Oparin’s hypothesis

According to F. Dyson (1985) (see Sect. 8.5), Eigen has stood Oparin s hypothesis (first cells, then enzymes, and finally genes) on its head by reversing this sequence first genes, then enzymes, and finally the cell. Dyson finds the Eigen theory popular for two reasons ... 

The laboratory experiments of Miller (1953) proved Oparin s hypothesis, according to which the organic compounds necessary for the formation of the life were produced in a reducing atmosphere. 

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. 

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... 

Most scientists speculate, however, that the first organisms were bacteria, and most agree with Oparin s (1938) hypothesis that they were hetero-trophic, i.e. they obtained their energy by oxidizing organic compounds. Indeed, the first bacteria are viewed by some as being very similar to the anaerobic fermentative bacteria. 

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. 

Whereas most of the work discussed so far in this essay has dealt with the synthesis of well-defined biochemical species supporting the theory of chemical evolution as first proposed by A. I. Oparin, one of Oparin s major concerns has been to develop a hypothesis of precellular evolution and to experimentally demonstrate that specific biochemical reactions can occur within simulated precellular entities (coacervates). In an elegant experiment, using polynucleotide phosphorylase in coacervate droplets and the appropriate substrate in the external medium, he showed a continuous uptake of the substrate, a rapid internal synthesis of polynucleotides and a continuous release of phosphate to the external environment. His more recent concepts on evolution of probionts and the origin of cells were presented at the 4th International Conference on the Origin of Life held in Barcelona, Spain, in 1973. Experimental models involving microspheres made of polymers of amino acids have been developed by S. W. Fox and coworkers > and other investigators. 

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