The most accepted theory about origin of life is the chemosynthetic theory. Earth’s early environment was favourable for the formation of organic molecules from simple inorganic materials. Coacervates are believed to have been membrane–bound molecular aggregates capable of growth and budding. It is believed that life originated some 3.5 billion years ago on this earth. The environment and the forms of life of the past were quite different from those of today. Evolution is the gradual unfolding of living forms from the earlier simpler forms into the complex ones. It was in operation in the past, it is operating at present and will continue do so in the future. Chief evidences in favour of organic evolution come from comparative anatomy, embryology, palaeontology and molecular biology.
