How origin of life started?

The deep-sea vent theory suggests that life may have begun at submarine hydrothermal vents spewing key hydrogen-rich molecules. Their rocky nooks could then have concentrated these molecules together and provided mineral catalysts for critical reactions. 

The origin of life on Earth is a scientific problem which is not yet solved. There are many ideas, but few clear facts.

Most experts agree that all life today evolved by common descent from a single primitive lifeform. It is not known how this early life form evolved, but scientists think it was a natural process which happened about 3,900 million years ago. This is in accord with the philosophy of naturalism: only natural causes are admitted.

It is not known if metabolism came first or genetics. The main hypothesis which supports genetics first is the RNA world hypothesis, and the one which supports metabolism first is the protein world hypothesis.