Stanley Miller and Harold Urey in 1953 performed an experiment to clearly demonstrate that ultraviolet radiations or electrical discharges or a combination of these can produce complex organic compounds from a mixture of Electric discharge was created in a closed flask containing CH4,NH3,H2 in the ratio 2 : 1 : 2 as shown in fig. 7.1.
The conditions were set similar to those of the primitive atmosphere in the laboratory.
He observed formation of amino acids while in similar experiments performed by other scientists the presence of complex molecules like- sugar, pigments, nitrogen bases and fats in the flask were also observed.
Thus, Miller-Urey experiment supported the theory of abiogenesis followed by chemical evolution. Analysis of meteorite content also revealed similar compounds indicating that similar processes are occurring else where in space. Thus with these limited evidences, the idea of chemical evolution was more or less accepted.