The iron–sulfur world hypothesis is a set of proposals for the origin of life and the early evolution of life
Oparin suggested that orgainc compounds could have undergone a series of reactions leading to more and more complex molecules. He proposed that molecules formed coacervates. These coacervates were able to absorb and assimilate organic compounds from the environment in a way reminiscent of metabolism. They would have taken part in evolutionary processes, eventually leading to the first lifeforms. Haldane's theory is similar, it proposed that the primordial sea served as a vast chemical laboratory powered by solar energy. The atmosphere was oxygen free, and the combination of carbon dioxide, ammonia and ultraviolet radiation gave rise to a host of organic compounds. The sea became a 'hot dilute soup' containing large populations of organic monomers and polymers
- Stanly Miller placed a vial with a mixture of ammonia and cyanide, chemicals that scientists believe existed on early Earth in 1972. - The mixture of ammonia and cyanide, normally colorless, had deepened to amber, highlighting a web of cracks in the ice. - This meant that complex polymers made up of organic molecules
In stimulated ancient seawater, clay forms a hydrogel (a mass of microscopic spaces capable of soaking up liquids). Over billions of years, chemicals confined in those spaces could've carried out the complex reactions that formed proteins, DNA and eventually all the machinery that makes a living cell work.
The theory of RNA World hypothesis is a possible answer to the question of how life originated. Its believed that self replicating RNA may have formed in early Earth in volcanic vents in the Ocean floor, on clay clumps or carried on asteroids from mars, allowing life to be created.
The panspermia hypothesis states that the "seeds" of life exist all over the Universe and are responsible for originating life on Earth. It is significant as it suggests that the molecules that created life didn't form on Earth but from the universe. Professor Crick and his colleagues concluded that the scientific evidence was 'inadequate at the present time to say anything about the probability'.