Behe's Nail

Irreducible Complexity

Where did the information in the DNA which directs the formation of the proteins come from? To build one protein, you typically need 1,200 to 2,000 letters or bases - which is a lot of information. Evolution cannot produce an irreducibly complex biological machine suddenly, all at once, because it is much too complicated. Nor can it produce it indirectly by numerous, successive, slight modifications of a precursor system, because any precursor system would be missing a part and consequently couldn't function . Natural selection can only choose systems that are already working. (Darwin's Black Box , p.39)

The living cell was a "black box"-something that could be observed to perform various functions while its inner workings were unknown and mysterious to Darwin. 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. Dr. 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" (p. 250). The cell is extremely complex and its workings elaborately integrated.

Dr. Behe uses the example of a mouse trap to demonstrate the concept of irreducible complexity. There are only 5 working parts in the mouse trap however if even one of them is removed it will not work properly and catch mice.

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 etc. 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 are present. The system requires all the components to be added at the same time, in the right configuration, before it works at all. Dr. Behe asserts that the complicated biological workings of a cell exhibit the exact same irreducible complexity that we saw in the mousetrap example. In other words, they are all-or-nothing: either everything is there and it works, or something is missing and it doesn't work.

Life is based on molecular machines. Machines haul cargo from one place to another in the cell, others turn cellular switches on and off, and still others manufacture and build other machines. Cells contain molecular motors, solar energy machines, and storage machines. Behe uses the intra-cellular transport system of a cell as an example of irreducible complexity. The cell is not a simple bag of soup, with everything sloshing around inside. Instead in eukaryotic cells - most organisms except bacteria - have a number of compartments, like rooms in a house. There is the nucleus, where the DNA resides, the mitochondria, which produces energy; Each compartment is sealed off by a membrane, just like a room has walls and a door. . . . Counting everything there are more than twenty different sections in each cell. ( Darwin's Black Box pg. 102- 103)

Most new components are made in the ribosome. Denton describes the ribosome as a collection of fifty large molecules containing more than a million atoms. The ribosome functions like an automated factory that can synthesize any protein from DNA instructions. It is astonishing to think that this remarkable piece of machinery which possesses the ultimate capacity to construct every living thing that has ever existed on Earth, from a giant redwood to the human brain, can construct all its own components in a matter of minutes. . . it is several thousand million million times smaller than the smallest piece of functional machinery ever constructed by man. (Evolution a Theory in Crisis; p.338)

Not only is the ribosome amazing but now you have the challenge of getting these new components into the right room. First, you need molecular trucks with their molecular motors to transport a protein. These trucks follow specific highways. There has to be a system to identify which component goes on which truck. If your protein gets misdirected to the wrong area the system fails. Our irreducible system attaches a signal to each protein - a mini ticket that unites the right protein with the correct truck. An additional system is coded to make sure that the truck and its cargo are sent to the correct destination. As a final step when the truck arrives at its destination there is another series of fail-safe procedures. Before the compartment allows the delivery it checks to verify this is the correct protein before allowing the material to enter. Dr. Behe states that it is impossible for the Theory of Evolution to gradually build the complex biological machines that are a hallmark of life. In fact, he reminds us that Darwin's claim is actually much more audacious - since he states that evolution can put together complex systems with no intelligence at all. (Creator and the Cosmos p.199.) According to the evolutionary theory natural selection has NO goal in mind. The proto-creature is not trying to become a giraffe because it knows that a longer neck will allow it to eat the leaves on the tree tops. Behe states that randomly arriving at the complexity of a cell is impossible to contemplate. Molecular and bodily systems are too perfect and fully integrated. His point is that if even one element of a fully integrated system were missing the system would fail. Behe offers the flagellum as an excellent example of irreducible complexity. Not only must all the parts and proteins necessary to build the flagellum be present but all the individual parts must be assembled in the correct sequence.

Building a molecular machine requires genetic assembly instructions which not only tell the cell how to build the specific protein parts they direct when these parts will be built. The rotary motor is created from the inside out. One mechanism counts the number of components in the ring structure of the stator. Once that is assembled a feedback mechanism stops work on that piece. Then a rod is added, followed by a ring. Then another rod is added. Then comes the U-joint. Once the U-joint grows to a certain size and is bent at the proper angle another feedback mechanism shuts off the work on that part. Then the assembly line fabricates the components of the propeller. Those who believe in Darwinian evolution defend natural selection by proposing co-option as the means that nature used to construct this remarkable motor. Co-option is taking a part that was originally designed to do something else and using it to perform in a different manner. Natural selection worked to build complex structures by taking simpler systems that performed a different function earlier and combined them into more complex machines. Critics of Behe’s example of the rotary motor point to the needle-nosed cellular pump as an example. Dr. Ken Miller notes that many of the protein parts in the flagellar motor are found in a simpler machine that pumps proteins through the cell wall. Specifically there are 10 proteins that are also found in the rotary motor. Miller believes that this shows that protein parts from the rotary motor can perform other functions and that natural selection would preserve them because they served a useful function and then co-opted them into the motor assembly of the rotary motor.

There are several problems with the theory of co-option. First the theory glosses over the complexity of uniting diverse systems into a new functional system. A cell's very survival would depend on a patchwork of jury –rigged proteins. As described earlier each mutation or mistranslation would only garble the message. Which of course would heighten the vulnerability of the cell. As H. Allen Orr has said “You may as well hope that half of your cars transmission will suddenly help out in the airbag department.” ( Explore Evolution p. 121.) Dr. Michael Behe explains the problems of evolution and the power of irreducible complexity.

As a further example of the complexity of cells please view the following You tube presentation.

Kinesins