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Primordial Soup Experiment

07labcoatS.jpg So much of the work until the early 1950's that was done in laboratories was of a rather hypothetical nature. Indeed even possibly speculative, highly controversial, but nevertheless quite speculative. Then, in 1953 there was a major breakthrough. Stanley Miller, a student of Harold Urey's at the University of Chicago, published a two page paper in Science in which he did the experiment. If one goes back and reads the early literature, translations of Oparin, Haldane, and indeed one of the interesting things is that Harold Urey speculated on the composition of the early atmosphere on the primitive earth. So Miller was in good company working with Harold Urey. And Miller, what he did was, he did the experiment. I'll say "The" with capital letters. The experiment to take the speculation, the hypothesis, and put it to the test.

08tubesS.gif He created this vessel and in that vessel there was no oxygen. Molecular oxygen was excluded. And he used gasses that were thought to occur on the primitive earth at the time, early in the history of the earth: hydrogen, methane, ammonia, and water... a carbon source, a hydrogen source, a nitrogen source and an oxygen source. And he had an electric spark in this vessel. After several days, it started to be covered with some brown material, the liquid became brownish in color. When the material in that vessel was analyzed, there was found to contain amino acids.

So, here is the experiment that basically says you can take non-living material, material that was on the early earth--hydrogen, methane, ammonia, and water--and you can provide an energy source and you can produce organic compounds. You can produce amino acids, building blocks of what we know today that are proteins. So this is the experiment that took speculation into the laboratory. And since that time, since 1953, there have been numerous experiments around the world using different model gasses, producing a variety of organic compounds. I'm not an organic chemist and my research area does not include chemical evolution. My interests are mainly once life evolved. What does that tell us? And once it appears in the fossil record, what does that tell us about life's origins?

My research interests are also: "What were the chemical/physical conditions on that primitive earth that would allow for or prevent, inhibit, chemical evolution?" It's from this perspective, from not the test tube tapping experimental perspective but from a different perspective that I want to draw your attention to some of the very exciting things that are going on in studies of the origin of life. This goes back to astrobiology. Astrobiology is extremely inter-disciplinary, extremely multi-disciplinary. It takes researchers in the traditional fields of science and indeed we hope to include other fields like social sciences, religion, to bring them in under this umbrella of astrobiology and try to get at some of the exciting questions. The origin of life is probably one of the most exciting questions facing science. To put that in the broad perspective, to understand the history of the universe, etc., as well as what went on on Earth billions of years ago is a challenge before us.

Let us go back to Stanley Miller's experiment because he's so important. He found that at least 10 percent of the carbon was converted into a small number of organic compounds and about two percent went into amino acids. Hydrogen, cyanide, and aldehydes were also produced. Glycine was the most abundant amino acid produced. You go back to Darwin's 1871 letter, the experiments of Stanley Miller and the first one reported in 1953 and subsequent experiments. It appears that proteins, or at least getting amino acids, getting them to polymerize, you have all the basic structure there that goes on. But that's only one half of life. What about the replication that is so important for life and evolution?

Juan Oró, in 1961, took some of the materials that were produced in the Miller experiments and he took hydrogen cyanide, one of these compounds produced, along with ammonia and left out the aldehyde. So he kind of organized the experiment in a certain way. He produced some amino acids but he also got some adenine, one of the nitrogen containing bases. Later experiments by him and others were actually able to produce the other nucleic acid bases. So now we see there's another area of chemical evolution experiments going on to get at replication. Also, it was found that sugars could be produced. Formaldehyde is one of these monomers produced in the Miller experiments and other experiments. The formaldehyde could polymerize to form a ribose. And indeed, in various kinds of experiments, ribonucleotides are more readily synthesized than the dioxyribonucleotides. Therefore, it started to appear that maybe, if that's the case, the ribonucleotides, that RNA may have appeared early, that the early world was an RNA world.

But this leads to a paradox because today nucleic acids are only synthesized with the help of proteins and the proteins are synthesized only if their corresponding nucleotide sequence is present. So we have sort of a chicken and egg problem. It's improbable that proteins and nucleic acids arose spontaneously, at the same time and at the same place. It seems implausible to have one without the other.

In 1986 Tom Cech discovered something called a riboenzyme, basically, enzymes made of RNA. They could do little more than cut and join preexisting RNA, but until then proteins were thought to carry out all the catalytic activities in an organism. So, now we see since 1953, since the experiment of Stanley Miller, some extremely interesting directions in which chemical evolution has moved. A great deal of information, a great deal of organic compounds have been produced yet no self replicating life or organism or cell has yet been produced in the laboratory. And that's often a criticism that is aimed at chemical evolution studies by the creationists: "Well, why haven't you produced life in the laboratory?" But it's only been 44 years since Stanley Miller's experiment was published in Science. And although there may have been and still are many laboratories around the world that are involved in experiments to produce organic compounds from various kinds of gases that may have existed on the primitive earth, it's not like what probably occurred on the early earth back four or more billions years ago. Forty four years isn't a lot of time.

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