"According to the information which is available to me," continued Mr. Tappin, "despite years of experimental efforts by hundreds, if not thousands, of scientists and researchers, no one has been able to find a way to replicate or copy a complementary strand of nucleic acids without the assistance of enzymes. Consequently, would you agree Dr. Yardley, that while scientists can generate, in the absence of proteins, a complementary strand for an original strand of RNA, these same scientists cannot copy the complementary strand without the right kinds of enzyme being present?"

"Although, in general, much of what you have said is true," the professor indicated, "I wouldn't agree with your statement without adding at least one qualifying remark. More specifically, two researchers, by the name of McHale and Usher, have demonstrated that when strands of RNA oligonucleotides, consisting of 10 polymerized units or less, are dried and heated in temperatures which approximate sunlight, these RNA oligonucleotides will line up along a complementary template and form polymers or bonded chains similar to the process of replication which occurs in living cells."

"Correct me if I'm wrong, Dr. Yardley, but I believe," suggested the lawyer, "there are a number of differences between the experiment you are describing and the conditions one is likely to be working with in an Archean era environment. First of all, wouldn't you agree, Professor, the experiment to which you are alluding is presupposing what has not, yet, been able to be satisfactorily demonstrated by evolutionary science - namely, that normal RNA nucleotides would have been synthesized and selected out in pure, concentrated forms from amongst the motley array of possibilities involving pentose sugars, different forms of ribose, optical isomers, alternative phosphate bonding possibilities, lack of pyrimidine bases, as well as a variety of odd purine bases in addition to adenine and guanine?"

"Yes, what you say has merit," the professor responded.

"Isn't it also the case, Dr. Yardley," queried the defense counsel, "that in living cells there is an unwinding protein which is able to help separate the individual strands of the double-helix form of nucleic acids which is being held together by Watson-Crick hydrogen bond pairings. In fact, in your previous discussion of Eschenmoser's laboratory creation, pyranosyl RNA, wasn't one of the attractive features of this molecule the fact it offered a possible way around needing a protein to unwind the double-helix structure of nucleic acids?"

"That's right," said the professor.

"Consequently, isn't the McHale-Usher experiment presupposing," Mr. Tappin asserted, "that there was a means, under Archean era conditions, to unwind the strands which spontaneously tend to form double-helix structures through Watson-Crick pairings in order for there to be a complementary, single-stranded template with which to work?"

"This would seem to be the case," the professor agreed.

"To the best of your knowledge, Dr. Yardley, has any ribozyme - that is, an RNA polymer with catalytic activity - been discovered which has the required unwinding capacity which appears to be presupposed by the McHale-Usher experiment?"

"Not as far as I know," answered the professor.

"Furthermore," the lawyer added, "given that the experiment was successful with short polymers of 10 units or less, one is left wondering why the same kind of experiment has not been successful in the replication of much, much longer polymers of nucleic acid as would be required in fully functioning, living cells. In fact, Professor, isn't it the case that part of the lack of experimental success with respect to being able to polymerize long sequences of RNA molecules is due to the instability of the RNA molecule? In other words, isn't it true that the rate of RNA polymerization must take place fast enough to compete with the rate of random, hydrolytic decomposition of the same RNA molecules, and this is difficult to achieve in the absence of protein enzymes which have the capacity to increase reaction rates by magnitudes of between one million and one billion times?"

"Yes, this may be so," responded the professor, "but, if nothing else, I believe the McHale-Usher experiment is very suggestive and carries a lot of implications for the origin-of-life issue."

"Finally, Dr. Yardley, wouldn't you agree," Mr. Tappin inquired, "that the experiment in question is assuming the following. Even if one, or more, normal RNA oligonucleotides, somehow, found their way into existence under Archean era conditions, the researchers do not seem to be allowing for the possibility of the degradation or decomposition of these molecules through hydrolysis, ultraviolet photolysis or pyrolysis?"

"Quite frankly," replied the professor, "I'm not sure I would agree the researchers should have to take any of these factors into consideration. The experiment was intended to show a possibility rather than be a definitive way of resolving all conceivable problems facing evolutionary theory."

"Fair enough," responded the defense counsel, "but would you agree, in turn, that even if McHale and Usher do not have to take any of these various, nevertheless, if evolutionary theory is to provide a plausible account for the origin-of-life through natural processes, then this theory must be able to resolve the problems which are being raised in relation to the McHale-Usher experiment. After all, just as there are positive implications which follow from the McHale-Usher experiment, are there not also a number of negative or problematic implications which are inherent in that same experiment?"

"I guess I can live with this way of stating things," offered the professor.

"During direct examination testimony, Dr. Yardley, you spoke about a number of different ribozymes or sequences of RNA with catalytic properties. If I remember correctly, these properties involved such activities as the cutting and splicing of specific RNA sequences, as well as assuming some limited characteristics of a polymerase by helping to bring about the formation of the bonds which link together certain kinds of polymer chains. Is this right?" the lawyer asked.

"Yes," affirmed the professor.

Mr. Tappin briefly looked through the material he had been holding in his hands while conducting the cross-examination. After five or ten seconds of searching, he pulled out a sheet of paper and placed it on top of the material in his hands.

Eventually, he said: "Dr. Yardley, in doing research concerning some of the experiments dealing with ribozymes, I came across something about which I'm curious. Perhaps, you can help me out.

"At one stage during the particular study that I have in mind," explained the lawyer, "the researchers were interested in determining whether the catalytic specificity exhibited by a naturally occurring ribozyme could be overcome or altered. More precisely, these researchers wanted to see if the ribozyme could be induced to interact equally effectively with a variety of base sequence combinations rather than just the limited nucleic sequences for which the ribozyme, under normal circumstances, seemed to show an inherent, interactive preference.

"In order to overcome the inherent sequence specificity of the ribozyme, the researchers began exploring the possible effects which a variety of polyamines might have on the ribozyme. Although, undoubtedly, Professor, you know what a polyamine is, for the benefit of the jurors, a polyamine, as the name suggests, is a compound that contains two or more amino groups.

"Now," the defense counsel continued, "the simplest of polyamines, such as putrescine [NH₂(CH₂)₄NH₂] and spermine [NH₂(CH₂)₃NH(CH₂)₄-NH(CH₂)₃NH₂] are far more complex than compounds such as hydrogen cyanide (HCN), methane (CH₄), formaldehyde (CH₂O) or ammonia (NH₃). Yet, there is considerable discussion concerning the extent of the availability of even these latter, simple hydrocarbons during Archean era times.

"There were ten polyamines that were tested during the experiment. Only one of these polyamines, spermadine, which is of moderate complexity relative to other polyamines, was found to be capable of inducing the ribozyme to overcome its inherent base sequence specificity.

"Once again, Professor, as was true in relation to the original origin-of-life experiment of Miller, or any of Fox's protenoid experiments, or Eschenmoser's pyranosyl RNA molecule, and numerous other experiments which supposedly simulate the conditions of the prebiotic Archean era, I question the value of such experiments as far as their implications for origin-of-life issues are concerned. How much spermadine, Dr. Yardley, was there in the Archean era world?"

"The short answer to your question," replied the professor, "is that I don't know. "Although polyamines may be more complex than the simpler compounds from which various origin-of-life scenarios usually begin, the quality of complexity does not, in and of itself, automatically mean that polyamines could not have been synthesized under prebiotic conditions.

"As I indicated previously," pointed out the professor, "just because an experiment which is performed does not necessarily faithfully simulate certain aspects of the conditions of the Archean era, this does not mean such an experiment cannot have implications for what might have gone on during prebiotic times. For example, even if one were to assume that spermadine didn't exist during the Archean era, the fact that, under certain conditions, ribozymes can be induced to broaden their catalytic activity, raises the possibility there may have been other agents which did exist during the Archean era and which may have had an effect on ribozymes similar to the action of spermadine.

"If we didn't know about what spermadine helps make possible, we might not have a reason to go looking any further to determine whether there may have been a more plausible prebiotic method for bringing about the same kind of result that spermadine does. In all likelihood, the experiment to which you refer was not, in any technical sense, intended to serve as a simulation experiment, but, nevertheless, this experiment provides evidence that helps shape theory and future experiments as well as strengthens the overall evolutionary model."

"Would you say, Dr. Yardley, that the spermadine experiment constitutes evidence in support of evolutionary theory?" Mr. Tappin inquired.

"If you are asking me," the professor replied, "whether this experiment constitutes a sort of 'smoking gun' which brings us to the brink of completing an unbroken chain of evidence that overwhelmingly and undeniably demonstrates the truth of an evolutionary explanation for the origin-of-life, then my answer is that the spermadine experiment does not provide the kind of evidence in support of evolutionary theory which you are seeking. If, on the other hand, you are asking me whether the spermadine experiment provides information that helps to shape, color, modulate, and orient evolutionary theory, then my answer is that this experiment does constitute evidence in support of evolutionary theory."

| Part 1 | Part 2 | Next | Part 5 | Part 6 |

| Table of Contents For Evolution On Trial |