Originally Posted by Grace

Sorry Ralph, but I had to steal this from your site



Problems with the Oparin/Miller Hypothesis

Despite its status as textbook orthodoxy, the Oparin chemical evolutionary theory has in recent years encountered severe, even fatal, criticisms on many fronts. First, geochemists have failed to find evidence of the nitrogen-rich "prebiotic soup" required by Oparin's model. Second, the remains of single-celled organisms in the very oldest rocks testify that, however life emerged, it did so relatively quickly, i.e. fossil evidence suggests that chemical evolution had little time to work before life emerged on the early earth. Third, new geological and geochemical evidence suggests that prebiotic atmospheric conditions were hostile, not friendly, to the production of amino acids and other essential building blocks of life. Fourth, the revolution in the field of molecular biology has revealed so great a complexity and specificity of design in even the "simplest" cells and cellular components as to defy materialistic explanation. Even scientists known for a staunch commitment to materialistic philosophy now concede that materialistic science in no way suffices to explain the origin of life. As Francis Crick has written: "An honest man, armed with all the knowledge available to us now, could only state that in some sense, the origin of life appears at the moment to be almost a miracle, so many are the conditions which would have had to have been satisfied to get it going."
To understand the crisis in chemical evolutionary theory, it will be necessary to explain in more detail the latter two difficulties, namely, the problem of hostile pre-biotic conditions and the problem posed by the complexity of the cell and its components.
When Stanley Miller conducted his experiment simulating the production of amino acids on the early earth, he presupposed that the earth's atmosphere was composed of a mixture of what chemists call reducing gases such as methane (CH4), ammonia (NH3) and hydrogen (H2). He also assumed that the earth's atmosphere contained virtually no free oxygen. Miller derived his assumptions about these conditions from Oparin's 1936 book. In the years following Miller's experiment, however, new geochemical evidence made it clear that the assumptions that Oparin and Miller had made about the early atmosphere could not be justified. Instead, evidence strongly suggested that neutral gases such as carbon dioxide, nitrogen and water vapor, not methane, ammonia and hydrogen, predominated in the early atmosphere. Moreover, a number of geochemical studies showed that significant amounts of free oxygen were also present even before the advent of plant life, probably as the result of volcanic outgassing and the photodissociation of water vapor.
This new information about the probable composition of the early atmosphere has forced a serious re-evaluation of the significance and relevance of Miller-type simulation experiments. As had been well know even before Miller's experiment, amino acids will form readily in an appropriate mixture of reducing gases. In a chemically neutral atmosphere, however, reactions among atmospheric gases will not take place readily and those reactions that do take place will produce extremely low yields of biological building blocks. Further, even a small amount of atmospheric oxygen will quench the production of biologically significant building blocks and cause any biomolecules otherwise present to degrade rapidly.
An analogy may help to illustrate. Making amino acids in a reducing atmosphere is like getting vinegar and baking soda to react. Because the reaction releases stored chemical energy as heat (i.e. it is "exothermic"), it occurs easily. Trying to make biological building blocks in a neutral atmosphere, however, is more like trying to get oil and water (or any two inert chemicals) to react.
Stanley Miller's experiment, and others like his, are only relevant to the origin of life if the reducing conditions he assumed actually existed on the early earth. Since independent geochemical evidence now strongly suggests that chemically hostile conditions prevailed, Miller's experiment cannot be said to "simulate" anything. Miller's work was heralded as a positive test of Oparin's chemical evolutionary scenario precisely because he had selected parameters for his experiment in accord with a then-current understanding of early atmospheric conditions. What made Miller's experiment significant was not the production of amino acids per se, but the production of amino acids from presumably plausible prebiotic conditions. As Miller himself stated, "In this apparatus an attempt was made to duplicate a primitive atmosphere of the earth, and not to obtain the optimum conditions for the formation of amino acids." Now, however, the situation has changed. The only reason to continue assuming the existence of a chemically reducing prebiotic atmosphere is that chemical evolutionary theory seems to require it. As Science magazine's Richard Kerr put it, "No geological or geochemical evidence collected in the last 30 years favors a strongly reducing primitive atmosphere. . .Only the success of the laboratory experiments recommends it."
While laboratory simulation experiments have failed to demonstrate the plausibility of chemical evolution, they may have inadvertently demonstrated the necessity of intelligent agency playing an active role in the design of living systems. Ironically, even successful simulation experiments require the intervention of the experimenters to prevent what are known as "interfering cross reactions" and other chemically destructive processes.
Assume for the moment that the reducing gases used by Stanley Miller do actually simulate the conditions on the early earth. Would his experimental results, then, support chemical evolution? Not necessarily. Miller-type simulation experiments have invariably produced non-biological substances in addition to biological building blocks such as amino acids and nucleic acid bases. Without human intervention, these other substances will react readily with biologically relevant building blocks to form a biologically irrelevant compound, a chemically insoluble sludge. To prevent this from happening and to move the simulation of chemical evolution along a biologically promising trajectory, experimenters have often removed those chemicals that degrade or transform amino acids into non-biologically relevant compounds. They must also artificially manipulate the initial conditions in their experiments. Rather than using both short and long-wavelength ultraviolet light which would be present in any realistic atmosphere, they use only short-wavelength UV. Why? The presence of the long-wavelength UV light quickly degrades amino acids. Thus, investigators have routinely manipulated chemical conditions both before and after performing "simulation" experiments in order to protect their experiments from destructive naturally occurring processes. These manipulations constitute what chemist Michael Polanyi called a "profoundly informative intervention."
They seem to simulate, if they simulate anything, the need for an intelligent agent to overcome the randomizing influences of natural chemical processes, processes that lead inexorably, under realistic conditions, to biochemical dead-ends.