I was recently prompted to read outside of my methodological naturalist’s bubble and delve into Stephen C Meyer’s argument for intelligent design “Signature in the Cell: DNA and the evidence for Intelligent Design” . As a general principle if you want to argue against the misconceptions people hold it is not always enough to have mere facts at your disposal, it helps also to mine the source of their misunderstanding and the plausible quasi-scientific arguments of the likes of Meyer and Michael Behe are fundamental to those who would argue against naturalist theories of the origin of life.
The first thing to say about Meyer is that he is an extremely well qualified philosopher of science and there is very little in Signature in the Cell insofar as it relates to the actual molecular biology of DNA and its role in protein synthesis that I would argue with. In fact the opening chapters would make quite a good undergraduate primer on the subject. He correctly points out that a modern living cell is an incredibly complex machine of interrelated systems capable of transcribing information from the genetic code held in DNA and translating it into large functionally specific molecules such as proteins. He also, and equally correctly, observes that many of these proteins are necessary for the very processes of translation and transcription that the cell relies on to create them, in particular Ribosomes , the RNA / Protein complex that “stitches” amino acids together to make other proteins.
This interrelatedness and complexity forms one plank of his assertion that naturalistic processes cannot be responsible for the origin of life since even a minimally functional cell could not arise without a DNA code and the code could not be translated without specific decoding machinery. Then for further support he argues that there is no known mechanism by which a specific and information rich system can arise by chance alone. All such other know systems; computer code, written language etcetera have an intelligent source: us.
From these he builds a long and rather repetitive argument using abductive reasoning to draw an inference to the best explanation for the origin of life and specifically the information carried by DNA. He cites a number of statistical reasons why chemical theories of the origin of life are impossible, why chance cannot produce specified information and debunks the RNA world hypothesis as a precursor to a full blown DNA code. By systematically eliminating all possible natural explanations for life he seeks to establish that intelligent design is the only possible alternative. However, many of the assumptions he makes to suggest that a naturalistic origin of life is impossible are in my view flawed.
For example there is no necessity for a “minimally functional cell” to arise in one fell swoop and there is no necessity either for replication and metabolism to arise simultaneously or in the same place. There are credible metabolism first scenarios in which thermodynamically favourable conditions can allow spontaneous simple metabolic cycles to emerge. It has been postulated that alkaline hydrothermal vents would have been one such favourable environment. Meyer also insists there are no fundamental forces of nature driving systems to self-organise and increase in complexity but in the last couple of years Jeremy England at MIT has developed a thermodynamic theory that suggests entropy actually favours organised and replicating structures as they are more efficient at energy dispersal. Combinations of replicators and metabolisers allows for the possibility of some kind of biological bootstrapping.
Meyer makes something of a schoolboy error when he argues that the active sites that confer the catalytic specificity to enzymes are so specific that a single amino acid out of place would render them useless. This is something like the classic anti evolution argument of “what use is half an eye?” The answer of course is more use than none as long as it performs the function to some extent. This is true of enzymes as long as they are more efficient at facilitating a particular chemical reaction than would be the case if they were absent, then natural selection will do the rest. In fact it is not even correct to say that enzymes are so constrained. In his book “The arrival of the Fittest” evolutionary biologist Andreas Wagner concludes that no enzyme is really that special, in fact there are usually an astronomical number of alternatives that work and, interestingly, functional intermediates that allow for enzymes to mutate. He also demonstrates similar functional redundancies in the genetic code itself which added together make the probability of specific information bearing molecules arising randomly much greater than Meyer would have us believe.
It gets worse for Meyer when you consider that as things stand we only have one working model for how life is organised, life on earth. For all we know there could be many ways, with alternative molecules and alternative codes for complex evolving systems to arise. Like a Texas sharpshooter he has drawn a bulls eye around one object out of many and made a miracle out of the fact he’s hit it. Should we ever discover extra-terrestrial life with the same familiar genetic code that would be a real argument against random processes and would bolster the case for intelligent intervention but personally I would bet against it.
A parable that Meyer returns to several times goes like this…
"Imagine a team of researchers who set out to explore a string of remote islands near Antarctica. After many days at sea, they arrive on an icy, windswept shore. Shouldering their packs, the team hikes inland and eventually takes shelter from the bitter cold in a cave. There, by the light of a small campfire built to cook their freeze-dried rations, they notice a curious series of wedgelike markings vaguely reminiscent of Sumerian cuneiform. It occurs to them that perhaps these scratches in the rock constitute some sort of written language, but dating techniques reveal that the markings are more than five hundred thousand years old…"He concludes that in this situation once all of the other possible natural causes for the information rich markings are exhausted the researchers would reasonably conclude that an intelligent agent was responsible even though the marks predate writing by many millennia. He then equates this with the information rich genetic code and having (he believes) eliminated natural explanations arrives at the same conclusion. But, these two situations are not equivalent. For one thing markings in a cave would show evidence of tool use. The form and disposition of the rock would indicate whether it had been chiselled with bone, stone or metal implements for example and the marks would have had a predetermined meaning. DNA however is both the medium and the message; there are no fingerprints on it to suggest what mechanism was employed by an intelligent designer to forge a molecule that is self-replicating, prone to mutations and contains multiple redundancies in translation. It’s as if the researchers came across rock markings with no evidence of how they were made, which highlights one of the philosophical problems with the whole book. Meyers argument to a best explanation is really no explanation at all. There is no attempt to explain how the designer achieved this feat of molecular engineering, nor why it bothered. Meyer is of course a Christian so for him the answers would be theological, although he is at pains to tell us that intelligent design says nothing about the nature of the designer only that there must be one.
If, as many religiously motivated people are, you were predisposed to distrust naturalistic explanations for the origins of life this book would be convincing. It’s plausible, so if you were not scientifically literate or up to speed with the latest research into biological origins it could easily confirm your preconceptions. But approached sceptically there are many holes and logical non-sequiturs hiding in the narrative particularly in the latter sections where Meyer attempts to defend intelligent design as proper science. But it’s not enough to posit a cause that itself has no explanation. It’s a philosophical dead end unless you can define who or what the intelligent designer was or at least identify a line of enquiry that may expose it. Meyer denies it at length but it’s hard to distinguish “signature in the cell from any other god of the gaps argument.
