by Matthew Cobb
The letters page of the Times Literary Supplement continues the debate over Signature in the Cell, with letters from author Stephen Meyer, defending his thesis, and from Thomas Nagel, who originally reviewed the book (more or less favourably). I’ll leave you to draw your own conclusions. I would simply point out that Meyer’s use of the fact that scientists have been unable to fabricate RNA replicators “capable of copying more than about 10 per cent of their nucleotide base sequences” as some kind of argument against pre-biotic evolution (and therefore in favour of supernatural intervention in the evolution of life) misses out the key point that explains so much of evolution: time. If 10% efficiency is all we’ve managed in a few years in the lab, I reckon that’s pretty damn good, and indicates what could easily happen in the tens of millions of years that evolution has to play with.
Sir, – I’ve been honoured by the recent attention my book Signature in the Cell has received on your Letters page following Thomas Nagel’s selection of it as one of his Books of the Year for 2009 (November 27). Unfortunately, the letters from Stephen Fletcher criticizing Professor Nagel for his choice give no evidence of Dr Fletcher having read the book, or of his comprehending the severity of the central problem facing theories of the origin of life that invoke undirected chemical evolution. In Signature in the Cell, I show that, in the era of modern molecular genetics, explaining the origin of life requires – first and foremost – explaining the origin of the information or digital code present in DNA and RNA. In his letters to the TLS (December 2 and 16, 2009), Stephen Fletcher rebukes Nagel (and by implication my book) for failing to acknowledge that “natural selection is a chemical as well as a biological process”. Fletcher further asserts that this process accounts for the origin of DNA and the genetic information it contains. Not only does my book address this very proposal at length, but it also demonstrates why theories of prebiotic natural selection involving self-replicating RNA catalysts – the version of the idea that Fletcher affirms – fail to account for the origin of the genetic information necessary to produce the first selfreplicating organism.
“Ribozyme engineering” experiments have failed to produce RNA replicators capable of copying more than about 10 per cent of their nucleotide base sequences. (Wendy K. Johnston et al, “RNA-Catalyzed RNA Polymerization”, Science 292 (2001): 1319–25.) Yet, for natural selection to operate in an RNA World (in the strictly chemical rather than biological environment that Fletcher envisions), RNA molecules capable of fully replicating themselves must exist. Everything we know about RNA catalysts, including those with partial selfcopying capacity, shows that the function of these molecules depends on the precise arrangement of their information-carrying constituents (ie, their nucleotide bases). Functional RNA catalysts arise only once RNA bases are specifically arranged into information-rich sequences – that is, function arises after, not before, the information problem has been solved. For this reason, invoking prebiotic natural selection in an RNA World does not solve the problem of the origin of genetic information; it merely presupposes a solution in the form of a hypothetical, information-rich RNA molecule capable of copying itself. As the Nobel laureate Christian de Duve has noted, postulations of prebiotic natural selection typically fail because they “need information which implies they have to presuppose what is to be explained in the first place”.
STEPHEN C. MEYER
Discovery Institute, 208 Columbia Street, Seattle, Washington 98104.
Sir, – Stephen Fletcher is surprised that I would recommend a book (Stephen Meyer’s Signature in the Cell) whose conclusions I disagree with. I’m afraid I do that frequently; but let me explain this case. I believe that neither theism, nor atheism, nor agnosticism is clearly ruled out either by empirical evidence or by a priori argument: all are rationally possible positions. If one is a theist, the question arises, what belief about God’s relation to the natural order is compatible with the scientific evidence? Deism, the view that God is responsible for the existence of the universe and its laws, but that He never intervenes, is one possible answer. Defenders of intelligent design claim that the appearance of life as a result only of chemical processes would require accidents so improbable that an interventionist answer is more likely. I am interested particularly in the negative part of this argument – scepticism about the reducibility of biology to chemistry. Though I do not share the motives of intelligent design’s defenders to identify problems with the reductive programme, the problems seem real. Atheists, too, face the question of what conception of the natural order is compatible with their beliefs.
Fletcher says I have been duped, and his reference to Uri Geller suggests that Meyer’s book is a deliberate hoax – that he has offered evidence and arguments that he knows to be false. Like any layman who reads books on science for the general reader, I have to take the presentation of the data largely on trust, and try to evaluate more speculative arguments as best I can. Meyer’s book seems to me to be written in good faith. If he misrepresents contemporary research on the origin of life, I will be grateful to have it pointed out to me. But the RNA world hypothesis Fletcher offers as a refutation is carefully described by Meyer, who argues that while it might help solve some problems (in virtue of the catalytic properties of RNA), it simply pushes back to a different molecule the basic question of how such an extremely complex replicator came into existence, thus allowing natural selection to begin.
Fletcher’s remarks don’t address this problem. He should really hold his nose and have a look at the book. It also should be properly reviewed, since it can’t be adequately assessed in the Letters column. I recommended it in one paragraph, speaking as a grateful reader, but the book deserves a review from someone with the relevant scientific credentials.
THOMAS NAGEL
29 Washington Square, New York 10011.
