How did the first fermenting autotrophs appeared? What about the first aerobic beings?
A heterotrophic hypothesis asserts that the first living beings were the fermenting heterotrophs. The Fermentation released carbon dioxide (CO2) and then the atmosphere became enriched by this gas. By the mutation and the natural selection organisms capable of using carbon dioxide and light to synthesize organic material appeared and these would have been the first photosynthetic beings (that were also fermenting beings since there was no abundance of oxygen).
Ever since photosynthesis is a reaction that releases molecular oxygen, with the emergence of fermenting autotrophs this gas became available. Few organisms then developed aerobic respiration using O2, a highly efficient method to produce energy.