However, this idea has several shortcomings. When geochemists analyze the sediments from the early history of the earth, they fail to find evidence of a nitrogen-rich prebiotic soup, of the kind predicted by Oparin. Other researchers have determined that the earth’s early atmosphere was most probably not Oparin’s mixture of water vapor and the reducing gases ammonia (a nitrogen compound), methane, and hydrogen. Instead it was a mixture of water and the neutral gases carbon dioxide and nitrogen (Walker 1977, pp. 210, 246; Kerr 1980). Some free oxygen was also included (Kerr 1980; Dimroth and Kimberley 1976). Today, scientists believe most of the oxygen in the earth’s atmosphere came from photosynthesis in plants, but even before plants arose, oxygen could have been derived from the break up of H20 molecules and from gases released into the atmosphere by volcanoes. Even small amounts of free oxygen would hamper the production of amino acids and other molecules necessary for life. The oxygen would make the required reactions more difficult, and it would also, by oxidation, break down any organic molecules that did form.
Despite these difficulties evolutionists maintain their faith that the ingredients for the bodies of the first living things could have formed spontaneously during the earth’s early history. Let us now consider in a more detailed way some of their speculative ideas about how this may have happened. The ideas fall into three main categories: chance, natural selection, and self-organization.
Chance
Some evolutionists propose that chance operating on the molecular level can account for the origin of proteins, which are formed of long chains of amino acid subunits. But there are some big obstacles to such proposals. Let us consider a simple protein composed of 100 amino acid subunits. For a protein to function properly in an organism, the bonds between the amino acids must be peptide bonds. Amino acids can bond with each other in various ways, with peptide bonds occurring half the time. So the odds of getting 100 amino acids with all peptide bonds are
1 in 1030 (10 followed by 30 zeroes). Also each amino acid molecule has a left handed L-form (from laevus, the Latin word for left) and a right handed D-form (from dexter, the Latin word for right). The two forms are mirror images of each other, like right and left shoes, or right and left gloves. In living things, all the proteins are composed of amino acid subunits of the L form. But L and D forms of amino acids occur equally in nature. To get a chain of 100 L-form amino acids, the odds again are 1 in
1030. This is equivalent to flipping a coin and getting heads one hundred times in a row. Therefore, the odds of getting a 100 amino acid chain with all peptide bonds and all L-form amino acids would be about 1 in 1060, which is practically zero odds in the available time limits.
Even if all the bonds are peptide bonds and all the amino acids are L forms, that is still not enough to give us a functional protein. It is not that any combination of amino acid subunits will give us a protein that will contribute to the function of a cell. The right amino acids must be arranged in quite specific orders (Meyer 1998, p. 126). The odds of the right 100 amino acids arranging themselves in the right order are in themselves quite high—about 1 in 1065 (the number of atoms in our galaxy is about 1065 ). Putting this more picturesquely, biochemist Michael Behe (1994, pp. 68–69) says that getting a sequence of 100 amino acids that functions as a protein is comparable to finding one marked grain of sand in the Sahara desert—three times in a row. If you put in the other factors (peptide binding, L-forms only) then the odds go up to 1 chance in 10125. So chance does not seem to work as an explanation for the chem……ical origin of life.
To avoid this conclusion, some scientists appeal to an infinite number of universes. But they have no proof that even one additional universe exists. Neither can they tell us if stable molecules form in any of these imaginary universes (stable molecules are necessary for the kind of life we observe in this universe). We shall consider this topic in greater detail in a later chapter.
Natural Selection
Some scientists, such as Oparin (1968, pp. 146–147), have proposed that natural selection could help select among amino acid chains to produce functional proteins, thus improving the odds that these proteins could form. In other words, protein formation does not rely on pure chance. But there are two problems with this. First, this prebiotic natural selection must operate on amino acid chains that were produced randomly, and we have already seen that the odds are very heavily against getting even a simple chain of amino acids with all peptide bonds and all L forms. So it would be hard to get even the basic raw materials (amino acid chains) upon which natural selection could operate. Second, natural selection involves some kind of molecular replication system. The odds that any such replication system could form by chance are even more remote than the odds against the chance formation of several kinds of amino acid chains upon which natural selection could act. The replication system itself must be made of combinations of highly specific complex protein molecules. Proposals such as Oparin’s therefore confront a major contradiction. Natural selection is supposed to produce the complex proteins, but natural selection requires a reliable molecular replication system, and all such systems known today are formed from complex and very specifically structured protein molecules. Oparin suggested that perhaps the earliest replication system did not have to be very reliable and that the system could make use of proteins that were not as specifically structured as proteins currently found in organisms. But Meyer (1998, p. 127) points out that “lack of . . . specificity produces ‘error catastrophes’ that efface the accuracy of self-replication and eventually render natural selection impossible.”
Despite these difficulties, Richard Dawkins (1986, pp. 47–49), in his book the Blind Watchmaker, still proposes that chance and natural selection (represented by a simple computer algorithm) can yield biological complexity. To demonstrate that the process is workable, he programmed a computer to generate random combinations of letters and compare them to a target sequence that forms an intelligible grammatically correct sentence. Those combinations of letters that come closest to the meaningful target sequence are preserved, whereas those that depart from the target sequence are rejected. After a certain number of runs, the computer produces the target sequence. Dawkins takes this as proof that random combinations of chemicals could by natural selection gradually produce biologically functional proteins. The reasoning is, however, faulty. First, Dawkins assumes the existence of a complex computer, which we do not find in nature. Second, he assumes the presence of a target sequence. In nature there is no target sequence of amino acids that is specified in advance, and to which random sequences of amino acids can be compared. Third, the trial sequences of letters that are selected by the computer do not themselves have any linguistically functional advantage over other sequences, other than that they are one letter closer to the target sequence. For the analogy between the computer algorithm and real life to hold, each sequence of letters chosen by the computer should itself have some meaning. In real life, an amino acid sequence leading up to a complex protein with a specific function should itself have some function. If it has no function, which can be tested for fitness by natural selection, there is nothing on which natural selection can operate. Meyer (1998, p. 128) says, “In Dawkins’s simulation, not a single functional English word appears until after the tenth iteration. . . . Yet to make distinctions on the basis of function among sequences that have no function whatsoever would seem quite impossible. Such determinations can only be made if considerations of proximity to possible future functions are allowed, but this requires foresight that molecules do not have.” In other words, Dawkins’s result can only be obtained because of the element of intelligent design embedded in the whole experiment.