Origin of Life (Part-II)

6. MODERN THEORY: The modern theory is also known as “chemical theory” or theory of primary abiogenesis. In the modern theory, the hypothesis of abiogenesis was proposed with a condition that the non-living materials can give rise to life in the condition of primitive earth. The condition of the primitive earth is different from the present conditions which donot permit abiogenesis. The idea of chemical theory was put forward by two scientist, A.I. Oparin and J.B.S Haldane. It has made following assumptions:

1. Spontaneous generation of life under the present environment is not possible.  
2. Earth’s atmosphere ~1 billion years is very different from the current conditions.
3. Primitive earth’s atmosphere was reducing in nature.
4. Under these conditions, the chemical molecules (inorganic molecules) react with each other through a series of reactions to form organic substances and other complex biomolecules.
5. The solar energy and UV radiation provided the energy for the chemical reactions.

Experimental Evidences supporting chemical theory: The hypothesis proposed by Haldane didn’t find much support without scientific experimentation. To conclusively support the chemical theory, miller and urey conducted experiment in mimicking primitive earth environment. The experimental design used for the experiment is given in the Figure 4.1. The experimental setup consists of a glass flask, a condenser, and a liquid flask interconnected with tubes and a source of electric spark to provide energy (Figure 4.1). He introduced a mixture of methane (CH4), ammonia (NH3), and hydrogen (H2) in the ratio of 2:2:1 and water (H2O) vapor at 8000C. he allowed to circulate the mixture into this closed glass apparatus for 18 days continuously. He provided energy in the form of spark by supplying electricity of 75000 volts through two electrodes. The electric sparks mimicks lighting in the primitive earth atmosphere. While passing the mixture, gases were passes through a liquid flask to simulate the volcano. The mixture was collected from the stop cock and analyzed using chromatographic and calorimetric techniques. The analysis of mixture indicates the presence of amino acids such as glycine, alanine, aspartic acid, nitrogen base adenine and