Michael Behe: Irreducible complexity
Irreducible complexity essentially states that there are biological structures that could not have evolved from a simpler state. A cell, for example, is composed of hundreds of complex molecular machines. Without any one of those machines, the cell would not work. So the cell is irreducibly complex: It couldn't have evolved from a simpler state because it couldn't have worked in a simpler state, and natural selection can only choose among traits that are already functioning.
Behe offers the example of a mousetrap, which typically has five parts: a wooden base to support the contraption, a metal hammer to pound the mouse, a spring to power the hammer, a catch to release the spring and a metal bar that holds back the hammer. Without any one of these parts, the device is useless. Therefore, a mouse trap is irreducibly complex.
In biology, Behe sees the bacterial flagellum as an irreducibly complex system.
A flagellum works as a propeller to help some bacteria get around. This "propeller" contains about 30 different proteins that make it work -- some act as a motor, some act as a stator and others act as a bushing to guide the driveshaft through the bacterial membrane. Without almost any one of these 30 proteins, the entire system breaks down [ref].
The scientific community responds to irreducible complexity by stating that while it is true that natural selection can only choose among traits that are already functioning, the traits don't have to be functioning in their current form. They could have been serving other purposes when they were chosen as advantageous for their current function.
In the example of the mouse trap, scientists point out that if you remove the catch and metal bar, you've got a tie clip. If you remove the spring, you've got a nice keychain. They also claim that science has already discovered that a group of the proteins that make up bacterial flagella is used by certain bacteria for an entirely different function: It acts as a sort of "molecular pump" in the bacterial membrane.
Biologist Kenneth Miller states, "The point, which science has long understood, is that bits and pieces of supposedly irreducibly complex machines may have different -- but still useful -- functions ... Evolution produces complex biochemical machines by copying, modifying, and combining proteins previously used for other functions" [ref].
William Dembski: Specified complexity
Specified complexity in a system means it could not have occurred by chance and it is not the result of any natural law that says it must be the way it is. A biological system exhibits specified complexity if it meets three criteria:
- Its makeup is not merely the result of a natural law.
- Its makeup is complex.
- Its makeup reflects an "independently given pattern or specification."
For clarification, Dembski refers us to the example of detecting an extraterrestrial radio signal in the movie "Contact."
The radio astronomers in "Contact" detected design in a radio signal when they discovered its pulses reflected all and only the prime numbers from 2 to 101. It was not the result of necessity -- there is no law that requires radio signals to transmit in that pattern; it was complex -- the series of signals was long and so was unlikely to take that particular form by chance; and the series of signals reflected an objective pattern -- one that was specified in mathematics long before the astronomers received the radio signal. This signal had specified complexity, and Ellie Arroway and crew took this as evidence of intelligent design.
According to Dembski, a biological system is clearly designed if it exhibits specified complexity.
The scientific community sees this argument as inherently flawed. It points out that Dembski sets forth a negative hypothesis: Anything not created by chance or law must be designed. But scientists claim that chance, law and design are not mutually exclusive, and they are not the only possibilities. So the process of elimination cannot be applied. And in any event, they say, science does not accept the process of elimination as proof of anything. The scientific method requires a positive hypotheses -- you cannot prove one thing simply by disproving another.
Another objection to Dembski's method of detecting design is that it appears to necessitate prior knowledge of the specified pattern. If the radio astronomers in "Contact" had no knowledge of the natural laws governing radio signals and did not recognize consecutive prime numbers as a mathematical sequence, they would never have detected a pattern. When dealing with something like DNA, scientists claim, there are no externally recognizable patterns and therefore no way to detect if a pattern occurs by chance or was "independently given." Dembski's process of detecting design presupposes design [ref].
William Dembski: Law of Conservation of Information
The Law of Conservation of Information was created by William Dembski and involves some very detailed and complex mathematical equations. At its most basic, Dembski's law states that nature cannot create new information (as in information contained in DNA); it can only work with the information it already has. Therefore, a more complex species -- one that contains more information -- could not have evolved from a less complex species [ref].
The scientific community believes that Dembski is repackaging the creationist argument that the theory of evolution violates the second law of thermodynamics, which states that there is a tendency in nature for complexity to decrease. It claims that science has understood for a long time that this theory applies "only to closed systems, and biological systems are not closed" [ref].