In what ways is the atmosphere of the earth different from the gaseous consistency of the early universe

I'll connect it with the formation of simple organic molecules since it describes that the atmosphere was composed of different gases mainly methane, ammonia and hydrogen and was deprived of oxygen and carbon and other biological gases or nearly.   
In the most popular Miller-Urey experiment, the most living organisms were first developed under the formation of the simple macromolecules that composes most organelles in the cells of a living organism. It started with the gases –methane, ammonia and hydrogen which came in contact with electric spark that aided the first formation of the basic components like amino acids, nucleic acids and RNA. Then resulted to the development of prokaryotes or the autotrophs.