The first form of life could have come from pre-existing non living organic molecules (RNA , protein etc.) , and that formation of life was preceded by chemical evolution / formation of diverse organic molecule from inorganic constituents , the condition on earth were high temperature (Volcanic storms) reducing atmosphere (containing CH4, NH3, etc) , Miller in his experiment created electric discharge in a closed task , containing CH4 , H2 , NH3 and water vapour at 800° C , and observed the formation of aminoacids / organic compounds , which supported chemical evolution.
