Oparin—Haldane hypothesis

Stanley Miller at the University of Chicago more than 50 years ago. This experiment (in fact, of course, many were carried out prior to the successful one) is probably as well known as the Wohler synthesis of urea Miller s doctoral supervisor, Harold Urey (winner of the Nobel Prize in 1934), had suggested to Miller that he simulate a reducing primeval Earth atmosphere (as required by the Oparin-Haldane hypothesis) to electrical discharges and see what happens . Urey apparently expected that such an experiment would lead to a huge variety of organic compounds. 

In the study of chemical evolution we are interested in the path by which molecules of biological significance could have been formed on the earth before the appearance of life. We have therefore examined the action of electric discharges on the presumed primitive atomsphere of the earth. Three different sets of experiments were performed (1) with methane, ammonia, and water (2) with methane and ammonia (3) with methane alone. Several molecules of biological significance have been synthesized. In some instances polymerization appears to have taken place. These results may be relevant to the Oparin-Haldane hypothesis of chemical evolution. 

The first hypothesis of this type for explaining the appearance of life on our planet was due to the Russian biochemist Alexander I. Oparin and independently by the British evolutionary biologist John B. S. Haldane, and is more than 50 years old. The basic idea in the Oparin-Haldane hypothesis is that the atmosphere contained only reducing molecules mentioned previously under (2), during the first few thousand million years of its existence. 

Facts supporting the Oparin-Haldane hypothesis have now accumulated. The ancient atmosphere has been reconstructed in closed volumes. After some weeks of discharge between electrodes, new molecules were discovered, some of which occur in living systems (Stanley Miller and Harold Urey). The conclusion is that a molecular evolution may have started in a primordial soup of this type, where some large and stable molecules are created in relatively high concentrations. 

Some of the views on the evolution of biochemical capabilities and pathways are now widely shared and these will be summarized here briefly because they are necessary for the arguments that follow. According to the Oparin-Haldane hypothesis all major structural types that compose contemporary cells were created chemically before life began. From... 

Up until the origin of RNA molecules, Dyson describes the logical consequences of the initial hypotheses, and his scheme is therefore a coherent theory of chemical evolution. But the mathematical model does not say anything about the subsequent integration of RNAs and hosts, and on this point Dyson resorts to a supplementary conjecture. He proposes that primitive RNAs invaded their metabolic hosts, and used them for their own replication, like viruses do, which is exactly Haldane s hypothesis. Dyson concludes therefore that, after Oparin s metabolism stage, came Haldane s replication stage, and his final scheme becomes metabolism first, replication second . That RNAs... 

---