Primeval soup re-brewed, as reported in Scientific American, 28 March 2007. Jeffrey Bada of Scripps Institute of Oceanography, California, has revisited the famous "origin of life" experiment made famous by Stanley Miller 1953. Miller's experiment produced amino acids, which are essential building blocks for living cells, by exposing a mixture of methane and ammonia to a regular source of electric sparks. This was meant to be a simulation of earth's primitive atmosphere in order to test the theory that organic molecules can arise spontaneously from chemical reactions produced by lightning strikes through an atmosphere of simple molecules.

Over the years scientists changed their minds about the composition of earth's early atmosphere and by 1983 had decided that it was a mix of carbon dioxide and nitrogen, rather than methane and ammonia. Miller did the experiment again in 1983 using this combination of gases, but produced hardly any amino acids. Bada has found this version of the experiment produced nitrites, chemicals that destroy amino acids as soon as they form and turn the water acidic, further inhibiting the formation of amino acids. Bada proposed that the primeval earth would have contained iron and carbonate minerals, which would have neutralised the nitrites. He has now carried out the experiment again with chemicals that neutralise nitrites and produced amino acids.

Bada's results have added to an ongoing debate over whether life arose from chemicals that arose on earth alone or were chemicals from meteors and comets necessary to get life started. Christopher Chyba, an astrobiologist at Princeton University commented, "That would be a terrific result for understanding the origin of life, and for understanding the prospects for life elsewhere."

Editorial Comment: It is interesting that school textbooks always describe the 1953 version of Miller's experiment, even though scientists have long ceased believing in Miller's original ingredients as a model of the original earth atmosphere. Bada may have produced amino acids with his new brew, but he has the same problem that Miller had with the original brew. Each amino acid comes in two shapes that are chemically the same but different in structure, in the same way right and left hands are mirror images of one another. The amino acids in living cells are all left handed. Chance random chemical processes, such as occur in primeval soup experiments, always produce a mixture of right and left handed amino acids. The only known ways of producing pure left handed amino acids involve creative manipulation of the system, i.e. intelligent design. Furthermore, if you leave a solution of pure amino acids to chance random processes it will slowly but surely change into a mixture of right and left handed molecules. This process is called amino acid racemisation and occurs after living things die. Miller and Bada have only produced the molecules of death and have done nothing to explain the origin of life. (Ref. chirality, abiogenesis, primordial)

Evidence News 13 June 2007


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