"Scientists are not close to knowing the exact processes that took place on the earth which led to the origins of life. They may never know the exact answer because the evidence for this very primitive life has probably been destroyed by the more efficient life which evolved from it. But scientists have made important progress in understanding the types of chemical processes that may have led to the origins of life.
A simple example may help to illustrate this difference between knowledge of the exact answer and possible answers to the question. A friend of mine called to tell me that he is in San Diego; he then asked me to deduce the exact route he followed in getting there from Troy, NY. From the time of my last encounter with him I can guess whether he traveled from Troy by airplane, or car. Then I can try to decide which airline he took or which highways he followed, but I will never know unless I can gain access to the computer systems of all the airlines and can find his reservation, or can travel all the routes from Troy to San Diego, stopping at gas stations and asking if they remember seeing this person. Short of having this detailed information, I will have to be satisfied with developing plausible scenarios based on my knowledge of the starting and ending points and the approximate time it took him to make the trip.
"We are in a similar predicament with our understanding of the origin of life. Since we don't have detailed information on the exact steps we will have to be content with developing plausible scenarios based on information concerning conditions on the early earth around the time life originated nearly four billion years ago. One plausible scenario holds that the first life on earth was based on ribonucleic acids (RNA), a simpler chemical cousin of DNA. Many researchers have focused on RNA because it can store genetic information and it can catalyze reactions; these are essential processes in living systems. In this scenario, it is proposed that RNA, a polymer (long-chain molecule), arose from the gradual stringing together of repeating chemical units, known as monomers, that naturally arose on the primitive earth.
"Recently it has been shown that it is possible to form RNA from monomers on the surfaces of clays, which can catalyze, or chemically assist, the polymerization reaction. Experiments done in test tubes (in vitro) have shown that RNA with one type of catalytic activity can evolve to an RNA with different catalytic properties. These two sets of experiments suggest that it may be possible to demonstrate how clay minerals could have permitted the formation of complex RNA molecules that are capable of evolving in form. If this inference is correct, then the research provides support for a plausible scenario for the origins of life. But, as with the question concerning the route my friend took from Troy to San Diego, we will never know for sure. Just as my friend may have reached San Diego by flying east to Europe and Japan, life may have evolved by an equally circuitous route.
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