The origin of life has been the greatest myth of the universe. Life being the mystery behind every living creature regardless its identity or personality, has been a very hard nut to crack when it comes to defining it, and locating its origin. Life might sound simple but it goes a long way differentiating the living from the non-living. But how does the living acquire this distinct quality? This is a question that has cost many philosophers and scientist their lifetime trying to puzzle out. So let’s see how science has been able to explain the phenomenon behind Life.
Early Belief
The story of how the world comes to form or how life first existed on it is as diverse as the number of cultures of the world. Almost every culture has a way of defining their origin. But something common among these stories is a belief that all creations are made by a magnificent supreme being. They believe the earth and all that is in it were created by a celestial mighty being, “god”.
This was even strengthened by the western theological belief according to the biblical record of creation. The first book of the bible (Genesis) recorded that the earth and everything on or in it was created by Almighty God over a period of six days. For many years , The majority of the communities of the world held on to this mythological belief until the middle of the nineteenth century, when it becomes clear that living organisms are subjected to the same physical and chemical laws just as non-living things. Does that mean they have the same origin as the non living things?
Basics of Life
As popularly defined, Life or living system is any system that posses the ability to metabolize; eat, breath, sense, grow, excrete, reproduce and die.
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Preceding Theories
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Dating back to the ancient Greek, a trend of successive philosophers has questioned the belief behind the emergence of the physical world. They diverge from the preliminary mythological knowledge and focused on practical knowledge in making philosophical assumption. These philosophers viewed the concept of origin of life from two perspectives; the monistic and the pluralistic view. The monists assumed that the origin of the world is from a single substance while pluralists held to the belief that creation would have been from a mixture that exhibit random motion and having its particles collide, bind and separate thereby forming life by "Chance". The Greek philosopher “Thales of Miletus” was the first to give a pure natural explanation of the origin of the world independent of mythological abstract. He assumed that life had emerged from water.
Early Hypothesis : Oparin-Haldane Soup Theory
The basic and fundamental theory of the origin of life was proposed by two scientists; Russian chemist Alexander I. Oparin and British scientist John B. Haldane in the 1920s.
According to this hypothesis, John D. Bernal, an Irish scientist, summarizes the process of biosynthesis (origin of life) in 1949 in three stages;
- Origin of biological monomers
- Origin of biological polymers
- Evolution from molecules of cells
The hypothesis of “Soup Theory” stated by Oparin and Haldane was supported by an experiment by Stanley L. Miller and Harold C. Urey in 1952 to demonstrate how organic molecules are formed from primordial inorganic ingredients.
Millar-Urey experiment
Being that the Oparin-Haldane’s hypothesis was widely accepted , it served as a framework from other succeeding research.
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Further Experiments and Modifications
The Urey-Miller experiment is regarded as the classic experiment in investigating the origin of life. Although the experiment vividly support the Oparin hypothesis but did not end the journey, on the contrary, it serves as a poke for new ideas and experiments. Recent investigation and experiments have created rooms for ideas, hypothesis and discoveries that get the story more complicated.
- Examination of the extract from miller’s experiment with advanced analytical procedures showed more amino-acids than was initially discovered by miller.
- Wolman N. MacNevin (at the Ohio University) discovered biochemicals relating to earth’s early primordial molecules while performing an experiment similar to that of miller (although he did this independent or ignorant of any theory of evolution). He was passing 100000 volt spark through methane and water vapour.
- Experiment performed by Jeffrey Bada- adding iron and carbonate minerals to the initial ingredients of the miller’s experiment. The products were very rich in amino acids. This suggest that the early atmosphere might contain carbondioxide and Nitrogen.
- In 1961, Joan Oro discovered that RNA and DNA nucleobases as well as amino acids could be obtained through simulated prebiotic chemistry with a reducing atmosphere. This suggest RNA world hypothesis which proposed that RNA being able to serve as a gene carrier and enzyme could have been the basis of pre-cellular life.
Based on these subsequent experiments it is very clear that there is no difficulty in synthesizing or forming the molecules that are necessary for life from their inorganic precursors. However J.D. Bernal concluded that “It is not enough to explain the formation of such molecules, what is necessary is a physical chemical explanation of the origin of these molecules that suggest the presence of suitable sources that sinks for free energy.
Conclusion
Many scientist have spent their lifetime trying to unravel the principle behind the phenomenon that bridge between the non-living molecules and the living organism. Yet no one has been able to obtain the characteristic called Life by combining these elementary molecules.
References:
- Abiogenesis: https://en.wikipedia.org/wiki/Abiogenesis
- Definition of Life: https://www.britannica.com/science/life
- Ingredients of Life: https://www.livescience.com/32983-what-are-ingredients-life.html
- Basic Molecules of Life: https://basicbiology.net/biology-101/molecules-of-life/
- Oparin-Haldane Hypothesis: https://en.wikibooks.org/wiki/Structural_Biochemistry/The_Oparin-Haldane_Hypothesis
- Miller-Urey Experiment: https://en.wikipedia.org/wiki/Miller%E2%80%93Urey_experiment
- Oparin-Haldane Hypothesis: https://en.wikibooks.org/wiki/Structural_Biochemistry/The_Oparin-Haldane_Hypothesis
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