The Miller-Urey experiment represents one of the research programs spawned by the Oparin-Haldane hypothesis. Even though details of our model for the origin of life have changed, this has not affected the basic scenario of Oparin-Haldane. The first stage in the origin of life was chemical evolution. This involves the formation of organic compounds from inorganic molecules already present in the atmosphere and in the water of the early earth. This spontaneous organization of chemicals was spawned by some external energy source. Lightning (as Oparin and Haldane thought), proton radiation, ultraviolet radiation, and geothermal or impact-generated heat are all possibilities.
Hoyle and his associates knew that the smallest conceivable free-living life form needed at least 2,000 independent functional proteins in order to accomplish cellular metabolism and reproduction. Starting with the hypothetical primordial soup he calculated the probability of the spontaneous generation of just the proteins of a single amoebae. He determined that the probability of such an event is one chance in ten to the 40 thousandth power, i.e., 1 in 1040,000. Prior to this project, Hoyle was a believer in the spontaneous generation of life. This project, however, changed his opinion 180 degrees. Hoyle stated: "The likelihood of the formation of life from inanimate matter is one to a number with 40 thousand naughts [zeros] after it. It is enough to bury Darwin and the whole theory of evolution. There was no primeval soup, neither on this planet nor on any other, and if the beginnings of life were not random they must therefore have been the product of purposeful intelligence." Hoyle also concluded that the probability of the spontaneous generation of a single bacteria, "is about the same as the probability that a tornado sweeping through a junk yard could assemble a 747 from the contents therein."
The understanding of the origin of life was largely speculative until the 1920s, when Oparin and Haldane, working independently, proposed a theoretical model for "chemical evolution." The Oparin-Haldane model suggested that under the strongly reducing conditions theorized to have been present in the atmosphere of the early earth (between 4.0 and 3.5 billion years ago), inorganic molecules would spontaneously form organic molecules (simple sugars and amino acids). In 1953, Stanley Miller, along with his graduate advisor Harold Urey, tested this hypothesis by constructing an apparatus that simulated the Oparin-Haldane "early earth." When a gas mixture based on predictions of the early atmosphere was heated and given an electrical charge, organic compounds were formed (; ). Thus, the Miller-Urey experiment demonstrated how some biological molecules, such as simple amino acids, could have arisen abiotically, that is through non-biological processes, under conditions thought to be similar to those of the early earth. This experiment provided the structure for later research into the origin of life. Despite many revisions and additions, the Oparin-Haldane scenario remains part of the model in use today. The Miller-Urey experiment is simply a part of the experimental program produced by this paradigm.
During the last two decades, the notion of a primordial soup has not fared too well either. Studies of the atmosphere, ultraviolet radiation, and the dilutional effect of a large body of water, have convinced many scientists that the ocean could not have developed into the "hot dilute soup" that was envisioned by Darwin, Oparin, and Haldane.
Despite absolutely no geological evidence for the existence of this "primeval soup" the Oparin-Haldane-Urey theories became scientific dogma. These foundational assumptions have provided the framework for the modern theory of evolution for the last several decades.
Wells says that the Miller-Urey experiment should not be taught because the experiment used an atmospheric composition that is now known to be incorrect. Wells contends that textbooks don't discuss how the early atmosphere was probably different from the atmosphere hypothesized in the original experiment. Wells then claims that the actual atmosphere of the early earth makes the Miller-Urey type of chemical synthesis impossible, and asserts that the experiment does not work when an updated atmosphere is used. Therefore, textbooks should either discuss the experiment as an historically interesting yet flawed exercise or not discuss it at all. Wells concludes by saying that textbooks should replace their discussions of the Miller-Urey experiment with an "extensive discussion" of all the problems facing research into the origin of life.
These allegations might seem serious; however, Wells's knowledge of prebiotic chemistry is seriously flawed. First, Wells's claim that researchers are ignoring the new atmospheric data, and that experiments like the Miller-Urey experiment fail when the atmospheric composition reflects current theories, is simply false. The current literature shows that scientists working on the origin and early evolution of life are well aware of the current theories of the earth's early atmosphere and have found that the revisions have little effect on the results of various experiments in biochemical synthesis. Despite Wells's claims to the contrary, new experiments since the Miller-Urey ones have achieved similar results using various corrected atmospheric compositions (; ; ). Further, although some authors have argued that electrical energy might not have efficiently produced organic molecules in the earth's early atmosphere, other energy sources such as cosmic radiation (e.g., ), high temperature impact events (e.g., ), and even the action of waves on a beach () would have been quite effective.
Oparin envisioned the production of cellular building blocks in the atmosphere as a result of lightning. Once produced, these chemicals would theoretically build up in the primordial oceans and combine to form the first living systems. However, it has been estimated that it would take up to two years for amino acids to fall from the atmosphere into the ocean. This is a huge problem because even small amounts of ultraviolet radiation would destroy the building blocks before they reached the oceans. Furthermore, as we saw earlier, lack of ozone would further expedite this destruction.
There is one other hurdle that must be successfully cleared if the evolutionists scenario on the origin of life is to have credibility. This is the problem of chemical equilibrium. In any broth or solution, there is the tendency for the materials to become evenly distributed with time. This tendency is called the development of equilibrium.
Even if Wells had been correct about the Miller-Urey experiment, he does not explain that our theories about the origin of organic "building blocks" do not depend on that experiment alone (). There are other sources for organic "building blocks," such as meteorites, comets, and hydrothermal vents. All of these alternate sources for organic materials and their synthesis are extensively discussed in the literature about the origin of life, a literature that Wells does not acknowledge. In fact, what is most striking about Wells's extensive reference list is the literature that he has left out. Wells does not mention extraterrestrial sources of organic molecules, which have been widely discussed in the literature since 1961 (see ; ; ). Wells apparently missed the vast body of literature on organic compounds in comets (e.g. ; ; ), carbonaceous meteorites (e.g. ; ; ; ), and conditions conducive to the formation of organic compounds that exist in interstellar dust clouds ().
All of this evidence supports the fact that there was abundant oxygen on the early earth. However, with or without oxygen, evolution is in a no-win situation. Spontaneous generation could not have occurred either with oxygenor without it!