Question

Describe in brief the Oparin-Haldane theory of origin of life. How does meteorite favour this hypothesis?

Answer 1

The Oparin-Haldane theory, also known as the Abiogenic theory of the origin of life, was proposed by Aleksander I. Oparin in 1924 and J.B.S. Haldane in 1929. This theory suggests that life originated through a gradual chemical evolution process on the primitive Earth and was not a sudden event. The main points of the theory are:

1. Origin of Earth and primitive atmosphere: Early Earth was a hot, fiery ball of gases and vapors. As it cooled, atoms stratified by density, and light gases (hydrogen, oxygen, nitrogen, carbon, argon) formed a primitive reducing atmosphere with no free oxygen.
2. Origin of inorganic molecules: High temperatures caused elements to combine into oxides, carbides, nitrides, and superheated steam.
3. Origin of organic compounds: In the reducing atmosphere, simple organic molecules like hydrocarbons, aldehydes, ketones, acids, sugars, amino acids, and nitrogenous bases formed by condensation and polymerization.
4. Aggregation into colloids and coacervates: Organic molecules aggregated into coacervates, colloidal droplets with a membrane-like boundary, seen as precursors to primitive cells.
5. Development of autocatalytic systems and nucleoproteins: Self-replicating nucleic acid chains formed, leading to protovirus-like structures that could duplicate in the ocean.
6. Origin of primitive cellular life: Coacervates with nucleoproteins evolved into primitive cellular forms resembling bacteria.
7. Evolution of autotrophism: Initially heterotrophic anaerobes consumed organic nutrients; later, autotrophic organisms evolved that synthesized their own food via chemoautotrophy and photosynthesis (using bacteriochlorophyll and then true chlorophyll).

Meteorites favor the Oparin-Haldane hypothesis as they contain organic compounds such as amino acids, purines, pyrimidines, and carbonyl compounds. The presence of these abiotic organic molecules in meteorites supports the idea that the building blocks of life could have formed naturally and delivered to early Earth, supplementing the prebiotic chemistry occurring in the primitive atmosphere and oceans. This extraterrestrial input of organic molecules strengthens the concept that life's origin involved chemical evolution from simple molecules under reducing conditions, as proposed by Oparin and Haldane.