Miller- Urey experiment suggested the primitive earth's atmosphere and proved the chemical origin of life. A primitive earth's atmosphere was simulated in an experimental set up with methane, ammonia, hydrogen and water. Electric sparks were created similar to lightning and the water vapour generated was allowed to cool and condense. This sample, when analysed after purification was found to contain amino acids. Thus, proving the chemical origin of life.
Though the experiment proved the synthesis of amino acids which are the building blocks of proteins, it failed to explain the assembly of proteins from the amino acids. The information for the coding these proteins in presence of the DNA or the RNA was also not explained. Also, the gases used in the experiment were not abundant in the primitive earth's atmosphere. Thus, scientists now believe that Miller-Urey experiment was not an accuarate depicction of the conditions on the early earth.