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"Your Honor," stated Mr. Mayfield, "I must object. This question already has been asked of, and answered by, the witness. We are going over the same ground."

"Overruled," Judge Arnsberger proclaimed. "I'm going to allow the question."

Dr. Yardley was silent for about ten seconds or so. When he spoke, he said: "Stochastic models provide a way of setting parameters without presupposing any particular kind of metaphysics or ontology. These models offer an opportunity to explore and analyze what does happen against frameworks of expectation and anticipation based on the general properties and characteristics of natural phenomena.

"To say that some given event - such as the coming together, at some point in time and space, of a variety of amino acids generated through separate pathways and conditions - has a finite, although small, possibility of occurring is doing nothing more than to recognize that real events often are capable of reflecting different aspects of our stochastic models. The perfect bridge hand, or throwing x number of consecutive passes at the gaming tables, or winning a lottery against huge odds, and so on, constitute, as far as our stochastic models are concerned, very rare events, but they do happen.

"In fact, the more runs of any given activity that take place, the greater, in general, will be the likelihood of seeing theoretical possibilities being realized or manifested in actual circumstances which one would not expect, on the basis of one's stochastic model, to occur with any degree of frequency. Although the chemical events taking place during prebiotic times may not have been infinite in number, nevertheless, the number of such reactions over the course of 4 to 8 hundred million years is incredibly high.

"Given such large numbers, one might expect, at some point, that certain kinds of improbable events have a chance of taking place. I don't consider such an improbable event an assumption, however unlikely it may be, since it possible occurrence is rooted in a complex stochastic modeling process which acknowledges these kinds of event to be conceivable and capable of taking place in finite, real time."

"When you say, Dr. Yardley, that something is 'capable of taking place in finite, real time', are you saying," Mr. Tappin asked, "that this something must take place or necessarily will take place, or, are you merely saying the event in question could take place under the right circumstances?"

"I'm saying," the professor indicated, "that such an event could take place under the right circumstances and that such circumstances can be assigned some small, but finite, probability of actually occurring."

"What is the nature of this process of assigning some small but finite probability?" the lawyer asked.

"The nature of the assignment process would be shaped by the character of one's stochastic model," replied the professor. "Different models might assign different kinds of probability to this kind of situation."

"Are any of these assignment procedures based on empirical data?" inquired Mr. Tappin.

"Yes, they could be," the professor stated. "It depends on what one is talking about."

"How about," proposed the lawyer, "the coming-together of twenty left-handed-amino-acid-isomers of the sort which are observed to occur in Earth organisms?"

"Well," began the professor, "one would have to figure out how many different kinds of amino acids could have been synthesized under prebiotic conditions. One, then, might, or might not, multiply that number by two, depending on whether one believed ultraviolet light had been polarized slightly in its passage through the Earth's atmosphere and, as a result, had a tendency to decompose right-handed-amino- acid-isomers.

"One also would have to try to work out frequency distribution tables for the different kinds of amino acids, including the 20 in which you are interested. These frequency distribution tables would depend on such things as production efficiency yields and energy efficiency yields for the various stages of amino acid formation which we discussed earlier in the context of the Strecker synthesis process.

"In addition, these frequency distribution tables would have to reflect, in some way, how many amino acids came from extraterrestrial sources. On the other hand, one would have to factor in losses due to pyrolysis, hydrolysis, photolysis, absorption by various clay materials, and so on.

"When one took all of these factors into consideration, one would be in a position to calculate theoretical values about what proportion of the total set of amino acids in existence at any given time were represented by the 20 left-handed amino acids you mentioned. This would provide some sort of stochastic baseline to apply to the real world and from which one's expectations concerning these possibilities would arise.

"Professor Yardley, has anyone worked all this out?" Mr. Tappin asked.

"Models have been developed that take various combinations of these factors into consideration," Dr. Yardley answered. "However, to the best of my knowledge, no one has taken all of these factors into consideration. We simply don't have computers capable of handling the complex dynamics which result from the interaction of all these variables."

"Would one, therefore, Professor, be incorrect in saying there is no complete model of what went on during the Archean era as far as amino acid formation is concerned?" inquired the lawyer?"

"No, this would not be incorrect," acknowledged the professor. "On the other hand, the very essence of science is a constant process of improving, revising, updating, modifying, and, sometimes, rejecting the models which are being constructed.

"Science doesn't purport to have the final answers," added the professor. "It is a work-in-progress, and, as such, it attempts to do the best it can with the material which is available to it.

"As new material, techniques, ideas, and methods have become available, the evolutionary model has been able to improve upon its past performance. The revisions and modifications which have come through this process of gradual, conceptual evolution have created a more rigorous model, but we continue to seek to improve it."

"Given what you have just said," hypothesized the defense counsel, "would one be fair, Dr. Yardley, if one were to say the following? If one does not wish to call the assignment of a probability concerning the likelihood of a bunch of amino acids coming together in the general vicinity of some volcano an 'assumption', then could one fairly say the stochastic model responsible for assigning probabilities in this case stands in need of considerable revision?"

"I don't have a problem with this way of stating things," the professor indicated.

"Dr. Yardley, in all of our discussions up to this point, concerning the different kinds of experiments which have been conducted in relation to origin-of life issues, is it not the case that the various experiments were run with purified compounds under conditions in which there was no chemical competition going on among different kinds of compounds to determine which compounds would form covalent bonds with which compounds?" Mr. Tappin inquired.

"I would say so, yes," the professor replied.

"Would you agree, then, Dr. Yardley," asked the lawyer, "that one might have difficulty understanding how simple condensation cycles of heating and drying might bring about a very selective synthesis of pure polymers, such as proteins, DNA, and RNA - with the right kinds of bonds, optical activity, and monomer composition - from amongst the highly complex mixture of hydrocarbons which may have been available as reactants in the Archean era world?"

"I would agree there is a challenge here for evolutionary theory," admitted the professor, "because there still are quite a few things we don't, yet, understand. I would not agree this challenge necessarily constitutes an insurmountable barrier to our being able to understand these issues eventually.

"Our knowledge base," pointed out the professor, "is developing exponentially. Furthermore, the interim periods required for our knowledge to double is becoming increasingly shorter.

"Phenomena which were inexplicable a few years ago are now being understood. To acknowledge the existence of a problem or challenge, is to participate in the natural order of things in the world of science."

"Professor, consider the following hypothetical situation," requested Mr. Tappin. "Suppose there were a relatively dilute, Archean era, ocean solution of phosphates, carbohydrates, pyrimidines, purines, fatty acids, amino acids, and various kinds of other simpler hydrocarbons.

"Let us further suppose, Dr. Yardley," added the lawyer, "that some of this seawater solution finds its way, via tides and the wind, to some intertidal zonal, or lava, surface. What is likely to happen, once this dilute solution starts to get heated from the sun and/or volcanic-related activity?"

The professor considered the hypothetical situation briefly and, then, began to speak. "Probably, as evaporation proceeded, then, at some point, sodium chloride crystals would form. Bivalent cations, or positively-charged ions and radicals, would interact with organic anions, or negatively-charged hydrocarbon groups. Finally, there would be a very large number, and variety, of covalent bonds which would join together different functional groups in virtually every conceivable combination."

"Would you expect," the counsel for the defense inquired, "that this mixture of ions and covalent bonds would organize itself thermodynamically into a working protocell?"

"If you are asking me," posited the professor, "whether I would expect something interesting to happen in the single exposed lava surface or intertidal puddle which is being examined hypothetically, then I would have to say no, I would not expect such a mixture to organize itself into a working protocell. However, if you were asking me about my expectations in relation to billions of such exposed surfaces and/or intertidal puddles, then I would have to say, yes, I would begin to feel confident in my expectations that at least one of these prebiotic crucibles would be capable of thermodynamically and kinetically organizing itself into something very interesting as far as the origin-of-life issue is concerned."

"Do we have anything," the lawyer queried, "beside your rising level of felt confidence in such expectations, which is likely to persuade us there is something inevitable or necessary about the possibility that, at some time and at some place, there must be a protocell which must emerge from the prebiotic mists? After all, Professor, if you are relying on billions and billions of exposed lava surfaces and intertidal puddles to give rise to at least one interesting protocell or near-protocell, then the prima facie odds against this sort of event happening is billions and billions to one, wouldn't you say?"

"As I indicated earlier," the professor replied, "the more opportunities there are for experimentation with different combinations of possibility, then the greater is the probability that one of these sets of combinations will possess and exhibit the sort of characteristics and properties in which one is interested as far as origin-of-life issues are concerned."

"Dr. Yardley, you seem to be assuming," the lawyer suggested, "that all of these billions and billions of prebiotic crucibles will necessarily be exploring all conceivable possibilities. However, what guarantee do we have that these mini-laboratories, even if they had existed in the hundreds of billions and trillions, either would have been sufficient, or - even if assumed to have been sufficient in number - actually would have explored all the possible combinations available to the molecules in the dilute solutions which have washed up on various exposed surfaces or into some intertidal puddle?"

"Naturally," responded the professor, "there can be no such guarantee."

"Moreover," Mr. Tappin continued without pausing, "what guarantee do we have that even if, on the basis of thermodynamic theory, a given combination is considered possible, that, therefore, from a kinetic perspective, every such thermodynamically conceivable combination will actually occur."

"Again," said the professor, "there can be no guarantee in such matters."

"Or," the lawyer added, "how do we know there won't be a tendency in such mini-laboratories, due to various thermodynamic or kinetic considerations, to repeat, again and again, some finite, but large, set of prebiotic experiments at the expense of other possibilities, and, in the process, consume a great deal of the resources of materials, space, energy and time which are available?"

"All I can say," remarked the professor, "is that, in general terms, you have raised a number of valid issues that need to be addressed. However, the fact these problems have been raised doesn't preclude the possibility of discovering either answers to your challenges or of finding ways which open up the possibility of side-stepping or circumventing these problems in some way."

"At the present time, Dr. Yardley, does evolutionary biology have any remotely satisfying answer for the problems being raised here - yes or no?" specified the lawyer.

"I would have to say no," answered the professor.

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