According to Oparin and Haldane, the primitive earth conditions were of high temperature with volcanic storms having a reducing atmosphere, containing ${\mathrm{C}\mathrm{H}}_4,\mathrm{ }{\mathrm{N}\mathrm{H}}_{\mathrm{3,}}$ H2 etc., in the vapour state. They proposed that the first form of life could have come from the pre-existing non-living organic molecules by the chemical evolution process.