Oparin and Haldane proposed that the first from of life could have come from preexisting non living organic molecules and that formation i.e. formation of diverse organic molecule from inorganic constituents. The conditions on earth were-high temperature, volcanic storms, reducing atmosphere containing `CH_(4),NH_(3)` ect. In 1953 S.L. Miller, an American scientist created similar conditions in a laboratory scale. He created electric discharge in a closed flask containing `CH_(4),H_(2),NH_(3)` and water vapour at `800^(@)C`. He observed formation of amino acid, while others observed formation of sugars, nitrogen bases, pigment and fats. With this limited evidence, the first part of the conjectured story i.e. chemical evolution was more or less accepted.
The first non-cellular forms of life could have originated 3 billion years back.
