Oparin - Haldane theory of chemical evolution states that life originated from pre-existing, non-living organic molecules.
In 1953, S.L. Miller observed formation of amino acids from hydrogen and water vapour at 800 degree centigrade. It is stated that life originated from pre-existing non-living organic molecules. When the meteorites were analysed, it was observed that presence of similar compounds was confirmed which conclude that similar process is going on elsewhere in the space.