The Problem with Half an Eye

Darwin once stated, “If it could be demonstrated that any complex organ existed which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down.”¹

If Darwin’s general theory of evolution is a valid explanation of how life can develop wholly apart from outside intelligence, then it must be demonstrated to be operating at the molecular level. But does Darwin’s theory hold up under such scrutiny?

Dr. Michael Behe’s book, Darwin’s Black Box,  in essence says, “OK, Charles, take a look at these!” And goes on to cite a handful of examples of what he calls irreducible complexity.

By irreducible complexity, Behe means a single system of interrelated parts, where the absence or failure of any part causes the entire system to non-perform or abort. In an airplane example, it could be a missing wing, rudder, or a defective integral part of the hydraulic system. In the eye, it could be a defective or missing cornea, retina, pupil, optic nerve, etc. All must work in concert for the eye to see.

So how did each of these separate parts evolve together over eons of time? Could the eye have served any purpose without being complete? We are not merely talking about a half-developed eye, but the eye at all its various stages of development throughout hundreds of millions of years (according to Darwin). Darwin himself stated that his theory (that all life is a product of natural processes alone) stands or falls on its ability to explain how an incomplete organ like the eye can benefit a species.

Behe uses a mousetrap as a nonliving example of irreducible complexity. Five basic parts of the trap must work together in order for it to catch mice:

(1) a flat wooden platform

(2) a spring

(3) a sensitive catch that releases when pressure is applied

(4) a metal bar that connects to the catch and holds the hammer back

(5) the hammer that serves as the instrument of death and cruelty for our harmless mouse.

A mousetrap needs each of these parts to kill mice. Each part works interdependently, and so a partially constructed mousetrap serves no function and is worthless.

Behe’s book focuses on a handful of examples, though he states that any biology book contains dozens of them. One of the examples he cites is the microscopic bacterial flagellum, which the bacterium uses as a miniature whip-like rotary motor to propel itself. The flagellum is a swimming device that works similar to a rotary propeller. It is described by Behe like this:

Just picture an outboard motor on a boat and you get a pretty good picture of how the flagellum functions, only the flagellum is far more incredible. The flagellum’s propeller is long and whip-like, made out of a protein called flagellum. This is attached to a drive shaft by hook protein, which acts as a universal joint, allowing the propeller and drive shaft to rotate freely. Several types of protein act as bushing material (like washer/donut) to allow the drive shaft to penetrate the bacterial wall (like the side of a boat) and attach to a rotary motor. … Not only that but the propeller can stop spinning within a quarter turn and instantly start spinning the other direction at 10,000 rpms.²

The flagellum’s molecular motor requires 20 proteins, all working in synchrony, to function. Like the partially constructed mousetrap, the flagellum would be worthless and perish unless all 20 proteins were fully developed.

Dr. Robert Macnab of Yale University detailed the tiny molecular motor of the E. coli flagellum in a 50 page review, concluding that its development cannot be explained by Darwinian evolution. Labeling Darwin’s explanation an “oversimplification,” Macnab questions how a non-functional “preflagellum” could have evolved part by part with each being indispensable to its completed function.³

Another example Behe cites is what he calls “the intracellular transport system” found within cells. The magnified cell in Darwin’s day looked something like an opaque pancake jellyfish with a fuzzy-looking dark spot in the center called the nucleus. It all looked so simple. Only recently, under powerful magnification, have the mysteries of the cell begun to be unveiled.

Molecular biologist Michael Denton uses a similar metaphor to describe the cell’s complexity:

To grasp the reality of life as it has been revealed by molecular biology, we must magnify a cell a thousand million times until it is twenty kilometers in diameter and resembles a giant airship large enough to cover a great city like London or New York. What we would then see would be an object of unparalleled complexity and adaptive design.

On the surface of the cell we would see millions of openings, like the port holes of a vast space ship, opening and closing to allow a continual stream of materials to flow in and out. If we were to enter one of these openings we would find ourselves in a world of supreme technology and bewildering complexity.4

But, again, it is not simply complexity; it is irreducible complexity. Going back to Behe’s illustration of the mousetrap, everything must be in place for the system to work. Missing just one component, the whole system is worthless. Behe remarks,

The point of irreducible complexity is…that the trap we’re considering right now needs all of its parts to function. The challenge to Darwinian evolution is to get to my trap by means of numerous, successive slight modifications. You can’t do it. Besides, you’re using your intelligence as you try. Remember, the audacious claim of Darwinian evolution is that it can put together complex systems with no intelligence at all.5


This post was excerpted from the article “Was Darwin Right About the Eye?”.

¹Charles Darwin, Origin of Species (New York: Bantam Books, 1999), 158.

²Michael Behe, Darwin’s Black Box (New York: Free Press, 2003), 22.

³Macnab, R. (1978), “Bacterial Mobility and Chemotaxis: The Molecular Biology of a Behavioral System,” CRC Critical Reviews in Biochemistry, vol. 5, issue 4, Dec., 291-341.

4Michael Denton, Evolution: A Theory in Crisis (Chevy Chase, MD, Adler & Adler, 1986), 328.

5Quoted in Lee Strobel, The Case for a Creator (Grand Rapids, MI: Zondervan, 2004), 199.