What hard evidence do we have today for a theory of the origin of life?

The first area is comparative biochemistry along the lines we have been following. The more we learn, the more the Oparin-Haldane ideas make sense.

In addition, we have geological evidence from the Earth's own history, including evidence for a primitive reducing atmosphere and fossil remains of primitive microorganisms. These fossils allow us to assign dates to the various biochemical steps in the origin of life.

Finally, laboratory demonstrations, point out the feasibility of the nonbiological synthesis of the molecules of life, and of the formation of simple, organized chemical systems.

These considerations cannot prove the theories about what actually happened billions of years ago, but they can give them plausibility.