Answer: Reproducing molecules evolved into living molecules by chemical processes.
In 1952, Stanley Miller and Harold Urey conducted an experiment to observe how complex organic molecules might have developed on early earth. They believed that the early earth atmosphere would be composed of methane, ammonia, water vapor and hydrogen gas. They sealed these gases in an air tight container. Later, they exposed the gases with an electric spark for a week. They found that a reddish brown substance covered the wall of the container from inside. This brownish substances consisted of amino acids. The amino acid is the basic biological unit found in all living organisms. The early earth atmosphere was reducing and warm, this condition could be responsible for generation of amino acids which are reproducing molecules formed by chemical processes occurring on early earth.
