irreducible complexity

Irreducible Complexity: The Challenge to the Darwinian Evolutionary Explanations of many Biochemical Structures

The theory of intelligent design holds that certain features of the universe and of living things are best explained by an intelligent cause, not an undirected process such as natural selection.

“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.”
–Charles Darwin, Origin of Species

With this statement, Charles Darwin provided a criterion by which his theory of evolution could be falsified. The logic was simple: since evolution is a gradual process in which slight modifications produce advantages for survival, it cannot produce complex structures in a short amount of time. It’s a step-by-step process which may gradually build up and modify complex structures, but it cannot produce them suddenly.

Darwin, meet Michael Behe, biochemical researcher and professor at Lehigh University in Pennsylvania. Michale Behe claims to have shown exactly what Darwin claimed would destroy the theory of evolution, through a concept he calls “irreducible complexity.” In simple terms, this idea applies to any system of interacting parts in which the removal of any one part destroys the function of the entire system. An irreducibly complex system, then, requires each and every component to be in place before it will function.

As a simple example of irreducible complexity, Behe presents the humble mousetrap.

irreducible complexity
Shown above is a modified sketch of Behe’s mousetrap as taken from

It contains five interdependent parts which allow it to catch mice: the wooden platform, the spring, the hammer (the bar which crushes the mouse against the wooden base), the holding bar, and a catch. Each of these components is absolutely essential for the function of the mousetrap. For instance, if you remove the catch, you cannot set the trap and it will never catch mice, no matter how long they may dance over the contraption. Remove the spring, and the hammer will flop uselessly back and forth-certainly not much of a threat to the little rodents. Of course, removal of the holding bar will ensure that the trap never catches anything because there will again be no way to arm the system.

Now, note what this implies: an irreducibly complex system cannot come about in a gradual manner. One cannot begin with a wooden platform and catch a few mice, then add a spring, catching a few more mice than before, etc. No, all the components must be in place before it functions at all. A step-by-step approach to constructing such a system will result in a useless system until all the components have been added. The system requires all the components to be added at the same time, in the right configuration, before it works at all.

How does irreducible complexity apply to biology? Behe notes that early this century, before biologists really understood the cell, they had a very simplistic model of its inner workings. Without the electron microscopes and other advanced techniques that now allow scientists to peer into the inner workings of the cell, it was assumed that the cells was a fairly simple blob of protoplasm. The living cell was a “black box”-something that could be observed to perform various functions while its inner workings were unknown and mysterious. Therefore, it was easy, and justifiable, to assume that the cell was a simple collection of molecules. But not anymore. Technological advances have provided detailed information about the inner workings of the cell.

Michael Denton, in his book Evolution: A Theory in Crisis, states “Although the tiniest bacterial cells are incredibly small, weighing less than 10^-12 grams, each is in effect a veritable micro-miniaturized factory containing thousands of exquisitely designed pieces of intricate molecular machinery, made up altogether of one hundred thousand million atoms, far more complicated than any machine built by man and absolutely without parallel in the non-living world.” In a word, the cell is complicated. Very complicated.

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