#14 Irreducible Complexity

Michael Behe is one of the best Known intelligent design theorists

In his book, Darwin’s Black Box: the Biochemical Challenge to Evolution first published in 1996 (I cite the latest edition of 2006) Behe challenges step-by-step evolution.  Michael Behe rejects NeoDarwinist theories concerning the origin of life through Natural Selection.  He is a Roman Catholic and he believes that God designed and created the first cell.

Behe writes that the advances of science since the 1950s show with piercing clarity that life is based on molecular machines. 

“Molecular machines haul cargo from one place in the cell to another along “highways” made of other molecules, while still others act as cables, ropes, and pulleys to hold the cell in shape.  Machines turn cellular switches on and off, sometimes killing the cell or causing it to grow.  Solar-powered machines capture the energy of photons and store it in chemicals.  Electrical machines allow current to flow through nerves.  Manufacturing machines build other molecular machines, as well as themselves.  Cells swim using machines, copy themselves with machinery, ingest food with machinery.  In short, highly sophisticated molecular machines control every cellular process.  Thus the details of life are finely calibrated, and the machinery of life enormously complex.” (Behe 2006, pages 4-5).

Behe contends that Natural Selection working on variation cannot explain the origin of the systems revealed by biochemistry.  The molecular level is the most fundamental level of life.  Since we have finally reached the ‘bedrock of life’, we are now in a position to make an informed assessment of the mechanism of evolution proposed by Darwin.  Can complex molecular systems be built up by small steps adding components to the system one by one?  The examples of biomolecular systems that Behe (2006) gives include the following:

  • The biochemistry of vision involving rhodopsin.
  • The cilium of eukaryotic cells.
  • The flagellum of bacteria.
  • Blood clotting and fibrinogen.
  • Gated transport of proteins into the lysosome cell organelle for recycling.
  • Antibodies and the immune system.
  • The biosynthesis of the nucleotide AMP (a DNA and RNA subunit).

The theory that these examples illustrate involves the notion of Irreducible Complexity.  A system that is irreducibly complex cannot be formed by numerous, successive, slight modifications.  (William Dembski has introduced the concept of Specified Complexity – see footnote[1]).  Behe writes,

“By irreducibly complex I mean a single system composed of several well-matched, interacting parts that contribute to the basic function, wherein the removal of any one of the parts causes the system to effectively cease functioning.”  (Behe 2006, page 39).

An irreducibly complex system cannot be produced by continuously improving the initial function of a precursor system because any precursor that is missing a part is by definition non-functional.  Behe declares that irreducibly complex biological systems present a powerful challenge to Darwinian evolution since Natural Selection can only choose systems that are already working.  “In order to be a candidate for natural selection a system must have minimal function: the ability to accomplish a task in physically realistic circumstances.” (Behe 2006, page 45).  If a biological system cannot be produced gradually, it would have to arise as an integrated unit for Natural Selection to have anything to act on.

He asks, “How can we recognize an irreducibly complex biological system?”  And answers, “One must specify both the function of the system and all the system components.  An irreducibly complex object will be composed of several parts, all of which contribute to the function”.  This is one example:

“The function of the cilium is to be a motorized paddle.  In order to achieve this function microtubules, nexin linkers, and motor proteins all have to be ordered in a precise fashion.  They have to recognize each other intimately, and interact exactly.  The function is not present if any of the components is missing.  Furthermore, many more factors besides those listed are required to make the system useful for a living cell: the cilium has to be positioned in the right place, oriented correctly, and turned on or off according to the needs of the cell.” (Behe 2006, page 204).

He states that the laws of chemistry work strongly against the undirected development of the biochemical systems that make molecules such as AMP.  The nucleotide AMP which is a component of DNA and RNA is synthesized in 13 steps involving 12 different enzymes (Behe 2006, page 149).  If only the end product is used by the cell while the intermediates are not useful on their own, why would the intermediates evolve one by one?

Behe believes that the universe is the billions of years old that physicists say it is.  He also believes in microevolution, and states that Darwinism explains microevolution very nicely.  Microevolution is defined as the differences between different populations in different geographic areas or ecological niches.  Populations are divisions within a single species.  Behe rejects macroevolution referred to as “large jumps”.  Macroevolution is defined as evolution above the species level.

Behe claims that he finds the idea of common descent –that all organisms share a common ancestor –convincing (Behe 2006, page 5).  This appears to contradict his rejection of ‘macroevolution’.  However, he finally explains his theory of design as follows:

According to Behe, the simplest possible design scenario posits a single cell –formed billions of years ago –that already contained all the information necessary to produce descendant organisms (Behe 2006, page 231).  Thus, four billion years ago, the designer made the first cell, already containing all of the irreducibly complex biochemical systems discussed in the book and many others.  The designs for systems to be used later, such as blood clotting, were present, but not ‘turned on’ in this original cell (Behe 2006, pages 227-228).

My Comment

Behe claims that biochemical ‘machines’ defeat Darwinism and the Theory of Natural Selection.  “Yet for the Darwinian theory of evolution to be true, it has to account for the molecular structure of life.  It is the purpose of this book to show that it does not.” (Behe 2006, page 25).  However, Behe’s opposition to “Darwinian evolution” on the basis that biochemical pathways cannot be built up step by step polarizes positions.

In The Origin of Species Darwin made no claims about biochemical pathways, indeed he made no mention of microscopic cells or unicellular life whose existence was hardly known before the time of Louis Pasteur in the 1860s.  Darwin’s starting point was created multicellular plant and animal archetypes, no doubt complete with biochemical pathways.  Contrary to the statements of Behe, (for example on page 173), Darwin did not claim a natural origin to life via Natural Selection, or address the origin of vision itself.  (The multicellular animals Darwin proposed as archetypes presumably had eyes). 

Behe builds up “Darwinian evolution” far beyond the original claims of Darwin, and then knocks it down.  It is to his contemporary NeoDarwinists that Behe should be addressing himself since it is NeoDarwinian theory that has taken a path directly opposing it to design.  I also oppose NeoDarwinism, but I am a Darwinist since I believe in modification by Natural Selection. 

“Design is simply the purposeful arrangement of parts.” (Behe 2006, page 193).  Design is the ordering of separate components in a system to achieve an identifiable function that is beyond any of the components themselves.  I agree with Behe that many biochemical systems were designed and came into existence as integrated units by the activity of an intelligent Being.  I also agree that “The conclusion of intelligent design flows naturally from the data itself –not from sacred books or sectarian beliefs.”  (Behe 2006, page 193). 

I think, however, that Behe’s idea of common descent involving the creation of one primordial cell that contained the genetic blueprint for all subsequent organisms on Earth in switched-off form is not practicable.  Quite apart from any other considerations, the bacterial cell that would have been the first cell has a genome that does not contain genes.  The single copy DNA of bacteria has operons that are transcribed and translated in a much simpler way to the genes of multicellular organisms.  I conclude that Behe provides no sensible framework in which to hang the details he has so painstakingly described.

[1] Specified Complexity is a mathematical concept belonging to Information Theory.  Irreducible Complexity is a special case of Specified Complexity.  Complex specified information is viewed by Dembski as an empirical marker of purpose, intelligence or design.  This is presented as a mode of scientific explanation since naturalistic explanations are incomplete.  In the Theory of Intelligent Design, an intelligence originated the complexity and specificity found in the cosmos and especially in biological systems.  Dembski writes that “Persons with theological commitments can co-opt this designer and identify this designer with the object of their worship.” (Dembski 2002, page xv).  Dembski (2002, page 318) explains that “specified complexity is not a free lunch in the sense that natural causes cannot generate it.  Nevertheless, natural causes can take already existing specified complexity and shift it around” 

Dembski, William A.  (2002)  No Free Lunch: Why Specified Complexity Cannot Be Purchased Without Intelligence Rowman & Littlefield Publishers, Inc.

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