Endogenous Precursors of Life
From Earth's Depths to the First Cell
In the depths of the ancient Earth and in cosmic clouds, a secret was hidden that waited billions of years for its moment to become life.
What Are Endogenous Precursors of Life?
Beneath the thickness of the primary ocean and in the heated depths of the young Earth, long before the appearance of the first cell, amazing processes occurred. Endogenous carbon and hydrocarbon precursors are chemical compounds that formed in the depths of the planet and became the building blocks for the first life. Unlike organic matter that could have been brought by meteorites or synthesized in the atmosphere under the action of lightning, these substances arose in geological processes occurring in the Earth's crust and mantle.
Endogenous precursors of life are carbon and hydrocarbon compounds that formed in the geological conditions of early Earth: in magma chambers, at the boundary of rocks and hydrothermal systems, in zones of volcanic activity. These compounds became the basis for more complex organic molecules necessary for the emergence of life.
Alexey Alexandrovich Marakushev, a Russian academician specializing in geochemistry and petrology, developed a concept according to which living matter originated from the depths of the Earth. According to his research, fluid systems (hot solutions of gases and minerals) in the Earth's interior contained carbon and hydrocarbon compounds that served as the basis for prebiotic chemistry and the subsequent emergence of life2 .
Key Precursor Compounds
Polycyclic Aromatic Hydrocarbons (PAHs)
Flat multi-ring structures of carbon and hydrogen atoms capable of self-organization5 .
Methane Series Hydrocarbons
Simplest organic compounds that could serve as the basis for the synthesis of more complex molecules2 .
Fullerenes
Spherical carbon molecules discovered in space and potentially present on early Earth7 .
PAH World Theory: Bridge Between Chemistry and Biology
One of the most interesting hypotheses explaining the transition from non-living to living matter is the polycyclic aromatic hydrocarbon world hypothesis. According to this theory, PAHs became the missing link that allowed the first biopolymers to form5 .
How PAHs Helped Create RNA?
The mechanism proposed within this hypothesis is impressive in its simplicity and logic:
Self-organization
Flat PAH molecules in an aqueous environment spontaneously assembled into stacks with a distance between rings of 0.34 nm, which exactly matches the distance between nucleotides in RNA and DNA chains5 .
Attachment of Nitrogenous Bases
Purine and pyrimidine bases—key components of nucleic acids—attached to PAH rings via hydrogen bonds5 .
Backbone Formation
Linking molecules, such as formaldehyde oligomers, inserted between nitrogenous bases, forming a proto-RNA chain5 .
Detachment
Changes in environmental acidity led to the detachment of the newly formed RNA-like molecule from the PAH template5 .
Comparison of Prebiotic Evolution Hypotheses
| Hypothesis | Primary Environment | Key Compounds | Advantages | Problems |
|---|---|---|---|---|
| PAH World5 | Aqueous environment with PAHs | Polycyclic aromatic hydrocarbons, nucleotides | Explains 0.34 nm step in RNA, PAHs widespread in Universe | Insufficient experimental confirmation |
| RNA World1 | Primordial soup | RNA, ribozymes | RNA combines catalysis and information storage | Difficulty of abiogenic synthesis of long RNAs |
| Coacervate Theory6 9 | Primordial soup | Proteins, lipids | Experimentally shown formation of coacervates | No mechanism of heredity |
| Endogenous Theory2 | Earth's interior, hydrothermal systems | Carbon and hydrocarbon compounds | Uses energy of Earth's interior | Difficulty modeling conditions |
Discovery in the Perseus Cloud: Cosmic Confirmation
In 2023, an international research team made a discovery that became a strong argument in favor of hypotheses about the wide distribution of prebiotic molecules in the Universe. In the Perseus molecular cloud, an area of active star formation, numerous organic compounds were discovered7 .
Cosmic Significance
This discovery confirms that the main building blocks of life are widely distributed in cosmic space and could be delivered to young planets by meteorites and comets, or form directly in planetary systems7 .
Main Prebiotic Molecules Discovered in the Perseus Cloud7
| Molecule | Formula | Role in Prebiotic Chemistry |
|---|---|---|
| Polycyclic aromatic hydrocarbons | PAHs | Templates for assembly of first biopolymers |
| Fullerenes | C₆₀, C₇₀ | Carbon frameworks, potential catalysts |
| Cyanoacetylene | HC₃N | Precursor of nitrogenous bases |
| Acetylene | C₂H₂ | Starting compound for synthesis of complex hydrocarbons |
| Benzene | C₆H₆ | Basic structural element of aromatic systems |
| Ammonia | NH₃ | Nitrogen source for amino acids and nucleotides |
Experimental Confirmation: From Theory to Practice
Although the PAH world hypothesis needs further experimental verification, other aspects of prebiotic chemistry have already been confirmed in laboratory conditions.
In 1953, Stanley Miller and Harold Urey conducted a landmark experiment that demonstrated the possibility of abiogenic synthesis of organic substances under conditions simulating early Earth9 .
Experimental Methodology:
Results and Significance:
As a result of the experiment, amino acids (glycine, alanine, aspartic acid), organic acids, monosaccharides and precursors of nucleotides were synthesized9 . This was a powerful confirmation that the main building blocks of life could have formed on early Earth through abiogenic pathways from simple inorganic compounds.
Main Results of the Miller-Urey Experiment9
| Compound Category | Specific Examples | Significance for Life's Origin |
|---|---|---|
| Amino acids | Glycine, alanine, aspartic acid | Building blocks of proteins |
| Organic acids | Formic, acetic, lactic acid | Participants in metabolic processes |
| Monosaccharides | Simple sugars | Energy sources, nucleotide components |
| Nucleotide precursors | Purine and pyrimidine bases | Components of RNA and DNA |
Scientific Toolkit: Reagents and Research Methods
Modern research in the field of prebiotic chemistry uses various methods and reagents to model early Earth conditions and test hypotheses.
Key Research Reagents and Their Functions
Polycyclic Aromatic Hydrocarbons (PAHs)
Used to study self-organization and formation of proto-RNA structures5 .
Amino Acids (D- and L-isomers)
Used in experiments on abiogenic synthesis to study the emergence of chirality8 .
Nucleosides and Nucleotides
Main reagents in RNA world research and replication processes8 .
Lipids and Fatty Acids
Studied in the context of membrane formation and protocells6 .
Fullerenes
Studied as possible participants in prebiotic processes and catalysts7 .
Research on endogenous carbon and hydrocarbon precursors of living matter paints a complex picture of life's emergence. Likely, the origin process was combined: some compounds formed in Earth's depths, others were delivered from space, and still others were synthesized in the atmosphere under the influence of lightning energy and ultraviolet radiation1 7 .
Discoveries in recent years, such as the detection of complex organic molecules in star-forming regions, show that chemical evolution is a fundamental property of the Universe. Prebiotic compounds are widely distributed in space, and the processes that led to the emergence of life on Earth may also occur on other planets7 .
The study of endogenous precursors of life continues, and each new discovery in geology, astronomy, and biochemistry brings us a little closer to unraveling one of the most fundamental mysteries of the universe - how life arose from non-living matter.