Intelligent Design

There’s an old joke about the philosopher Rudolf Carnap and his method of doing philosophy. According to the joke, Carnap’s method was to begin any philosophical investigation with the statement “Consider a formal language L.” As the good logical positivist he was, Carnap desired the precision inherent in formal languages. Unfortunately, precision has its price. Formal languages are not natural languages and the problems expressible in formal languages need not connect to actual problems in the real world. With formal languages the question ever remains whether they adequately capture the subject under investigation.

Appropriately modified, the joke about Rudolf Carnap can be retold about Stuart Kauffman and the scientific method he employs in At Home in the Universe. According to the modified joke, Kauffman’s method is to begin any scientific investigation with the statement “Consider an NK Boolean network.” Indeed, throughout At Home in the Universe just about every real-world problem gets translated into a toy-world problem involving NK Boolean networks. As with Carnap’s formal languages, NK Boolean networks have the advantage of complete logical precision. But they also suffer the disadvantage of losing touch with reality. And it is this disadvantage which ultimately proves the undoing of Kauffman’s project.

Review of What is Darwinism? And Other Writings on Science and ReligionCharles Hodge, Edited and with an introduction by Mark A. Knoll & David N. LivingstoneGrand Rapids, MI: Baker Books, 1994. 182 pp. The central administration building at Princeton Theological Seminary is Hodge Hall, named after the most prominent and respected Presbyterian theologian in mid-nineteenth-century America. Charles Hodge taught theology Read More ›

Charles Darwin on Social Darwinism Richard Weikart, “A Recently Discovered Darwin Letter on Social Darwinism,” Isis 86 (1995): 609-611. For many decades, historians have debated whether Darwin was himself a social Darwinist, i.e., someone who believed that human beings were and should be subject to the same competitive forces acting on all other living things. The debate is sharpened by Read More ›

Introduction

One of the earliest published suggestions that RNA-catalyzed RNA replication preceded and gave rise to the first DNA-based living cells was made by Carl Woese in 1967, in his book The Genetic Code¹. Similar suggestions were made by Crick and Orgel², for reasons that are not difficult to grasp. Prior to the discovery of catalytic RNAs, proteins were considered by many to be the only organic molecules in living matter that could function as catalysts. DNA carries the genetic information required for the synthesis of proteins. The replication and transcription of DNA require a complex set of enzymes and other proteins. How then could the first living cells with DNA-based molecular biology have originated by spontaneous chemical processes on the prebiotic Earth? Primordial DNA synthesis would have required the presence of specific enzymes, but how could these enzymes be synthesized without the genetic information in DNA and without RNA for translating that information into the amino acid sequence of the protein enzymes? In other words, proteins are required for DNA synthesis and DNA is required for protein synthesis.

This classic “chicken-and-egg” problem made it immensely difficult to conceive of any plausible prebiotic chemical pathway to the molecular biological system. Certainly no such chemical pathway had been demonstrated experimentally by the early 1960s. So the suggestion that RNA molecules might have formed the first self-replicating chemical systems on the primitive Earth seemed a natural one, given the unique properties of these substances.

They carry genetic information and (unlike DNA) occur primarily as single-stranded molecules that can assume a great variety of tertiary structures, and might therefore be capable of catalysis, in a manner similar to that of proteins. The problem of which came first, DNA or proteins, would then be resolved.

Self-replicating RNA-based systems would have arisen first, and DNA and proteins would have been added later. But in the absence of any direct demonstration of RNA catalysis, this suggestion remained only an interesting possibility.

Zen Biology? Jeffrey Levinton, “Life in the Tangled Lane,” a review of Stuart Kauffman, The Origins of Order, Evolution 49 (1995): 575-577. In this review of Kauffman’s magnum opus, Levinton (Ecology and Evolution, SUNY Stony Brook) is cheerfully skeptical. “Kauffman’s model,” he writes, “is at once pervasive, explaining everything. But equally, it explains why we may never be able to Read More ›