Michael Behe’s concept of irreducible
complexity raises acute difficulties for Darwinism. Irreducible
complexity is a “package-deal” feature of many biological systems.
Package deals are all-or-nothing deals. You can have the whole
package or you can have none of it, but you can’t pick and choose
pieces of it. In biology, especially at the molecular level, there
exist molecular machines (see last question) that cannot be
simplified without losing the machine’s function. In other words,
take away parts and you can’t recover the machine’s function. One
such
irreducibly complex molecular machine that has become the mascot of
the intelligent design movement is the bacterial flagellum. This is
a tiny motor-driven propeller on the backs of certain bacteria. It
is a marvel of nano-engineering,
spinning at tens of thousands of rpm. Biologist Howard Berg at
Harvard calls it “the most efficient machine in the universe.” It is
irreducibly complex.
How do evolutionary theorists propose
to account for such systems? They have no detailed, testable,
step-by-step proposals for how irreducibly complex systems like this
might have arisen. All evolutionary theorists have been able to do
is note that because systems like the flagellum are irreducibly
complex, they must have arisen via a gradual series of simpler
systems that served functions different from the machine in question
(the functions need to be different because to simplify an
irreducibly complex system is to destroy its function). But merely
appealing to such a gradual series of simpler systems doesn’t tell
us how, or even whether, irreducibly complex systems evolved, much
less by Darwinian or other materialist means. The burden on
evolution’s defenders is to demonstrate that at least one
irreducibly complex molecular machine found in nature really can be
formed by some specific, fully articulated series of gradual steps.
So far, evolutionary theorists have nothing like this. Wishful
speculations is the best they’ve come up with.
