Response to Darrel Falk’s Review of Signature in the Cell
By Stephen C. Meyer
In 1985, I attended a conference that brought a fascinating problem in origin-of-life biology to my attention—the problem of explaining how the information necessary to produce the first living cell arose. At the time, I was working as a geophysicist doing digital signal processing, a form of information analysis and technology. A year later, I enrolled in graduate school at the University of Cambridge, where I eventually completed a Ph.D. in the philosophy of science after doing interdisciplinary research on the scientific and methodological issues in origin-of-life biology. In the ensuing years, I continued to study the problem of the origin of life and have authored peer-reviewed and peer-edited scientific articles on the topic of biological origins, as well as co-authoring a peer-reviewed biology textbook. Last year, after having researched the subject for more than two decades, I published Signature in the Cell, which provides an extensive evaluation of the principal competing theories of the origin of biological information and the related question of the origin of life. Since its completion, the book has been endorsed by prominent scientists including Philip Skell, a member of the National Academy of Sciences; Scott Turner, an evolutionary biologist at the State University of New York; and Professor Norman Nevin, one of Britain’s leading geneticists.
Nevertheless, in his recent review on the Biologos website, Prof. Darrel Falk characterizes me as merely a well-meaning, but ultimately unqualified, philosopher and religious believer who lacks the scientific expertise to evaluate origin-of-life research and who, in any case, has overlooked the promise of recent pre-biotic simulation experiments. On the basis of two such experiments, Falk suggests I have jumped prematurely to the conclusion that pre-biotic chemistry cannot account for the origin of life. Yet neither of the scientific experiments he cites provides evidence that refutes the argument of my book or solves the central mystery that it addresses. Indeed, both experiments actually reinforce—if inadvertently—the main argument of Signature in the Cell.
The central argument of my book is that intelligent design—the activity of a conscious and rational deliberative agent—best explains the origin of the information necessary to produce the first living cell. I argue this because of two things that we know from our uniform and repeated experience, which following Charles Darwin I take to be the basis of all scientific reasoning about the past. First, intelligent agents have demonstrated the capacity to produce large amounts of functionally specified information (especially in a digital form). Second, no undirected chemical process has demonstrated this power. Hence, intelligent design provides the best—most causally adequate—explanation for the origin of the information necessary to produce the first life from simpler non-living chemicals. In other words, intelligent design is the only explanation that cites a cause known to have the capacity to produce the key effect in question.
Nowhere in his review does Falk refute this claim or provide another explanation for the origin of biological information. In order to do so Falk would need to show that some undirected material cause has demonstrated the power to produce functional biological information apart from the guidance or activity a designing mind. Neither Falk, nor anyone working in origin-of-life biology, has succeeded in doing this. Thus, Falk opts instead to make a mainly personal and procedural argument against my book by dismissing me as unqualified and insisting that it is “premature” to draw any negative conclusions about the adequacy of undirected chemical processes.
To support his claim that I rushed to judgment, Falk first cites a scientific study published last spring after my book was in press. The paper, authored by University of Manchester chemist John Sutherland and two colleagues, does partially address one of the many outstanding difficulties associated the RNA world, the most popular current theory about the origin of the first life.
Starting with a 3-carbon sugar (D-gylceraldehyde), and another molecule called 2-aminooxazole, Sutherland successfully synthesized a 5-carbon sugar in association with a base and a phosphate group. In other words, he produced a ribonucleotide. The scientific press justifiably heralded this as a breakthrough in pre-biotic chemistry because previously chemists had thought (as I noted in my book) that the conditions under which ribose and bases could be synthesized were starkly incompatible with each other.
Nevertheless, Sutherland’s work does not refute the central argument of my book, nor does it support the claim that it is premature to conclude that only intelligent agents have demonstrated the power to produce functionally-specified information. If anything, it illustrates the reverse.
In Chapter 14 of my book I describe and critique the RNA world scenario. There I describe five major problems associated with the theory. Sutherland’s work only partially addresses the first and least severe of these difficulties: the problem of generating the constituent building blocks or monomers in plausible pre-biotic conditions. It does not address the more severe problem of explaining how the bases in nucleic acids (either DNA or RNA) acquired their specific information-rich arrangements. In other words, Sutherland’s experiment helps explain the origin of the “letters” in the genetic text, but not their specific arrangement into functional “words” or “sentences.”
Even so, Sutherland’s work lacks pre-biotic plausibility and does so in three ways that actually underscore my argument.
First, Sutherland chose to begin his reaction with only the right-handed isomer of the 3-carbon sugars he needed to initiate his reaction sequence. Why? Because he knew that otherwise the likely result would have had little biologically-significance. Had Sutherland chosen to use a far more plausible racemic mixture of both right and left-handed sugar isomers, his reaction would have generated undesirable mixtures of stereoisomers—mixtures that would seriously complicate any subsequent biologically-relevant polymerization. Thus, he himself solved the so-called chirality problem in origin-of-life chemistry by intelligently selecting a single enantiomer, i.e., only the right-handed sugars that life itself requires. Yet there is no demonstrated source for such non-racemic mixture of sugars in any plausible pre-biotic environment.
Second, the reaction that Sutherland used to produce ribonucleotides involved numerous separate chemical steps. At each intermediate stage in his multi-step reaction sequence, Sutherland himself intervened to purify the chemical by-products of the previous step by removing undesirable side products. In so doing, he prevented—by his own will, intellect and experimental technique—the occurrence of interfering cross-reactions, the scourge of the pre-biotic chemist.
Third, in order to produce the desired chemical product—ribonucleotides—Sutherland followed a very precise “recipe” or procedure in which he carefully selected the reagents and choreographed the order in which they were introduced into the reaction series, just as he also selected which side products to be removed and when. Such recipes, and the actions of chemists who follow them, represent what the late Hungarian physical chemist Michael Polanyi called “profoundly informative intervention[s].” Information is being added to the chemical system as the result of the deliberative actions—the intelligent design—of the chemist himself.
In sum, not only did Sutherland’s experiment not address the more fundamental problem of getting the nucleotide bases to arrange themselves into functionally-specified sequences, the extent to which it did succeed in producing more life-friendly chemical constituents actually illustrates the indispensable role of intelligence in generating such chemistry.
The second experiment that Falk cites to refute my book illustrates this problem even more acutely. This experiment is reported in a scientific paper by Tracey Lincoln and Gerald Joyce ostensibly establishing the capacity of RNA to self-replicate, thereby rendering plausible one of the key steps in the RNA world hypothesis. Falk incorrectly intimates that I did not discuss this experiment in my book. In fact, I do on page 537.
In any case, it is Falk who draws exactly the wrong conclusion from this paper. The central problem facing origin-of-life researchers is neither the synthesis of pre-biotic building blocks (which Sutherland’s work addresses) or even the synthesis of a self-replicating RNA molecule (the plausibility of which Joyce and Tracey’s work seeks to establish, albeit unsuccessfully: see below). Instead, the fundamental problem is getting the chemical building blocks to arrange themselves into the large information-bearing molecules (whether DNA or RNA). As I show in Signature in the Cell, even the extremely limited capacity for RNA self-replication that has been demonstrated depends critically on the specificity of the arrangement of nucleotide bases—that is, upon pre-existing sequence-specific information.
The Lincoln and Joyce experiment that Falk describes approvingly does not solve this problem, at least not apart from the intelligence of Lincoln and Joyce. In the first place, the “self-replicating” RNA molecules that they construct are not capable of copying a template of genetic information from free-standing chemical subunits as the polymerase machinery does in actual cells. Instead, in Lincoln and Joyce’s experiment, a pre-synthesized specifically sequenced RNA molecule merely catalyzes the formation of a single chemical bond, thus fusing two other pre-synthesized partial RNA chains. In other words, their version of ‘self-replication’ amounts to nothing more than joining two sequence specific pre-made halves together. More significantly, Lincoln and Joyce themselves intelligently arranged the matching base sequences in these RNA chains. They did the work of replication. They generated the functionally-specific information that made even this limited form of replication possible.
The Lincoln and Joyce experiment actually confirms three related claims that I make in Signature in the Cell. First, it demonstrates that even the capacity for modest partial self-replication in RNA itself depends upon sequence specific (i.e., information-rich) base sequences in these molecules. Second, it shows that even the capacity for partial replication of genetic information in RNA molecules results from the activity of chemists, that is, from the intelligence of the “ribozyme engineers” who design and select the features of these (partial) RNA replicators. Third, pre-biotic simulation experiments themselves confirm what we know from ordinary experience, namely, that intelligent design is the only known means by which functionally specified information arises.
For nearly sixty years origin-of-life researchers have attempted to use pre-biotic simulation experiments to find a plausible pathway by which life might have arisen from simpler non-living chemicals, thereby providing support for chemical evolutionary theory. While these experiments have occasionally yielded interesting insights about the conditions under which certain reactions will or won’t produce the various small molecule constituents of larger bio-macromolecules, they have shed no light on how the information in these larger macromolecules (particularly in DNA and RNA) could have arisen. Nor should this be surprising in light of what we have long known about the chemical structure of DNA and RNA. As I show in Signature in the Cell, the chemical structures of DNA and RNA allow them to store information precisely because chemical affinities between their smaller molecular subunits do not determine the specific arrangements of the bases in the DNA and RNA molecules. Instead, the same type of chemical bond (an N-glycosidic bond) forms between the backbone and each one of the four bases, allowing any one of the bases to attach at any site along the backbone, in turn allowing an innumerable variety of different sequences. This chemical indeterminacy is precisely what permits DNA and RNA to function as information carriers. It also dooms attempts to account for the origin of the information—the precise sequencing of the bases—in these molecules as the result of deterministic chemical interactions.
Nevertheless, for Professor Falk, drawing any negative conclusions about the adequacy of purely undirected chemical processes—or worse—making an inference to intelligent design, is inherently premature. Indeed, for him such thinking constitutes giving up on science or making “an argument from ignorance.” But this betrays a misunderstanding of both science and the basis of the design argument that I am making.
Scientific investigations not only tell us what nature does, they also frequently tell us what nature doesn’t do. The conservation laws in thermodynamics, for example, proscribe certain outcomes. The first law tells us that energy is never created or destroyed. The second tells us that the entropy of a closed system will never decrease over time. Moreover, because these laws are based upon our uniform and repeated experience, we have great confidence in them. That is why physicists don’t, for example, still consider research on perpetual motion machines to be worth investigating or funding.
In the same way, we now have a wealth of experience showing that what I call specified or functional information (especially if encoded in digital form) does not arise from purely physical or chemical antecedents. Indeed, the ribozyme engineering and pre-biotic simulation experiments that Professor Falk commends to my attention actually lend additional inductive support to this generalization. On the other hand, we do know of a cause—a type of cause—that has demonstrated the power to produce functionally-specified information. That cause is intelligence or conscious rational deliberation. As the pioneering information theorist Henry Quastler once observed, “the creation of information is habitually associated with conscious activity.” And, of course, he was right. Whenever we find information—whether embedded in a radio signal, carved in a stone monument, written in a book or etched on a magnetic disc—and we trace it back to its source, invariably we come to mind, not merely a material process. Thus, the discovery of functionally specified, digitally encoded information along the spine of DNA, provides compelling positive evidence of the activity of a prior designing intelligence. This conclusion is not based upon what we don’t know. It is based upon what we do know from our uniform experience about the cause and effect structure of the world—specifically, what we know about what does, and does not, have the power to produce large amounts of specified information.