Reducible Complexity?

Comments upon reading Iris Fry's The Emergence of Life on Earth Chapters 7 & 8

The discovery of the structure of DNA in 1953 by Watson and Crick (with large contributions from Maurice Wilkins, Rosalyn Franklin, and Linus Pauling, to mention a few) is perhaps the most momentous discovery of the twentieth century. Watson, Crick, and Wilkins got the Nobel, and most of the glory (Franklin was already dead, and Pauling, who came close but missed, already had two of his own) but it is clear that if Watson and Crick had failed, somebody else would have discovered it soon, regardless.

The most important fact that discovery revealed was noted in the very coy finale of the Watson and Crick publication:

“. . . it has not escaped our attention that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material”.

The DNA structure consists of two complementary helices, which upon separation, can produce (with the help of enzymes) two copies of the original. Thus DNA is the long sought autocatalytic molecule that can (help to) reproduce itself. Moreover, it turns out that a specific sequence of the four "bases" in the DNA can code for a unique protein. The mechanism by which this happens, in the words of Richard Dawkins,

... is known, and it is unspeakably wonderful.

The sequence of a segment of DNA is transcribed (by enzymes) into so called messenger RNA (mRNA), exported to ribosomes consisting of another kind of(ribosomal, or rRNA) and proteins, to which come still a third type of RNA (transfer, or tRNA), each one bearing a characteristic amino acid. When the triple of bases in the combining site of the ribosome matches one of the tRNA molecules complementary sequence, it snaps it's amino acid unto the growing protein and goes to find another amino acid of its specific persuasion.

This is a system with a whole lot of moving parts, and every cell has them all. This very complex machinery is a seeming irreducible component of every living system.

Complexity is very attractive to scientists. What they like to do is to find a simple explanation for apparent complexity. So far, this complexity has proven irreducible. If seeming irreducible complexity excites scientists, creationists are even more entranced. How are complex machines produced, they say - by intelligent design (ID). So is this magic really necessary. I have said elsewhere that the origin of life is the last (barely) defensible bastion for ID.

Chapter 7 of Fry is mostly about the experiments of Stanley Miller and Sidney W. Fox, which established that a simulated early reducing atmosphere, with suitable addition of energy, could produce key organic molecules of metabolism. Fry, who is in a department of History and Philosophy of science, likes to emphasize the difference between "metabolism firster" like Oparin, Miller and Fox on the one side, and heredity firsters, like Haldane, on the other.

DNA's structure was discovered more or less simultaneously with the Stanley Miller experiments, and so presumeably did not influence them, but they would be central from that time on.

Chapter 8 starts with a brief (too brief if you have never seen this stuff before) discussion of DNA, its replication and translation into proteins. (But not, of course, as brief, or incomprehensible, as the paragraph that I wrote above - she has molecular diagrams). The main subject is the experiments of Sol Spiegelman, Manfred Eigen, and Leslie Orgel.

Spiegelman's experimental subject was a strand of RNA, the genome of a bacteriophage that infects E. coli, and its replicase, the enzyme that directs its replication. He found that he could get the bacteriophage to reproduce in a test tube when supplied with appropriate nutrients, whereas it normally reproduces only in the cell. Eigen found that the replicase could produce RNA strands without even a template, and Orgel found limited replication with template but no replicase.