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Tuesday, October 4, 2016

An Unconvincing Attempt to Explain Biology as Chemistry

The book What Is Life? How Chemistry Becomes Biology by chemistry professor Addy Pross is an example of the type of reductionism you get when an expert in a particular topic tries to reduce something incredibly complicated to the much simpler topic that the expert is familiar with. So an economist may write a book claiming that human history is just economics, and a hormone expert may claim that human behavior is just the effect of hormones, and an information technology expert may claim that human consciousness is just data processing. Pross's variation on this type of errant reductionism involves an attempt to argue that life is just chemistry. One of his chapters is entitled “Biology Is Chemistry.”

But how can we explain the explosion of information that occurred when life first originated? Pross attempts to discuss this in a section entitled “Information and Its Chemical Roots.” But his discussion is vacuous. First he says (without justification) that “the biological phenomenon of information generation is nothing other than the chemical phenomenon of establishing and enhancing specific catalytic function.” Then he says, “Just as my writing of this book creates information (hopefully), the process of evolution can also create information.” That hardly makes a natural origin of biological information understandable, since an author's writing a book is a deliberate act by a conscious agent, which is not what would be occurring in any natural scenario of the origin of biological information.

Part of the problem of explaining the origin of life is explaining the origin of the genetic code, the complex system of symbolic representations used by life from the beginning. It's hard to imagine any chemical reactions that would have caused that to originate. What does Pross have to say about the genetic code's origin? Nothing. The genetic code does not appear in the index of his book. And what about cells? Of course, explaining the origin of cells is one of the most troubling aspects of explaining the origin of life. But Pross apparently has nothing much to say about that, for I don't found an entry for “cell” or “cells” in his index. And what about explaining the origin of proteins, another gigantic problem in explaining the origin of life? The only index entry for proteins in the index of Pross's book is an entry marked “protein degradation.” Clearly, someone paying little  attention either to the origin of cells or the origin of the genetic code or the origin of proteins is not someone who can justifiably use the phrase “How Chemistry Becomes Biology” as the subtitle of his book. 

The complex structure of a protein molecule
I do find a passing reference to the origin of cells on page 186 of Pross's book, where he says this:

That's when cells, as discrete biological entities, were born. That transition was a highly significant one – one might consider it as a phase transition.

A phase transition is a physics concept. It is what occur when all the particles in a system start behaving in a different way when a certain condition is reached, such as when all the water particles in a liquid start behaving differently when the water freezes. But a phase transition does not involve an appearance of new information or new functionality, so it is worthless in explaining the origin of the complicated biochemical machinery in cells. The origin of cells was not a phase transition.

On page 164 Pross gives a reductionist definition of life, defining it as: “A self-sustaining kinetically stable dynamic reaction network derived from the replication reaction.” Which is a definition of life that only a chemist would give. Do chemists greet visitors by saying, “Greetings, fellow reaction network”?

After reading Pross's book, I'm reminded of the old story about the blind men who were presented with an elephant. One blind man held on to the leg of the elephant and said the elephant is like a tree. Another blind man held on to the tail of the elephant, and said that the elephant was like a rope. Another blind man held on to the tusk of the elephant, and said the elephant was like a spear. Like a blind man holding the tail of an elephant and concluding that the elephant is just a rope, Pross has got hold one of one part of life – chemistry-- and apparently convinced himself that's all there is to life.

But biology cannot be reduced to chemistry, just as chemistry cannot be reduced to physics. Imagine it is early in the history of the universe, before water formed, and you are some mysterious entity studying the universe. You know all about physics and all about the different elements, but you have never seen water. Could you predict from studying the properties of hydrogen and the properties of oxygen that when these two are combined into a molecule you would have something that would have the properties of being wet and drippy? You certainly could not. Chemistry is something that cannot be reduced to physics.

Similarly, biology cannot be reduced to chemistry. Imagine if you were some pure-energy visitor from some other universe who knew nothing about biological life. Imagine you came to the early earth, and studied all the available elements and chemicals, and all the chemical reactions that were occurring, before life appeared. You would have no basis for predicting that any macroscopic biological life would appear. Biological life is not merely chemistry. If you have a dead corpse, you cannot jolt it with some electricity to restart the chemical reactions, and then have a reanimated human that is alive (contrary to the hopes of Victor Frankenstein).