The Biological Case Against Evolution

 The intelligent design (ID) argument against evolution has been crafted by ID advocate Michael Behe.  The argument revolves around the existence of complex molecules found in all living cells.  These biological machines, Behe argues, are too complex to have been produced by evolution and thus must be the products of intelligent design.  Behe is wrong.  Darwinism has no trouble explaining sheer complexity.  Four billion years is an unimaginatively long time for things to get complicated. 

 For the last century and a half, a primary way to argue against evolution has been to point to an exceptionally complex and intricate structure and then to challenge an evolutionist to explain how it evolved.  Examples of such challenges have included everything from the human eye to the chemical defenses of the bombardier beetle.  Behe's examples fit this tradition.  He cites the cilia and flagella that produce cell movement, the cascade of blood-clotting proteins, the systems that target proteins to specific sites within the cell, the production of antibodies by the immune system, and the biosynthetic pathways.  The implication is that some biochemical systems cannot have evolved gradually by slight modifications, because without each one of its crucial (basic) parts, the system is "irreducibly complex" and will not function.  Note that this article relies on an essay by cell biologist Dr. Kenneth R. Miller of Brown University (Miller:  2002). 

 The mere existence of structures and pathways that have not yet been provided a step-by-step Darwinian explanation does not successfully make a case against evolution.  Challenges by critics of evolution have backfired when new scientific work provided exactly the evidence they had demanded.  Behe himself made a similar claim in 1994 when he challenged evolutionists to produce transitional fossils linking the first fossil whales with their supposed land-based ancestors (Behe 1994: 61).  Ironically, by the end of 1994, scientists had discovered three transitional fossils linking the first fossil whales and land-dwelling Eocene mammals. 

Irreducible Complexity

 According to Behe, an "irreducibly complex" system is one that is made up of several interacting parts that contribute to the basic function such that the removal of any one of the parts causes the system to effectively cease functioning (Behe 1996: 39).  Such a system supposedly cannot be produced directly by successive slight modifications to the system.  It would have to arise all at once as an integrated unit.  Behe uses a common mechanical device, the mousetrap, as an example of irreducible complexity.  He claims that, since every part of the mousetrap must be in place before it is functional, partial mousetraps, i.e., ones missing one or two parts, are useless.  Extending the analogy to irreducibly complex biochemical machines, Behe asserts these machines cannot function until all of their parts are assembled.  Thus, natural selection could not produce such machines gradually, one part at a time.  They are non-functional until all of their parts are assembled, and natural selection, which can only select functioning systems, would have nothing to work with.  Behe's arguments mirror the classic argument from design. 

 The argument using the common mousetrap to illustrate irreducible complexity can be dispensed with rather easily.  The claim is that the mousetrap cannot function without all of its original parts.  The parts of a conventional mousetrap are a hammer, a spring, a pin (which passes through the center of the spring), a latch, a bar, a platform, and (usually) staples.  Behe is wrong.  The latch can be removed and the bar wedged under the pin.  While less effective, the mousetrap can still function.  Some critics have shown that the trap can still function even if it is successively reduced to fewer parts until only the spring remains.  The mousetrap fails as an example of irreducible complexity.  Behe also has claimed that the clotting cascade could not be reduced.  But there are lab mice from which biologists have removed several parts of the clotting cascade, and the mice seem quite normal. 

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The Biological Case Against Evolution: Pages (1), 2, 3, 4, 5

 

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