OPARIN'S THEORY OF THE ORIGIN OF LIFE: ORIGIN, POSTULATES - BIOLOGY - 2024

The theory of Oparin the origin of life, also known as the "Theory of primitive or primordial soup" tries to explain how life originated on Earth in conditions typical of millions of years ago when they emerged the first organic molecules.

This theory established by Oparin is one of the most accepted in the scientific community. It remains valid, even with the many advances in modern science, as new related discoveries manage to complement and strengthen it.

Photograph by Aleksandr Oparin (Source: Pavel Troshkin via Wikimedia Commons)

Oparin, in his writings, classified living organisms (biotic) at a level of organization of non-living matter (abiotic). He proposed, then, that this non-living matter was progressively changing and becoming more complex, until it formed the first living cells.

Oparin's theory opened the doors for the development of a branch of biological sciences known as "Synthetic Biology." This science tries to recreate the environmental conditions in which a "primitive soup" gave rise to the living organisms that today inhabit the earth.

A similar theory was put forward independently by the evolutionary biologist John Haldane, who named the first late Precambrian bodies of water, which were mainly composed of metallic elements and water, as "Primitive Soup".

Origin of the theory

Oparin's theory was proposed by Aleksandr Ivanovich Oparin, who was born in 1894 in a small Russian town called Uglich. From a very young age, Oparin was already passionate about plants and was familiar with Darwin's evolutionary theories.

He studied Plant Physiology at the University of Moscow, where, years later, he taught at the chairs of Biochemistry and Plant Physiology.

It was during his university studies that Oparin began to have serious concerns about microorganisms that, made up of only carbon, nitrogen and water atoms, have the ability to organize themselves to perform complex processes such as photosynthesis.

In 1923, Oparin published his experiments in a book he entitled "The Origin of Life." This book contains the theory that, together with the contributions of another researcher of the time named John Haldane, seeks to explain how the primordia of life emerged on our planet.

Oparin's text explains, with a very simple and didactic language, how the "evolution" of organic matter began before the formation of planet earth. It also explains how organic matter is formed by the action of solar rays, volcanic eruptions and electrical discharges of natural origin.

It is important to highlight that Oparin fervently opposed the theory of spontaneous generation, supporting his ideas on Darwin's theory of evolution and Mendeleev's "abiogenic" synthesis of oil; establishing that the beginning of life was due to a kind of "chemical evolution" that organized the elements of the primitive earth to form complex molecules.

Postulates

Although almost 100 years have passed since Oparin put forward his theory, it is still valid today. Oparin's conciliatory approach, which brings together disciplines as diverse as chemistry, astronomy, physics, and biology, offers, for many scientists, a rational approach to explaining how life formed on earth.

Oparin locates the emergence of life during the Precambrian period, where a highly reducing atmosphere existed, rich in two of the most abundant elements of living organisms: carbon (in the form of methane and cyanogens) and nitrogen (in the form of ammonia).

His theory was based, mainly, on the fact that the energy from ultraviolet light, volcanoes and electrical storms caused the precipitation of water that was in gaseous form, causing torrential rains that precipitated other compounds such as ammonia., methane, nitrogen, etc.

Torrential rains drove the precipitated elements into the seas, creating what Oparin called a "primitive broth." This broth served as the stage for a series of chemical reactions that gave rise to the first organic molecules similar to amino acids.

These colloidal "amino acid-like" molecules and others of a similar nature spontaneously organized to form peptide, protein and lipid-like structures, which Oparin named coacervates.

Later, the coacervates became even more specialized, managing to form structures very similar to the living cells that we know today.

These primitive "cells", over time, acquired the ability to develop a primitive metabolism, taking chemical compounds from the environment to extract food and energy from them, in order to survive and multiply.

Natural selection in coacervates

The coacervates proposed by Oparin, as already mentioned, used small molecules captured from the surrounding environment for food and energy. According to Oparin, these molecules were assimilated by other larger molecules, whom he called "primitive enzymes" of the coacervates.

The acquisition of an absorption and assimilation mechanism within each coacervate would represent an advantage over the other coacervates, therefore, the coacervates with a better assimilation capacity would grow faster and more efficiently.

Oparin determined that there was a growth limit for the "most successful" coacervates at a point where, thermodynamically, they became unstable. Consequently, the coacervates began to compartmentalize or "subdivide" into smaller coacervates.

The ability to divide large coacervates into smaller coacervates would increase the amount of coacervates of this type in the middle. These coacervates, being found in greater numbers or frequency, could have exerted a kind of “selective pressure” on the others, favoring those with a greater capacity to “divide” or segment.

Another characteristic of the coacervates that could have exerted a kind of “natural selection” on the others was, perhaps, the capacity to synthesize some energy metabolite from the food obtained from the primitive broth where they “grew”.

Thus, only coacervates capable of metabolizing environmental compounds and producing their own food and reserve energy probably survived.

Topicality of the theory

Darwin's theory of natural selection was crucial for Oparin to make sense of "competition" and "prevalence" among coacervates. Even years later, with the discovery of genes and hereditary material, Oparin attributed to these molecules the responsibility for a large part of the replication of coacervates.

Currently, many biologists are dedicated to the recreation of the primitive conditions of the earth that gave rise to the coacervates proposed by Oparin.

One of the most famous experiments of this type was that of Stanley Miller and Harold Urey, who experimentally verified the "abiogenesis" of amino acids such as glycine (glycine type).

Various scientists specialized in synthetic biology carry out experiments to achieve, artificially, the organization of life, but based on compounds other than carbon, suggesting that this "life" may be the type of life that we find on other planets.

Themes of interest

Theories of the origin of life.

Chemosynthetic theory.

Creationism.

Panspermia.

Theory of spontaneous generation.

References

1. Das, A. (2019). The Origin of Life on Earth-Viruses and Microbes. Acta Scientific Microbiology, 2, 22-28.
2. Fry, I. (2006). The origins of research into the origins of life. Endeavor, 30 (1), 24-28.
3. Herrera, AS (2018). The Origin of Life According to Melanin. MOJ Cell Sci Rep, 5 (1), 00105.
4. Kolb, VM (2016). Origins of Life: Chemical and Philosophical Approaches. Evolutionary Biology, 43 (4), 506-515.
5. Lazcano, A. (2016). Alexandr I. Oparin and the origin of life: a historical reassessment of the heterotrophic theory. Journal of molecular evolution, 83 (5-6), 214-222.
6. Oparin, AI (1957). The origin of life on the earth. The origin of life on the earth., (3rd Ed).