organisms develop from nonliving matter.
[12]
3.1: Spontaneous Generation - Biology LibreTexts
Apr 20, 2024 · The Greek philosopher Aristotle (384–322 BC) was one of the earliest recorded scholars to articulate the theory of spontaneous generation, the ...
[13]
Francesco Redi | Experimenter, Parasitologist, Poet - Britannica
In 1668, in one of the first examples of a biological experiment with proper controls, Redi set up a series of flasks containing different meats, half of the ...
[14]
True Science, Fake History
Jul 25, 2014 · The results were published in 1668 but to little effect. Although Redi was convinced insects could not pop out of dead animals, he was not so ...
[15]
Lazzaro Spallanzani (1729-1799) | Embryo Project Encyclopedia
Nov 1, 2007 · He published his results refuting spontaneous generation in 1765 and thereby initiated a lifelong correspondence with Bonnet. An avid and ...
[16]
Is Spontaneous Generation Real? - ThoughtCo
Oct 23, 2019 · In 1765, Italian biologist and priest Lazzaro Spallanzani, set out to demonstrate that microbes do not spontaneously generate. He contended that ...<|control11|><|separator|>
[17]
Spontaneous generation - Louis Pasteur - Britannica
Sep 24, 2025 · He showed that beef broth could be sterilized by boiling it in a “swan-neck” flask, which has a long bending neck that traps dust particles and ...Missing: 1861 | Show results with:1861
[18]
Louis Pasteur: Between Myth and Reality - PMC - PubMed Central
Apr 18, 2022 · In his fight against the concept of spontaneous generation, Pasteur was helped by Balard, who conceived the experiments with the swan neck ...
[19]
Germ Theory - World History Encyclopedia
Jul 24, 2023 · A German chemist, Justus von Liebig (1803-1873), one of the early founders of organic chemistry, suggested that as a result of a chemical ...
[20]
The Spontaneous Generation Controversy (1859-1880) - jstor
generation, heterogenesis and abiogenesis. In the early decades of the nineteenth century, spontaneous generation had gained its strongest support in Germany ...
[21]
Louis Pasteur, from crystals of life to vaccination - ScienceDirect
This view was strongly supported by most eminent chemists, such as Justus von Liebig, Jöns Berzelius and Friedrich Wöhler. ... Science, politics, and spontaneous ...Review · Crystals Of Life 1847 · The Germ Theory Of...<|control11|><|separator|>
[22]
Abiogenesis | Definition & Theory | Britannica
Sep 19, 2025 · Abiogenesis, the idea that life arose from nonlife more than 3.5 billion years ago on Earth. Abiogenesis proposes that the first life-forms generated were very ...
[23]
Estimating the ethical value of directed panspermia - ScienceDirect
Over time this hypothesis gained scientific credibility; in 1903, Svante Arrhenius proposed that bacterial spores might spread from living planets due to ...
[24]
A Short History of Panspermia from Antiquity Through the Mid-1970s
Panspermia is the philosophical proposition that the precursors of life are present in space and able to initiate life on reaching a suitable environment.
[25]
https://www.sciencedirect.com/science/article/pii/S009457652500181X
[26]
Directed panspermia - ScienceDirect.com
Directed panspermia is the theory that organisms were deliberately transmitted to Earth by intelligent beings on another planet.
[27]
Evidence for Extraterrestrial Amino-acids and Hydrocarbons in the ...
Dec 5, 1970 · Organic molecules found in meteorites seem to have been formed before the meteorites reached Earth.Missing: paper | Show results with:paper
[28]
Tardigrades survive exposure to space in low Earth orbit
Sep 9, 2008 · Tardigrades exposed to solar radiation had a very low survival and fitness, and in line with studies in bacteria [6] most specimens were killed ...
[29]
Tardigrades in Space Research - Past and Future - PMC - NIH
Oct 20, 2016 · The experiments showed that tardigrades can survive exposure to the space vacuum, but the addition of factors such as ultraviolet solar ...<|control11|><|separator|>
[30]
Are We from Outer Space? A Critical Review of the Panspermia ...
Criticisms aside, these experiments are a realistic method of testing the panspermia hypothesis – as Wainwright (2003) notes. Unless we disavow the methodology ...
[31]
Panspermia: Unlikely, unsupported, but just possible - ScienceDirect
The present situation is that panspermia is unlikely, so far completely unsupported, but is just possible for viable, and somewhat more so for dead, ...
[32]
[PDF] Lithopanspermia in Star-Forming Clusters
This paper considers the lithopanspermia hypothesis in star-forming groups and clusters, where the chances of biological material spreading from one solar ...
[33]
Cosmic History - NASA Science
Oct 22, 2024 · In the following minutes, an era called nucleosynthesis, protons and neutrons collided and produced the earliest elements – hydrogen, helium, ...
[34]
DOE Explains...Nucleosynthesis - Department of Energy
Nucleosynthesis first occurred within a few minutes of the Big Bang. At that time, a quark-gluon plasma, a soup of particles known as quarks and gluons, ...
[35]
Big Bang Nucleosynthesis
Light elements (namely deuterium, helium, and lithium) were produced in the first few minutes of the Big Bang, while elements heavier than helium are thought ...
[36]
What Were the First Stars Like? - NASA Science
Sep 3, 2025 · In other words, Population III stars were metal-free. (Astronomers refer to any element heavier than helium as a metal.) This might seem like a ...
[37]
Populating the periodic table: Nucleosynthesis of the elements
Feb 1, 2019 · These supernovae enrich the Universe in three ways. First, they eject the products of nucleosynthesis built up over the star's lifetime (Fig. 2) ...
[38]
Organic Molecules in Interstellar Space: Latest Advances - Frontiers
Mar 1, 2022 · Last 2 years, 30 prebiotic molecules have been detected in TMC-1, a dust-enshrouded gaseous cloud located at 400 light-years from the Sun in the ...Abstract · Introduction · Complex Organic Molecules in... · Molecules in the Distant...
[39]
First Light - Abraham Loeb
This implies that the first stars must have formed at a redshift z ~ 10 - 20, and reionized a substantial fraction of the intergalactic hydrogen around that ...
[40]
Scientists estimate solar nebula's lifetime | MIT News
Feb 9, 2017 · About 4.6 billion years ago, an enormous cloud of hydrogen gas and dust collapsed under its own weight, eventually flattening into a disk ...Missing: sources | Show results with:sources
[41]
Formation of Earth - National Geographic Education
Oct 19, 2023 · It happened roughly 4.6 billion years ago. The formation of the sun consumed more than 99 percent of the matter in the nebula. The remaining ...
[42]
How the Earth and moon formed, explained - UChicago News
The Earth formed over 4.6 billion years ago out of a mixture of dust and gas around the young sun. It grew larger thanks to countless collisions.Missing: sources | Show results with:sources
[43]
Theia slammed into Earth, left marks and then formed the Moon ...
Nov 8, 2023 · At the time of the impact, the solar system was around 50 million years old. It's 4.5 billion years old now. Simulations show evidence of Theia.<|separator|>
[44]
What is the Late Heavy Bombardment? - NASA Science
The Late Heavy Bombardment was a cataclysmic pummeling by asteroids around 4 billion years ago, caused by a shift in giant planet orbits.Missing: 4.1-3.8 | Show results with:4.1-3.8
[45]
Earth's Earliest Atmospheres - PMC - PubMed Central - NIH
Life probably arose on Earth after the moon-forming impact. It and subsequent impacts probably created transient reducing methane- or CO-rich atmospheres.Missing: H2O | Show results with:H2O
[46]
Evolution of the Atmosphere: Composition, Structure and Energy
The first atmosphere was formed by outgassing of gases trapped in the interior of the early Earth, which still goes on today in volcanoes.Missing: N2 H2O
[47]
The Origin of the Atmosphere | Volcano World
78% nitrogen, 21% oxygen, 1% argon, 0.03% carbon dioxide plus small amounts of water vapor. Early in Earth history, water vapor formed clouds, rain, and ...Missing: evolution | Show results with:evolution
[48]
Ancient Crystals Suggest Earlier Ocean - NASA Earth Observatory
Mar 1, 2006 · Since then, however, scientists have found zircons that date to almost 4.4 billion years ago. “That might not seem like a big difference—4.1 ...
[49]
4-Billion-Year-Old Crystals Offer Clues to the Origins of Life
Sep 24, 2018 · It is the most ancient fragment of Earth's crust yet found and contains zircons that date back nearly 4.4 billion years. Photography by NASA ...
[50]
Was plate tectonics occurring when life first formed on Earth?
Mar 30, 2023 · The research provides chemical evidence that plate tectonics was most likely occurring more than 4.2 billion years ago when life is thought to have first ...
[51]
Researchers find oldest undisputed evidence of Earth's magnetic field
Apr 24, 2024 · Without its magnetic field, life on Earth would not be possible since this shields us from harmful cosmic radiation and charged particles ...
[52]
Earth's magnetic field and its relationship to the origin of life ...
Earth's magnetic field, at least 4.2 billion years old, shielded from radiation, preserved water, and may have assisted early life and evolution.
[53]
Evidence for oceans pre-4300 Ma confirmed by preserved igneous ...
Oct 1, 2024 · The Hadean Jack Hills detrital (JHD) zircons from Western Australia include the oldest-dated samples of Earth at 4400 Ma (Wilde et al. 2001; ...
[54]
Jack Hills Zircon: Scientists Discover Oldest-Known Fragment of Earth
Feb 24, 2014 · A small fragment of zircon from a rock outcrop in Australia confirms that the Earth's crust first formed at least 4.4 billion years ago ...
[55]
The chemical composition of the early terrestrial atmosphere ...
May 23, 2007 · Our calculation results show that the Earth's early atmosphere is very reducing, rich in H2 and/or CH4, regardless of which meteoritic materials ...
[56]
When Did Life Likely Emerge on Earth in an RNA‐First Process?
Sep 24, 2019 · When Did Life Likely Emerge on Earth in an RNA-First Process? Prof ... Steven Benner is a Distinguished Fellow at the Foundation for ...
[57]
Continent formation through time | Geological Society, London ...
The earliest fragments of continental crust are of Archaean age (4.0–2.5 Ga). Only two fragments of early Archaean crust survive – the 4.0 Ga Acasta gneisses ( ...
[58]
3.7 billion year old biogenic remains - PMC
Nov 14, 2017 · 3.7 Billion year old inclusions inside garnet crystals contain 13C depleted carbonaceous material consistent with biogenic origin.Missing: biomarkers | Show results with:biomarkers
[59]
3.5 billion-year-old rock structures are one of the oldest signs of life ...
Nov 10, 2022 · Fossils called stromatolites from Western Australia were created by microbes 3.48 billion years ago.
[60]
Nano−porous pyrite and organic matter in 3.5-billion-year-old ...
Sep 25, 2019 · Stromatolites of the ∼3.5 billion-year-old Dresser Formation (Pilbara Craton, Western Australia) are considered to be some of Earth's ...Missing: oldest age
[61]
Uracil in the carbonaceous asteroid (162173) Ryugu - Nature
Mar 21, 2023 · Hayabusa2 spacecraft successfully delivered total 5.4 g of pristine samples, collected during two touchdown operations, from the C-type near- ...
[62]
Prebiotic chemicals—amino acid and phosphorus—in the coma of ...
May 27, 2016 · We report the presence of volatile glycine accompanied by methylamine and ethylamine in the coma of 67P/Churyumov-Gerasimenko measured by the ROSINA.
[63]
[PDF] THE 1953 STANLEY L. MILLER EXPERIMENT:
Fifty years ago, Science published in its 15 May 1953 issue the short, less than two-page, paper by Stanley L. Miller titled 'A production of amino acids ...
[64]
Primordial synthesis of amines and amino acids in a 1958 Miller H 2 ...
Mar 21, 2011 · This experiment marks the first synthesis of sulfur amino acids from spark discharge experiments designed to imitate primordial environments.
[65]
The Miller Volcanic Spark Discharge Experiment - Science
Oct 17, 2008 · The volcanic apparatus produced a wider variety of amino acids than the classic one. Release of reduced gases in volcanic eruptions accompanied ...
[66]
Prebiotic Significance of Extraterrestrial Ice Photochemistry
Nov 17, 2011 · Here, we report on experiments in which vacuum UV photo-irradiation of interstellar/circumstellar ice analogues containing H2O, CH3OH, and NH3 ...
[67]
Synthesis of prebiotic organics from CO 2 by catalysis with meteoritic ...
May 25, 2023 · We experimentally demonstrate that iron-rich meteoritic and volcanic particles activate and catalyse the fixation of CO 2 , yielding the key precursors of life ...
[68]
Discharge plasma for prebiotic chemistry: Pathways to life's building ...
Sep 23, 2024 · This discussion elaborates on the fundamental mechanisms of discharge plasmas and their likely role in fostering conditions necessary for the ...Missing: 2020s | Show results with:2020s
[69]
Prebiotic synthesis of α-amino acids and orotate from α-ketoacids ...
Jul 28, 2022 · The Strecker reaction of aldehydes is the pre-eminent pathway to explain the prebiotic origins of α-amino acids.Missing: Strecker | Show results with:Strecker
[70]
Selective prebiotic synthesis of phosphoroaminonitriles and ... - Nature
Feb 26, 2019 · Strecker amino acid synthesis appears to be prebiotic, but the high pKaH of ammonia (pKaH = 9.2) necessitates high pH reaction conditions to ...
[71]
Isotope effects at the origin of life: Fingerprints of the Strecker synthesis
Mar 15, 2022 · Strecker synthesis creates α-amino acids from prebiotically plausible substrates (cyanide, ammonia, and aldehydes) and is widely hypothesized to be a key ...
[72]
The Origin of RNA and the Formose–Ribose–RNA Pathway - PMC
Jun 19, 2024 · One of the oldest theories about ribose formation comes from the formose reaction [21]. The low yield of ribose [22,23] works against the mass ...
[73]
Prebiotic Synthesis of Ribose - Encyclopedia.pub
Jun 10, 2021 · The formose reaction creates a mixture of sugars with varying sizes and shapes, of which ribose makes up less than 1%. Albert Eschenmoser's ...
[74]
A Plausible Prebiotic One‐Pot Synthesis of Orotate and Pyruvate ...
Jan 10, 2022 · A prebiotic synthesis of the nucleobase orotate, and the citric acid cycle intermediate pyruvate, proceeds in a single pot from two small glycine derivatives.
[75]
Assessing the diversity of lipids formed via Fischer-Tropsch-type ...
Fischer-Tropsch-type (FTT) synthesis under hydrothermal conditions leads to a variety of biomarker-like lipids, e.g. linear and methyl-branched alkanes and ...
[76]
The Role of Lipid Membranes in Life's Origin - MDPI
Examples include essential fatty acids such as linoleic and arachidonic acid and the fat soluble vitamins: carotenoids such as vitamin A, the cholesterol ...Missing: abiogenesis | Show results with:abiogenesis<|control11|><|separator|>
[77]
Plausible Sources of Membrane-Forming Fatty Acids on the Early ...
The most commonly reported abiotic synthesis of fatty acids involves catalytic metal surfaces. Within this class of syntheses, Fischer–Tropsch ...
[78]
Boundary structures are formed by organic components of ... - Nature
Oct 1, 1985 · Deamer, D. Boundary structures are formed by organic components of the ... Dynamics of the vesicles composed of fatty acids and other ...
[79]
Coupled Growth and Division of Model Protocell Membranes
Mar 26, 2009 · Small unilamellar fatty acid vesicles grow when fed with fatty acid micelles and can be forced to divide by extrusion, but this artificial ...
[80]
The Emergence of Competition Between Model Protocells - Science
Sep 3, 2004 · We sought to detect the emergence of an adaptive cellular-level trait based on the physical properties of a model prebiotic vesicle system ...
[81]
The adsorption of nucleotides and polynucleotides on ...
No association of 5′-UMP to poly(U) bound to clay was detected. The possible role of montmorillonite clays in the prebiotic formation of RNA is discussed.
[82]
Montmorillonite catalysis of RNA oligomer formation in aqueous ...
Montmorillonite catalysis of RNA oligomer formation in aqueous solution. A model for the prebiotic formation of RNA.
[83]
Physical effects underlying the transition from primitive to modern ...
Mar 14, 2011 · MM Hanczyz, SM Fujikawa, JW Szostak, Experimental models of primitive cellular compartmentalization: Encapsulation, growth, and division.
[84]
Experimental Models of Primitive Cellular Compartments - Science
Experimental Models of Primitive Cellular Compartments: Encapsulation, Growth, and Division. Martin M. Hanczyc, Shelly M. Fujikawa, and Jack W. Szostak ...
[85]
[PDF] prigogine-lecture.pdf - Nobel Prize
The theorem of minimum entropy production expresses a kind of “inertial” property of nonequilibrium systems. When given boundary conditions prevent the system ...
[86]
[PDF] Entropy Production and the Origin of Life - Scirp.org.
Here we take such a thermodynamic perspective on the origin of life, recognizing that entropy production is not only the vital force of life, but the.
[87]
[PDF] Thermodynamic dissipation theory for the origin of life - ESD
Entropy pro- duction is a measure of the rate of the tendency of Nature to explore available microstates. The most important irre- versible process generating ...Missing: abiogenesis compartments
[88]
Illuminating Life's Origins: UV Photochemistry in Abiotic Synthesis of ...
Apr 21, 2021 · Reactivity and selectivity in photochemical prebiotic synthesis are discussed, as are their implications for origins of life scenarios and their plausibility.
[89]
A Prebiotic Precursor to Life's Phosphate Transfer System with an ...
Mar 6, 2024 · We demonstrate a prebiotic phosphate transfer system involving an ATP analog (imidazole phosphate) and histidyl peptides, which function as organocatalytic ...
[90]
A prebiotic basis for ATP as the universal energy currency
ATP is universally conserved as the principal energy currency in cells, driving metabolism through phosphorylation and condensation reactions.Missing: F0F1- ATPase
[91]
Origin of life: The RNA world - Nature
News & Views; Published: 20 February 1986. Origin of life: The RNA world. Walter Gilbert. Nature volume 319, page 618 (1986)Cite this article. 48k Accesses.
[92]
The Origins of the RNA World - PMC - PubMed Central
The general notion of an “RNA World” is that, in the early development of life on the Earth, genetic continuity was assured by the replication of RNA.
[93]
Synthesis of activated pyrimidine ribonucleotides in prebiotically ...
May 14, 2009 · Powner, M. W. et al. On the prebiotic synthesis of ribonucleotides: photoanomerisation of cytosine nucleosides and nucleotides revisited.
[94]
High-Yield Prebiotic Polymerization of 2′,3′-Cyclic Nucleotides ...
Jun 28, 2025 · Wet−dry cycles at mild alkaline pH drive high-yield spontaneous RNA polymerization from 2′,3′-cyclic nucleotides without added molecules, ...
[95]
Evolutionary transition from a single RNA replicator to a multiple ...
Mar 18, 2022 · The RNAs can undergo Darwinian evolution in a serial transfer experiment, and a previous attempt (120 rounds, 600 h) demonstrated the successive ...
[96]
Origin and Evolution of the Ribosome - PMC - PubMed Central
The modern ribosome was largely formed at the time of the last common ancestor, LUCA. Hence its earliest origins likely lie in the RNA world.
[97]
History of the ribosome and the origin of translation - PNAS
In the extant ribosome, specific segments of rRNA perform specific functions including peptidyl transfer, subunit association, decoding, and energy-driven ...Missing: abiogenesis | Show results with:abiogenesis
[98]
A Short Tale of the Origin of Proteins and Ribosome Evolution - PMC
Oct 26, 2022 · Ancestral insertions and expansions of rRNA do not support an origin of the ribosome in its peptidyl transferase center. J. Mol. Evol. 2015 ...Missing: seminal | Show results with:seminal
[99]
Origins and Early Evolution of the tRNA Molecule - PubMed Central
Dec 3, 2015 · Here, the origins and early evolution of tRNA are discussed in terms of various perspectives, including nucleotide ligation, chiral selectivity ...
[100]
On the origin of the translation system and the genetic code in the ...
May 31, 2007 · To understand how translation might have emerged, the nature and origin of the codon assignments in the universal genetic code are crucial.
[101]
Functional Capabilities of the Earliest Peptides and the Emergence ...
In doing so triphosphate becomes hydrolyzed to phosphate and pyrophosphate. The effect is synergy between peptide and polyphosphates. Polyphosphates are ...Missing: Ilan abiogenesis
[102]
In the Beginning was a Mutualism - On the Origin of Translation
Apr 30, 2018 · The proposed mechanism is in concordance with the hypothesis of a possible chemical co-evolution of RNA and proteins in the origin of the ...
[103]
The last universal common ancestor between ancient Earth ...
Aug 16, 2018 · All known life forms trace back to a last universal common ancestor (LUCA) that witnessed the onset of Darwinian evolution.Missing: timeline | Show results with:timeline
[104]
The nature of the last universal common ancestor and its impact on ...
Jul 12, 2024 · The last universal common ancestor (LUCA) is the node on the tree of life from which the fundamental prokaryotic domains (Archaea and Bacteria) diverge.
[105]
Funding: Interdisciplinary challenges - Nature Microbiology
Insufficient relevant content. The provided text from https://www.nature.com/articles/nmicrobiol2016118 is a preview of a news & views article titled "Funding: Interdisciplinary challenges" by Paul C. Blainey, focusing on funding issues for interdisciplinary research, not LUCA or related topics. No information is available on the definition, timeline, genomic evidence, thermophilic traits, metabolic inferences, phylogeny, or debates on LUCA complexity.
[106]
A consensus view of the proteome of the last universal common ...
Jun 3, 2022 · The universality of the genetic code suggests that the LUCA had a recognizable translation system that encoded the 20 proteinogenic amino acids ...<|separator|>
[107]
Geologic evolution of the Lost City Hydrothermal Field - AGU Journals
Dec 14, 2015 · The field hosts spectacular carbonate towers rising 60 m above the seafloor that vent basic fluids enriched in hydrogen, methane, and other low ...
[108]
Lost City Pumps Life-essential Chemicals at Rates Unseen at ...
Jan 31, 2008 · The Lost City hydrothermal vent field lies about 2,300 miles east of Florida, along the Mid-Atlantic Ridge, at a depth of 2,600 feet.
[109]
H2-rich fluids from serpentinization: Geochemical and biotic ... - PNAS
Aug 23, 2004 · Geochemists report hydrogen-bearing gases trapped in spring waters issuing from serpentinizing peridotites and ancient serpentinites undergoing modern ...<|separator|>
[110]
Organic synthesis associated with serpentinization and carbonation ...
Jan 13, 2022 · Serpentinization is an abiotic organic synthesis mechanism whereby basaltic rocks react with an aqueous fluid, producing serpentine minerals, ...
[111]
The Origin of Life in Alkaline Hydrothermal Vents | Astrobiology
These thin barriers separate alkaline (pH 11) hydrothermal fluids from mildly acidic (pH 5–7) ocean waters. The leaky walls do not prevent mixing, but ...
[112]
On the origins of cells: a hypothesis for the evolutionary transitions ...
We propose that life evolved in structured iron monosulphide precipitates in a seepage site hydrothermal mound at a redox, pH and temperature gradient.
[113]
Peptide Synthesis in Early Earth Hydrothermal Systems | Astrobiology
Apr 16, 2009 · In contrast to previous hydrothermal studies, we demonstrate that peptide synthesis is favored in hydrothermal fluids and that rates of peptide ...Missing: formation simulations<|separator|>
[114]
Hybrid organic–inorganic structures trigger the formation of primitive ...
Aug 10, 2023 · Hydrothermal vents have long been suggested as an ideal location where abiogenesis could have occurred. Simultaneously, a large volume of ...
[115]
A Field Trip to the Archaean in Search of Darwin's Warm Little Pond
A Field Trip to the Archaean in Search of Darwin's Warm Little Pond. by. Bruce Damer ... 2016 / Accepted: 20 May 2016 / Published: 25 May 2016. (This article ...
[116]
The Hot Spring Hypothesis for an Origin of Life - PMC
Wet-dry cycles in fresh water would be abundant in the prebiotic environment as long as volcanic land masses had emerged from the global ocean, and a ...Missing: soup | Show results with:soup
[117]
Silica Precipitation in a Wet–Dry Cycling Hot Spring Simulation ...
Jan 14, 2020 · Silica precipitation is a common phenomenon in terrestrial hot springs and is closely associated with life in modern systems.
[118]
Searching for lost nucleotides of the pre-RNA World with a self ...
Dec 12, 2018 · Our search for the origin of nucleotides has shown that the drying pond model naturally enables the prebiotic formation of nucleotides if we ...
[119]
Prebiotic chemistry in eutectic solutions at the water–ice matrix
Jun 1, 2012 · A crystalline ice matrix at subzero temperatures can maintain a liquid phase where organic solutes and salts concentrate to form eutectic solutions.Missing: formose | Show results with:formose
[120]
https://royalsocietypublishing.org/doi/10.1098/rstb.2002.1183
[121]
Origin of first cells at terrestrial, anoxic geothermal fields - PNAS
The hypothesis described here implies that cells invaded the oceans at a relatively late, advanced stage of evolution, after elaborate, modern-type membranes ...Missing: abiogenesis | Show results with:abiogenesis
[122]
Cassini finds molecular hydrogen in the Enceladus plume - Science
Apr 14, 2017 · The use of OSNB mode during the INMS observations of E21 on 28 October 2015 enabled the detection and quantification of H2 in the plume.Missing: abiogenesis | Show results with:abiogenesis
[123]
Subsurface exolife | International Journal of Astrobiology
Apr 4, 2018 · We study the prospects for life on planets with subsurface oceans, and find that a wide range of planets can exist in diverse habitats with ...
[124]
The Origin of Biological Homochirality - PMC - PubMed Central
The proteinogenic amino acid serine shows a eutectic of 99% ee, meaning that a nearly homochiral solution is achievable even when the overall ee of the ...Missing: abiogenesis | Show results with:abiogenesis
[125]
Chapter 4: A Geological and Chemical Context for the Origins of Life ...
Mar 18, 2024 · The focus of this chapter is the period during which life likely originated: from the Hadean Eon (4.56–4.0 billion years ago [Ga]) up to the ...
[126]
Biological homochirality as result from a single event - ScienceDirect
The parity-violating effect of the weak force is much too small to be statistically significant for the origin of biological homochirality.
[127]
The Search for Chiral Asymmetry as a Potential Biosignature in our ...
Therefore, the detection of l- or d-enantiomeric excesses (ee) of chiral amino acids and sugars could be a powerful indicator for extant or extinct life on ...
[128]
Nonequilibrium abundances for the building blocks of life
May 2, 2019 · It is well known that nonequilibrium conditions of some kind are necessary for life. The degree by which the abundances are improved depends, of ...
[129]
Historical Perspective on the Discovery of the Quasispecies Concept
Sep 29, 2021 · The quasispecies concept owes its theoretical origins to a model for the origin of life as a collection of mutant RNA replicators. Independently ...
[130]
Computational studies of prebiotic chemistry at the age of machine ...
Sep 23, 2025 · Machine learning (ML) is rapidly transforming research in prebiotic chemistry. In particular, ML-based interatomic potentials enable the ...Missing: pathways abiogenesis
[131]
Intrinsic concentration cycles and high ion fluxes in self-assembled ...
Oct 18, 2019 · We demonstrate here that hydrothermal vents can function just as well as, or better than warm little ponds in terms of providing an environment ...Missing: debate | Show results with:debate
[132]
The Future of Origin of Life Research: Bridging Decades-Old Divisions
Here we focus on pressing questions and recent developments that bridge the classical disciplines and approaches, and highlight expectations for future ...