15. Recent discoveries prove that even at the
microscopic level, life has a quality of complexity that could not
have come about through evolution.
"Irreducible complexity" is the battle cry of Michael J. Behe of
Lehigh University, author of Darwin's Black Box: The Biochemical
Challenge to Evolution. As a household example of irreducible
complexity, Behe chooses the mousetrap -- a machine that could not
function if any of its pieces were missing and whose pieces have no
value except as parts of the whole. What is true of the mousetrap,
he says, is even truer of the bacterial flagellum, a whiplike
cellular organelle used for propulsion that operates like an
outboard motor. The proteins that make up a flagellum are uncannily
arranged into motor components, a universal joint and other
structures like those that a human engineer might specify. The
possibility that this intricate array could have arisen through
evolutionary modification is virtually nil, Behe argues, and that
bespeaks intelligent design. He makes similar points about the
blood's clotting mechanism and other molecular systems.
Yet evolutionary biologists have answers to these objections.
First, there exist flagellae with forms simpler than the one that
Behe cites, so it is not necessary for all those components to be
present for a flagellum to work. The sophisticated components of
this flagellum all have precedents elsewhere in nature, as
described by Kenneth R. Miller of Brown University and others. In
fact, the entire flagellum assembly is extremely similar to an
organelle that Yersinia pestis, the bubonic plague bacterium, uses
to inject toxins into cells.
The key is that the flagellum's component structures, which Behe
suggests have no value apart from their role in propulsion, can
serve multiple functions that would have helped favor their
evolution. The final evolution of the flagellum might then have
involved only the novel recombination of sophisticated parts that
initially evolved for other purposes. Similarly, the blood-clotting
system seems to involve the modification and elaboration of
proteins that were originally used in digestion, according to
studies by Russell F. Doolittle of the University of California at
San Diego. So some of the complexity that Behe calls proof of
intelligent design is not irreducible at all.
Complexity of a different kind -- "specified complexity" -- is the
cornerstone of the intelligent-design arguments of William A.
Dembski of Baylor University in his books The Design Inference and
No Free Lunch. Essentially his argument is that living things are
complex in a way that undirected, random processes could never
produce. The only logical conclusion, Dembski asserts, in an echo
of Paley 200 years ago, is that some superhuman intelligence
created and shaped life.
Dembski's argument contains several holes. It is wrong to insinuate
that the field of explanations consists only of random processes or
designing intelligences. Researchers into nonlinear systems and
cellular automata at the Santa Fe Institute and elsewhere have
demonstrated that simple, undirected processes can yield
extraordinarily complex patterns. Some of the complexity seen in
organisms may therefore emerge through natural phenomena that we as
yet barely understand. But that is far different from saying that
the complexity could not have arisen naturally.
