Stanley L. Miller and Harold C. Urey's showed how the organic molecules arose. They assembled an
atmosphere similar to that thought to exist on early earth (this had molecules like ammonia, methane and hydrogen sulphide, but no oxygen) over water. They maintained a temperature just below 100°C and passed sparks through the mixture of gases to simulate lightning. By the end of a week it was observed that 15% of the carbon (from methane) had been converted to simple compounds of carbon including amino acids which make up protein molecules.
