Thinking to Believe

It’s been a month, but I haven’t forgotten!  For new readers, this is part 6 in my series of posts summarizing Stephen Meyer’s argument for design from his new book, Signature in the Cell.  Past posts can be found here: Parts 1, 2, 3, 4, and 5.

In the last two installments we demonstrated that the OOL cannot be explained by either chance or necessity.  Now we’ll turn our attention to the possibility that the OOL can be explained by a combination of both chance and necessity.  While many models could be examined—and were examined by Meyer—I will only examine the RNA-first, a.k.a. the RNA World hypothesis, since this is the prevailing OOL model today.

The cell presents OOL researchers with a chicken-and-the-egg paradox of which came first: the DNA that makes proteins, or the proteins necessary for replicating DNA?  The paradox was insoluble, so another solution was required.  If neither DNA nor proteins could arise first, what did?

Carl Woese, Francis Crick, and Leslie Orgel proposed an RNA-first model in the late 1960s, followed by Walter Gilbert (Harvard biophysicists) who developed it in the 1980s and gave it its common name.[1]  This model proposes that the first cell consisted of a much simpler self-replicating, self-catalyzing RNA (RNA is similar to DNA, but it is a single strand rather than a double helix, and the nucleotide, thymine, is replaced by uracil).[2]  This model was largely fueled by the discovery of Thomas Cech and Sidney Altman in the early 1980s that sometimes RNA can catalyze chemical reactions like an enzyme does, and thus RNA could serve the dual purpose of information storage (like DNA) and enzymatic functions (like proteins).  “The paradox of the chicken and the egg was thus resolved by the hypothesis that the chicken was the egg.”[3]

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As a result of the failure of the chance hypothesis to explain the origin of life, Dean Kenyon and Gary Steinman proposed a novel solution: life’s origin is due to physical necessity, not chance (Biochemical Predestination, 1969).  Like many others in their day, Kenyon and Steinman were proponents of the protein-first model, maintaining that the first life was based on proteins rather than DNA (DNA came later).  They got around the utterly implausible odds of forming proteins by chance by just denying that chance was involved at all.  They suggested that law-like processes direct the self-organization of chemicals, making the origin of life inevitable, not some lucky happenstance.  Just like electrostatic forces draw sodium and chloride together in ordered patterns to form crystals, some (yet-to-be-discovered) natural law organized biochemicals to form the biological information that makes life possible. 

As evidence for their view that proteins could self-organize to form the basis of life, they pointed to the fact that amino acids bond with certain other amino acids better than others, making certain sequences more likely than others.  This explained how the biological information necessary for life could arise without DNA, RNA, and the transcription-translation process.[1]

Eventually, however, Kenyon came to question his model.  He recognized that even if it could explain the origin of biological information, he still needed to explain the origin of DNA as well as how protein synthesis transformed itself from a self-organizing and self-originating process to one that depended entirely on DNA transcription and translation.  He dismissed the possibility that proteins constructed DNA because the information flow in modern cells is unidirectional, and it’s in the complete opposite direction: information flows from DNA to proteins, not vice-versa.  Because DNA wholly determines the amino acid sequencing of proteins, and because there is no evidence suggesting or reason to think this order was ever different in the past he eventually abandoned the protein-first model.  DNA must have come first.  But based on his knowledge of its chemical properties, he doubted that DNA possessed the same sort of self-organizational properties he thought were present in amino acids.  He was forced by the evidence to abandon his proposal that life originated by necessity.

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Now that we have established what needs explaining (biological information, and the origin and functional interrelatedness of cellular machinery) and the scientific method biologists employ to formulate an explanation, we turn our attention to the four possible explanations for life’s origin: (1) Chance; (2) Necessity; (3) Combination of chance and necessity; (4) Intelligent agency.  In this post I will examine the possibility that life can be explained in terms of chance processes alone.

Just like the lottery, specific probabilities can be assessed for the origin of life by chance.  To illustrate how probabilities are assessed, consider a combination lock.  What are the chances of someone guessing the correct combination of a lock with four dials containing 10 digits each?  To determine the chances one must multiply the number of digits on each dial (10) by itself four times (because there are four dials): 10 x 10 x 10 x 10 = 10,000 different possible combinations.  The chances of guessing the correct combination, then, are 1 in 10,000.  If one more dial was added to the lock, it would decrease the odds by a factor of 10 (1 in 100,000).  If one is given only one try, the odds of getting the right combination are overwhelmingly against him—so much so that if the lock opened everyone would suspect that his selection was not random, but based on intelligence, or that the lock was faulty.  The odds of cracking the combination increase, however, as one increases the number of attempts.  If one is given 100,000 tries to guess the combination, then the odds are that he will eventually guess the combination through random attempts alone (if each try took 10 seconds, you could crack the 4-dial code in about 28 hours, and the 5-dial code in about 11 days).

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What is the scientific method?  Everyone who sat through grade-school science class knows the answer to this question, right?: observation, hypothesis, prediction, experimentation, conclusion.  What may surprise you is that there is no such thing as the scientific method.  There are a variety of methods scientists employ in their quest to discover the truth about the natural world, none of which can be claimed as the scientific method.  Which method a scientist uses depends on what he is studying.  While the method outlined above works well for “experimental scientists” such as chemists and physicists, it doesn’t apply to “historical scientists” (i.e. those who study the past) such as paleontologists, astronomers, and evolutionary biologists.  Those in the historical sciences require a different method.

Historical scientists study the past, not the present.  They seek to discover the historical causes responsible for past events – effects that we observe in the present.  For such a task the scientific method outlined above simply won’t work.  It’s the wrong tool.  To explain the structure of the fossil record, for example, one cannot engage in experimentation.  Likewise, there is no need for making predictions since predictions address the future, not the past.  How, then, do historical scientists test their theories?

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In my first post on Meyer’s Signature in the Cell I discussed information theory, and claimed that the cell exhibits functional information—information that cannot be explained in terms of the physical machinery of the cell.  In this post I want to provide some background on the machinery and inner workings of the cell to provide evidence for the claim that the cell contains complex specified information (functional information), and explain why biologists have come to recognize that DNA stores and transmits “genetic information,” contains a “genetic blueprint” with “assembly instructions,” and expresses a “digital code.” 

The two most basic components of the cell are DNA and proteins.  DNA is made up of a 4 character chemical alphabet: adenine, thymine, guanine, cytosine (these are called nucleotides).  These nucleotides always appear in complimentary pairs: adenine is paired with thymine, and guanine is paired with cytosine. 

Proteins—the workhorses of the cell—are composed of amino acids.  The cell contains 20 different kinds of amino acids.  To create functional proteins, these amino acids must be sequenced together in a specific order, forming a “chain” of amino acids (proteins come in varying lengths, with shorter proteins consisting of ~100 amino acids, most proteins consisting of several hundred, and some as large as 34,350 [titin]).  While there are a number of ways in which amino acids can be sequenced, the vast majority of combinations are functionless.  They sequence must be specified if the protein is to have function (functionality also requires the protein to be folded into a particular shape).

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