Primeval soup
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The phrase primeval soup is attributed to the Russian biologist Aleksandr Oparin. In 1924 he put forward a theory of life on Earth developing through gradual chemical evolution of carbon-based molecules in primeval soup.
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[edit] Experimental demonstration
In the early 1850s at the University of Chicago Stanley Miller demonstrated the primeval soup model for the origin of life on Earth. He passed a spark of electricity through a glass chamber filled with water, methane, ammonia and hydrogen (meant to simulate conditions on the young earth). A week later, paper chromatography showed several amino acids and other organic molecules had formed. The model for the origin of life said these molecules were formed in the atmosphere, rained into the ocean, then combined to make proteins, nucleic acids and the other molecules of life.
[edit] Problems with the theory
A central problem is explaining the synthesis of polymers because hydrolysis in the ocean would break them up. Also abiotic synthesis produces a mixture of L and D enantiomers which inhibit polymerization of each other. It was then theorised that early polymers assembled on solid minerals such as clay. Polynucleotides and polypeptides of about 50 units have been made in the laboratory in this way.
[edit] Subsequent work
Christopher Wills and Jeffrey Bada at the University of California, San Diego said small organic molecules could react with larger organic molecules in oily films on beaches and in tide pools. Some molecules which remained in the films and were able to resist being washed away were "selected" according to the rules of natural selection. Gradually, more complex systems developed which possessed primitive biochemical functions. The theory says materials could replicate by genetic mechanisms which were simpler than RNA or DNA.
Ribozymes made in the laboratory, but not found in nature, can catalyze the assembly of short oligonucleotides into exact complements of themselves, according to the rules of base pairing. It is possible that life began with RNA before proteins began to act as enzymes and help make DNA the basis of the genetic code. Supporting evidence for this notion is the importance that ribose plays in ATP, NAD, FAD, coenzyme A, cyclic AMP and GTP.
