Life has evolved from complex combination of chemical substances. Presence of methane on various celestial bodies indicates that the primitive atmosphere on earth was highly reducing in nature because of presence of methane, ammonia, hydrogen and water vapour. Compounds formed after combination of these elements underwent further combinations to form complex compounds. Different forms of those complex compounds had laid the foundation of life. In due course of time, primitive life forms went through a prolonged phase of struggle and competition to create the living world which we witness today.
