|Evolution in the News - June 2007|
|by Do-While Jones|
Dr. Stanley Miller was still looking for the origin of life when he died.
We truly had genuine respect for Stanley Miller, and the work that he did, and were saddened by news of his death on May 20, 2007. Unfortunately, his life work was usually reported inaccurately. His LA Times obituary is typical.
Stanley Miller, the UC San Diego chemist who was the first to demonstrate that the organic molecules necessary for life could be generated in a laboratory flask simulating the primitive Earth's atmosphere, died Sunday from heart failure in a hospital in National City. He was 77. 1
He certainly was not “the first to demonstrate that the organic molecules necessary for life could be generated in a laboratory flask simulating the primitive Earth's atmosphere,” but that is what is commonly reported in the popular press, and in public school textbooks. A somewhat more accurate report of his real contribution can be read at a University of California at San Diego web site article honoring his 70th birthday. 2 He worked at UCSD until shortly before his death. We encourage you to read about his work there. 3
Dr. Miller’s significant contribution to science is that he, more than anyone else, is responsible for the origin of exobiology research (abiogenesis). His famous 1953 experiment showed that organic molecules could be formed rather quickly and easily. The organic molecules he produced were neither “the organic molecules necessary for life,” nor were they produced in an environment “simulating the primitive Earth's atmosphere,” as is commonly reported. But his initial experiment was significant because it encouraged many other scientists to perform countless experiments about the ways in which organic compounds could be naturally produced.
He spent his whole life looking for ways to produce organic molecules that could have produced the first living cell, but was unsuccessful. Many other lesser men have also tried, and failed, to demonstrate a plausible way in which life may have originated naturally. Their failures have less impact because they aren’t men of Dr. Miller’s caliber. But the fact that Dr. Miller searched so hard for so long without success is a good indication that there is no plausible way life could have originated naturally.
We would like to share with you portions of the last paper that Dr. Miller published. He submitted it on February 2, 2000. It appeared in the Proceedings of the National Academy of Science three months later. But first, let us give you some background.
There is much more to life than just some amino acids and proteins. For life to begin, all the chemicals have to have a method of reproducing themselves, and passing along genetic information to the offspring. Modern living things use deoxyribonucleic acid (DNA) to do this. But DNA is a much too complex molecule for it to have originated in the first living cell, and the biologic processes needed to decode it are much too complicated, too. Therefore, evolutionists have been looking for a simpler molecule than DNA that might have the required properties. One such candidate is ribonucleic acid (RNA), which spawned the “RNA world hypothesis.” But Dr. Miller wisely observed,
Numerous problems exist with the current thinking of RNA as the first genetic material. No plausible prebiotic processes have yet been demonstrated to produce the nucleosides or nucleotides or for efficient two-way nonenzymatic replication. 4
The discovery of the catalytic activity of RNA brought the concept of an RNA world into wide acceptance. However, the instability of ribose and other sugars, the great difficulty of prebiotic synthesis of the glycosidic bonds of the necessary nucleotides, and the inability to achieve two-way non-enzymatic template polymerizations have raised serious questions about whether RNA could have been the first genetic material, although there are dissenting opinions. 5
Dr. Miller recognized that the RNA world hypothesis was a non-starter. So, he was looking for another way. In his final paper he said,
One proposal offers peptide nucleic acids (PNA) as a possible precursor to RNA because PNA binds DNA and forms double and triple helical structures that are related to the Watson-Crick helix. 6
Peptide nucleic acid (PNA) is a promising precursor to RNA, consisting of N-(2-aminoethyl)glycine (AEG) and the adenine, uracil, guanine, and cytosine-N-acetic acids. However, PNA has not yet been demonstrated to be prebiotic. We show here that AEG is produced directly in electric discharge reactions from CH4, N2, NH3, and H2O. … Preliminary experiments suggest that AEG may polymerize rapidly at 100oC to give the polypeptide backbone of PNA. The ease of synthesis of the components of PNA and possibility of polymerization of AEG reinforce the possibility that PNA may have been the first genetic material. 7
He admits that, “PNA has not yet been demonstrated to be prebiotic.” In other words, there is no evidence that PNA existed before life began. But, for PNA to exist, AEG (and adenine, uracil, guanine, and cytosine) would have had to exist. He was looking for a way to produce AEG naturally as a stepping stone to PNA.
In his 1953 experiment, he used an atmosphere consisting of methane, hydrogen, ammonia, and water vapor. In his last reported experiment he substituted nitrogen for hydrogen. That’s reasonable because today’s atmosphere is 79% nitrogen and 0% hydrogen. If the present really is the key to the past, then it is reasonable to assume life began with nitrogen in the atmosphere (and water vapor, too). But the only place you are likely to find methane and ammonia in the air today is near a diaper pail.
Notice, too, that his simulated atmosphere is still oxygen-free. All origin of life experiments use oxygen-free atmospheres. That, of course, is because oxygen would immediately break down any AEG his experiment produced. The only reason for believing the Earth ever had an oxygen-free environment is because organic compounds could not possibly have originated naturally in the presence of oxygen.
His last experiment showed that a spark in an atmosphere radically different that Earth’s present atmosphere could produce AEG at 100o C (the boiling point of water). He concludes that if AEG existed, it might possibly have helped in the natural formation of PNA, which might somehow have acted sort of like RNA in some sort of unknown replication process. But let us not unfairly put words in his mouth. Here is the concluding paragraph of his last published paper.
|Polymerizability and Suitability as the First Genetic Material. The above results show that the components of PNA are likely prebiotic compounds and, under favorable conditions, could be major constituents of the primitive milieu. Still to be worked out are the prebiotic syntheses of the monomers and mechanisms for their polymerization, but prebiotic polymerizations are imposing problems for any potential early genetic system. Our preliminary experiments indicate that AEG polymerizes readily at 100oC to give AEG oligomers and does so much more efficiently than mixtures of -amino acids at higher temperatures. Although PNA also has stability problems of its own, they are highly sequence-dependent and may be alleviated by blocking or acetylating the N terminus. There is also the more difficult problem of PNA replication, which may be complicated by cyclization of the monomers. Nevertheless, this demonstration that the PNA components are prebiotic suggests the possibility that PNA or similar molecules may have been the first genetic material. However, other possibilities need to be considered because there may be other backbones and bases that were more abundant and more efficient for prebiotic replication. 8|
Just in case you didn’t follow all that, he found a way to produce AEG which might have allowed PNA to form through a process that is “still to be worked out” in spite of “imposing problems for any potential early genetic system.” But, if it did form naturally it might have disintegrated before it had a chance to replicate because “PNA also has stability problems of its own.” And then, “there is also the more difficult problem of PNA replication.”
So, after all that work, Dr. Miller never found what legend says he did—the building blocks of life. Some might say he wasted his whole life on a wild goose chase, but we would disagree. We say that if there had been a wild goose, Dr. Miller would have caught it. He left behind a wonderful legacy of research showing the insurmountable difficulties that prevent life from arising naturally.
Hopefully, years from now, history will correct the errors of the careless popular press. Dr. Miller should not be celebrated for being “the first to demonstrate that the organic molecules necessary for life could be generated in a laboratory flask simulating the primitive Earth's atmosphere.” He should be celebrated for being the one who most conclusively showed that the organic molecules necessary for life could not have been generated in the primitive Earth's atmosphere through his exhaustive research down every blind alley.
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Thomas H. Maugh II, LA Times Staff Writer, May 24, 2007, “Stanley Miller, 77; chemist was a pioneer in studying the origins of life”
4 Kevin E. Nelson, Matthew Levy, and Stanley L. Miller, PNAS, April 11, 2000, vol. 97, issue 8, “Peptide nucleic acids rather than RNA may have been the first genetic molecule”, pages 3868-3871