How could organic molecules have formed from inorganic materials on Earth?

The ancient atmosphere consisted of methane, ammonia, carbon monoxide, carbon dioxide, nitrogen, and water, but lacked free oxygen. There was probably intense lightning and ultraviolet (UV) radiation.

Without corrosively reactive molecular oxygen present to react with and degrade them, organic molecules could form and remain.

Then, these molecules served as monomers (building blocks) to form more complex molecules, such as amino acids and nucleotides.

The joining of these monomers produced polymers with the ability to replicate, store, and transfer information.