(N/A) British scientist,$J$.$B$.$S$. Haldane,suggested that life originated from simple inorganic molecules. He believed that when the earth was formed,it was a hot gaseous mass containing elements such as nitrogen,oxygen,carbon,and hydrogen. These elements combined to form molecules like water $(H_2O)$,carbon dioxide $(CO_2)$,methane $(CH_4)$,and ammonia $(NH_3)$.
After the formation of water,the earth's surface slowly cooled,and the inorganic molecules interacted with one another in water to form simple organic molecules such as sugars,fatty acids,and amino acids.
The energy for these reactions was provided by solar radiation,lightning,and volcanic eruptions. This was proved by the experiment of Stanley $L$. Miller and Harold $C$. Urey in $1953$. They took a mixture of water $(H_2O)$,methane $(CH_4)$,ammonia $(NH_3)$,and hydrogen gas $(H_2)$ in a chamber and passed sparks through this mixture using two electrodes. After one week,$15\%$ of the carbon from methane was converted into amino acids,sugars,etc. These organic molecules polymerized and assembled to form protein molecules that gave rise to life on earth.