The Origin of Life on Earth

Evidence from neighboring bodies in our solar system indicates that precursors for building biological molecules were present on the primitive earth. Energy in the form of sunlight, lightning, and heat from the earth's crust was also present.

Stanley Miller used a lab apparatus to demonstrate how life could have originated from the simple molecules that likely existed on the primitive earth. Miller discharged an electric spark simulating lightning into a mixture of hydrogen, methane, ammonia, and water that was thought to resemble the primordial composition of the atmosphere. In the water receptacle, designed to model an ancient ocean under abiotic conditions, amino acids and other small molecules were formed.

This animation (Audio - Important) describes the Miller-Urey experiment..

It is thought that a molecule called RNA (Ribonucleic Acid) may have preceded DNA and been the first genetic material because RNA can assemble spontaneously. How the switch from RNA to DNA might have occurred is not known. One possible sequence is shown in this diagram (read from the bottom up)

REVIEW: Experiments like those first performed by Stanley Miller in 1953 demonstrated that
Answer many of the lipids, carbohydrates, proteins, and nucleotides required for life can form under abiotic conditions.