‘How did life come into existence?’ is a question mankind has tried to answer in several ways. Religious texts have offered answers that are often unverifiable or inconsistent. Just like in the case of any other area of questioning, science has answered the question in a methodical way and tried to explain the origins of life based on the existing scientific knowledge in a coherent and consistent manner. Life is so complex in its physical and chemical form that till date existence of life at any place in the universe other than earth is not confirmed. But the explanation of the origin of life on Earth that science has derived, is that although rare, the existence of life elsewhere in the universe is not impossible.
Life in its simplest form consists of nucleotides that form the basis of nucleic acids (like DNA, RNA), amino acids that form the building blocks of proteins which in the presence of other chemical species function as one to form life. So if we can prove the chemical and physical conditions of the planet earth in its early days can contribute to the formation of these basic chemical forms we have answered the question of how life on earth came into existence.
The chemical nature of the new born earth is referred to as primordial soup. This consisted of all the chemical species required for formation of the chemical building blocks of life. Along with these chemicals, there was intense lightning activity on earth due to the volcanic activity and other violent weather phenomena. As the temperatures cooled down there was condensation and formation of liquid water. Miller and Urey have simulated these conditions in the laboratory and found out that these conditions result in the formation of building blocks of life.
The experiment consisted a container where all the basic chemicals present in the primordial environment (water, ammonia, methane and hydrogen) were taken. The container has an influx of water vapour and the water going out of the container is sampled for its chemical nature. There were also electrodes inserted into the bowl of chemicals taken to simulate lightning, like the electrostatic charging and discharging processes we have learnt during our Physics tuition class. After days of running the experiment continuously, basic chemicals like amino acids were formed. The experiments showed that under reducing atmosphere nucleobases (building blocks of DNA and RNA) can also be formed. These experiments explain how the early pre-biotic atmosphere resulted in the formation of building blocks of life which can further organise and form complex lifeforms. Thus the origin of life is not a mystery but a question within the reach of current science.