The basic idea is that:-
- In the primitive Earth various chemical reactions took place, this could have happened anywhere with an energy source. These reactions might have taken place in the oceans under the influence of sunlight, round hydrothermal vents or in caves.
- Eventually by chance self-replicating molecules formed, these molecules were much simpler than modern organic molecules.
- The probability of any individual atom becoming part of a self-replicating molecule by chance was unimaginably small.
- Unimaginably vast numbers of atoms and molecules were reacting chemically with each other.
- The probability that somewhere among these vast numbers of chemical reactions self-replication would develop was high.
- Self-replicating molecules proliferated, some replicated more successfully than others, replication was sometimes imperfect and new types of self-replicating molecules emerged.
- Natural selection and evolution started, more efficient self-replicators out competed others.
- Systems of self-replicating molecules evolved with individual molecules combining symbiotically to help the whole system replicate.
- Over very long periods of time systems of self-replicating molecules evolved to become living organisms.