The door at the front of the courtroom opened and the judge entered. A court officer said: "All rise," and, then, a short time later: "Please, be seated."

"You may continue with your examination of the witness, Mr. Mayfield," Judge Arnsberger directed. "I should remind the witness that he is still under oath."

"Dr. Yardley, I believe," indicated the prosecutor, "you were talking about meteorites and carbonaceous chondrites before the recess. Would you continue on with your testimony, please."

"Actually," the professor stated, "I was just about to begin talking about something else when the recess was announced. As I suggested earlier in my testimony, meteorites, comets and interplanetary dust particles are only one approach to explaining the presence of various kinds of hydrocarbons, both simple and complex, in the prebiotic environment of early Earth history. The other approach, to which I will now turn, concerns the chemical processes which are believed by evolutionary biologists to have been operating prior to, but which eventually brought about, the advent of biological organisms.

"Serious experimental work in the area of prebiotic chemistry has been going on for nearly forty-five years in laboratories all over the world. Symposia and conferences dedicated to this subject take place on a regular basis, and, in addition, there are academic journals that publish articles dealing with virtually every facet of the prebiotic chemistry in which life is believed to have had its origins.

"Obviously, I cannot possibly present all of that material at this time. What I can do, however, is to try to provide some of the broad brush strokes of the picture being painted by researchers.

"Although a few scientists, such as Alexander Oparin, in the Soviet Union, and J.B.S. Haldane, in England, had been doing work on this topic during the 1930s, many people cite the early-1950s work of Stanley Miller and Harold Urey at the University of Chicago as marking the real beginning of serious investigation of the conditions necessary for the chemical origins of life. They were the first to put things to the test under laboratory conditions.

"In an oft-cited, classic experiment, Miller gathered some gases, such as methane (CH₄) and ammonia (NH₃), believed to be present in the early Archean era atmosphere, subjected these gases to a continuous spark discharge, which was intended to simulate the action of lightening, and examined the results after a number of days. The laboratory procedure had generated a variety of amino acids, some of which are found in living organisms and some which are not present in life on Earth.

"Amino acids are complex hydrocarbons. They consist of three parts.

"One part is a carboxyl group, having a formula of COOH. A second component is an amino group with a formula of NH₂.

"The third aspect of the amino acid is a side chain. This varies, in a unique way, with each, different amino acid.

"Some 16-17 years after Miller's experiment, the Murchison meteorite was found in 1969, and scientists were able to demonstrate a number of similarities between the products of Miller's experiment and the hydrocarbons found in the meteorite. For instance, they discovered that the kind and quantities of amino acids found in the Miller experiment were very, very similar to the kind and quantities of amino acids found in the meteorite.

"In any case, by 1953, Miller had produced the first experimental evidence that natural chemical processes could produce complex organic compounds which are fundamental to life on Earth. Over the next forty-odd years many other experimental results would be forthcoming from Miller and other researchers.

"In one series of experiments, Miller and Urey discovered that roughly 10% of the carbon molecules contained in the gases of their experimental set-up eventually were converted into known organic compounds. Furthermore, as much as 2% of this converted carbon was involved in the generation of amino acids within the experimental apparatus."

The prosecutor, Mr. Mayfield, who had been listening intently to the professor, suddenly came to life, so to speak, and said: "Dr. Yardley, earlier you had indicated that an oxidizing atmosphere - in other words, an atmosphere composed of, say, oxygen, which strips other compounds of hydrogen, tends to interfere with chemical processes that build complex hydrocarbons from simple hydrocarbons. Is there a name for the sort of atmosphere which is conducive to the generation of complex hydrocarbons from simple ones?"

"Yes," he replied, "the kind of atmosphere to which you are referring is known as a reducing atmosphere. Such an atmosphere is dominated by molecules that can donate hydrogen atoms, or, more precisely, electrons, to other substances.

"Methane and ammonia, the gases used in Miller's experiment, are both considered to be relatively good reducing agents. This means they tend to be involved in chemical reactions involving, to simplify things somewhat, the donation of some of their hydrogen atoms or electrons, which then interact with other hydrocarbon compounds to help make possible, under the appropriate conditions, the formation of even more complex hydrocarbon molecules.

"In one sense, all organic compounds are actually different gradations of reduced forms of carbon. Generally speaking, this is due largely, although not necessarily always, to the presence of hydrogen in such compounds.

"Creating different kinds of reducing atmospheres under experimental conditions, investigators were able to produce a variety of amino acids. Glycine, valine, alanine, proline, glutamic acid and aspartic acid all have been generated through different kinds of electric discharge experiments.

"In another experiment, when sunlight was passed through a solution of paraformaldehyde (CH₂O)₃, ammonia (NH₃), and ferric chloride, the amino acids asparagine and serine were produced. On the other hand, when solid ammonium carbonate was exposed to high doses of gamma rays, small quantities of the amino acid glycine, along with formic acid (HCOOH), resulted.

"In 1961, another scientist, Juan Oro wondered if amino acids could be generated under laboratory conditions if one used chemical processes which were even simpler than those involved in Miller's earlier experiments. Previous experiments had proven that if one exposed a mixture of hydrogen, nitrogen and carbon monoxide gases to a spark discharge, the reaction would yield hydrogen cyanide (HCN), which is a very reactive intermediate compound.

"Oro combined hydrogen cyanide with ammonia (NH₃) and water (H₂O). This chemical reaction produced a number of different amino acids, just as the Miller experiment had.

"In addition, among the product residues of his experiment, Oro discovered something else. This molecule was a purine, a nitrogen-containing base of considerable importance.

"The particular purine found by Oro is known as adenine. This molecule is one of two purine bases having a general formula of C₅H₄N₄, and three pyrimidine bases, each of which has a general formula of C₄H₄N₂. When any of these are combined with either of the pentose sugars, ribose or deoxyribose, together with a phosphate group, then, RNA or DNA is produced.

"Adenine is also one of the components of adenosine triphosphate. This latter molecule is one of the fundamental energy-providing compounds in most organisms.

"In addition to adenine, a number of other useful products could be produced by means of reactions involving hydrogen cyanide. These products included a variety of intermediate precursor molecules that constitute steps on the way to purine- or pyrimidine-formation, and the products of the reactions included, as well, a number of pyrimidine base molecules which are found in the nucleic acids of some, but not all, living organisms.

"Subsequent experiments demonstrated the possibility of generating, through natural chemical processes, the other nucleic acid bases- namely, uracil, cytosine, guanine and thymine, that are found in the vast majority of organisms on Earth. These reactions also started with hydrogen cyanide (HCN), but they required, as well, the presence of two other simple carbon compounds: cyanogen (C₂N₂) and cyanoacetylene (HC₃N), which are believed to have been present on the prebiotic Earth.

"Still other experiments were able to demonstrate that the pentose sugar, ribose, an important component of RNA, could be produced quite easily. This chemical process merely involved a series of spontaneous reactions involving molecules of formaldehyde CH₂O.

"Again and again, scientists were showing, experimentally, the possibility of starting with simple compounds and combining them to produce complex hydrocarbons. More importantly, these products were not just arbitrary molecules, but, rather, they were fundamental building blocks of compounds, such as proteins and nucleic acids, that are crucial to the life process.

"Researchers felt their laboratory experiments were recreating the conditions of prebiotic Earth and demonstrating that chemical reactions important to the origins of life would occur spontaneously. The whole process was relatively simple and straightforward.

"Initially, for example, atmospheric gases, such as methane and ammonia, would react together to generate a variety of simple hydrocarbons, like hydrogen cyanide and molecules known as aldehydes, which are compounds that contain a CHO group - such as formaldehyde (CH₂O). Next, the products of the first round of reactions- namely, aldehydes, hydrogen cyanide and ammonia, would enter into a second round of chemical interactions which would result in such intermediary products as amino nitriles. These products, in turn, would react with the water of the ocean to produce ammonia and amino acids, like glycine.

"People such as Sidney Fox were able to discover, experimentally, alternative methods for the prebiotic generation of various kinds of amino acids - methods which were different from the ones outlined by Miller and Oro. When Fox heated urea [CO(NH₂)₂] and malic acid (C₄H₆O₅) at temperatures of 150 degrees Celsius, he was able to obtain aspartic acid.

"Fox also was able to construct chains of amino acids through a process of thermal copolymerization or cooking. He referred to these chains of amino acids as 'protenoids' because they had certain structural similarities to the proteins found in living organisms.

"The recipe for thermal copolymerization of amino acids is fairly simple. One starts with some quantity of a given amino acid, such as glutamic acid.

"One places this quantity of amino acids in an oil bath and heats it at 170 degrees Celsius for an hour. When the timer goes off after an hour, one blends in a finely ground mixture of other kinds of amino acids.

"One heats this new mixture for an additional three hours at the same temperature as before. In addition, one heats it in an atmosphere of carbon dioxide.

"When the mixture has cooked for the requisite period of time, one allows it to cool under controlled conditions. When it is ready, one can examine the residue of this process and find polymerized or chemically linked sequences of amino acids of varying length and composition.

"Many of the protenoid polymer chains consisted of up to 100 amino acids. The nature of the bonds linking the amino acids varied in character, but some peptide linkages, the kind which occur in proteins in living organisms, were observed among these bonds.

"The thermal copolymerization process is capable of providing yields, by weight, of up to fifteen percent of the total mixture. These portions are considered by evolutionary biologists to be quite ample yields, although most of the rest of us may feel them to be too small to share with friends for a late night snack.

"There are variations on the foregoing recipe. Glutamine, another of the amino acids occurring in living organisms, is substituted for glutamic acid. Phosphoric acid is also added.

"In addition, one skips the step of pre-heating prior to the adding of other ground-up amino acids. Everything else stays, more or less, the same, yielding roughly similar results as before.

"One can play around with parameters such as the temperature and time, at which and for which, respectively, the mixture is cooked. One also can alter the ratios of the reactants and/or phosphoric acid to be used in the process.

"Experiments focusing on the manipulation of these variables have permitted protenoids with different kinds of character to be produced. For example, one can increase the percentage of neutral and basic amino acids that were incorporated into the polymerized chain.

"In 1977, a scientist by the name of Usher, demonstrated that when one used relatively low temperatures, one could generate phosphodiester bonds between the phosphate and ribose sugar portions of nucleic acids. This is an important step in generating fully functional DNA and RNA molecules.

"In 1978 Juan Oro showed, experimentally, that if one heated fatty acids, an important building block of lipids, and then dried them in the presence of phosphate and glycerol, one could synthesize simple phospholipids. Phospholipids are fundamental to the formation of cell membranes in most living organisms.

"Stanley Miller has synthesized a compound under prebiotic conditions which is known as pantetheine. This molecule has been observed to link amino acids in some organisms.

"Many of the compounds produced in these kinds of experiment are quite soluble in water. Researchers have hypothesized that these molecules, at one point or another, probably would have gone into solution in the ocean, and, later, they would have become part of more concentrated solutions when washed, by winds and tides, into the margins of marine lagoons, tidal pools and other intertidal regions, from which water was being evaporated.

"This process of enhanced concentrations through evaporation is thought to be important by many researchers since, quite frequently, the presence of water seems to inhibit the process of polymerization or chaining of, say, molecules. Sidney Fox, along with other scientists, has found, for example, that in order to bring about the polymerization of amino acids, the conditions within the experimental apparatus should be anhydrous, that is, done in the absence of water."

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