Irreducible complexity: Encyclopedia II - Irreducible complexity - Criticisms of irreducible complexity

Irreducible complexity - Criticisms of irreducible complexity

There has been much scientific opposition to the irreducible complexity, with one science writer calling it a "full-blown intellectual surrender strategy." [11] It may be that irreducible complexity does not actually exist in nature: that the examples given by Behe and others are not in fact irreducibly complex, but can be explained in terms of simpler precursors. Thus they would either be merely very complex, or they would be misunderstood or misrepresented.

The precursors of complex systems, when they are not useful in themselves, may be useful to perform other, unrelated functions. Evolutionary biologists argue that evolution often works in this kind of blind, haphazard manner in which the function of an early form is not necessarily the same as the function of the later form. The mammalian ear (derived from a jawbone) and the panda's thumb (derived from a wrist bone spur) are considered classic examples. A current article in Nature, Vol. 439, pp. 318-321 (Jan 19, 2006) by M. Brazeau and P. Ahlberg demonstrates intermediate states leading toward the development of the ear in a Devonian fish (about 360 million years ago). Furthermore, recent research shows that viruses play a heretofore unexpectedly great role in evolution by mixing and matching genes from various hosts.

Evolution can act to simplify as well as to complicate. This raises the possibility that apparently irreducibly complex biological features may have been achieved with a period of increasing complexity, followed by a period of simplification. By analogy, stone arches are irreducibly complex — if you remove any stone the arch will collapse — yet we build them easily enough, one stone at a time, by building over scaffolding that is removed afterward. Similarly, naturally occurring arches of stone are formed by weathering away bits of stone from a large concretion that has formed previously.

Behe has been accused of using an argument by lack of imagination, or constructing a "God of the gaps." Behe himself acknowledges that simply because scientists cannot currently see how an "irreducibly complex" organism could evolve, it does not prove that there is no possible way for it to have occurred.

Niall Shanks and Karl H. Joplin, both of East Tennessee State University, have shown that systems satisfying Behe's characterization of irreducible biochemical complexity can arise naturally and spontaneously as the result of self-organizing chemical processes [12]. They also assert that what evolved biochemical and molecular systems actually exhibit is redundant complexity — a kind of complexity that is the product of an evolved biochemical process. They argue that Behe overestimates the significance of irreducible complexity because his simple, linear view of biochemical reactions results in his taking snapshots of selective features of biological systems, structures and processes, while ignoring the redundant complexity of the context in which those features are naturally embedded and an over-reliance of overly-simplistic metaphors such as his mousetrap.

There has also been a theory that challenges irreducible complexity called facilitated variation. The theory has been presented by Marc W. Kirschner, a professor and chair of Department of Systems Biology at Harvard Medical School, and John C. Gerhart, a professor in the Graduate School, University of California, Berkeley. In their theory they describe how certain mutation and changes can cause irreducible complexity. Their book has been published in 2005.

Irreducible complexity - Gradual replacement

Arguments for irreducibility often assume that things started out the same way they ended up (as we see them now). However, that may not necessarily be the case.

Regarding Behe's antibody example, we have the "marker" substance and the "killer" substance, that together hunt and kill marked invaders. Behe is saying that by themselves, the marker and the killer are useless, and thus must have been made at the same time. The killer cannot kill what it cannot find and the marker has no ability to kill even if it can find a target.

However, under gradual replacement, a different marker may have started out as an independent hunter AND killer. After a while, a helper killer joined this army because it had some nice specialties. However, this second killer still depended on the first one to find the target. Thus the first killer served as both a marker and a killer, and the second killer is just a killer, relying on the first to hunt.

Perhaps over time it is more efficient to have the 2nd killer specialize in killing and the first specialize in marking, and so the first killer is replaced by a similar substance that is merely a marker (perhaps a better marker than the first dual-purpose one).

Thus, each step is an advantage, yet the final result is a dependent pair that does not resemble the proto-killer. This example can be laid out as:

1. A
2. AK
3. AMK
4. MK

All we see today is "MK". Opponents of irreducible complexity state that Behe erroneously assumes that if the structure ended up MK, then it must have started out as M or K by themselves.

Irreducible complexity - Handicaps and sexual selection

According to critics, another overlooked source of "irreducibly complex" features in a sexually reproducing organism is the Handicap Theory. Sexual selection often favors those who can demonstrate to their mates a surplus of energy by maintaining a feature or behavior that is unnecessary for basic survival — sometimes even a hindrance. Examples include certain horns and antlers, display feathers, skin or hair colors and patterns, bony structure, scents, songs, symmetry, and elaborate ritualistic behavior. It is not unreasonable to imagine a handicapping feature eventually developing a useful purpose in a changing environment or for two or more handicapping features to become useful when combined. Conversely, a useful feature may evolve to become a handicapping feature, but through sexual selection the feature is passed through generations to again become useful in a completely different context. In this new context it may seem impossible to us that it was naturally selected to its purpose.

Imagine that a spontaneous hole formed in a pre-bird lizard's lung and quickly became a demonstration to potental mates that it has "energy to burn" because it was successful despite its handicap. Perhaps it evolved as a mating display because it made a distinctive sound like a frog's mating display. That feature could have been maintained by sexual selection long enough to have evolved into the modern bird lung we see today.

However, this objection accounts for relatively few of the virtually unlimited potential intermediate stages of evolving features.

Irreducible complexity - Falsifiability and experimental evidence

Some critics, such as Jerry Coyne (professor of evolutionary biology at the University of Chicago) and Eugenie Scott (a physical anthropologist and executive director of the National Center for Science Education) have argued that the concept of irreducible complexity, and more generally, the theory of intelligent design is not falsifiable, and therefore, not scientific.

Behe argues that the theory that irreducibly complex systems could not have been evolved can be falsified by an experiment where such systems are evolved. For example, he posits taking bacteria with no flagella and imposing a selective pressure for mobility. If, after a few thousand generations, the bacteria evolved the bacterial flagellum, then Behe believes that this would refute his theory.

Other critics take a different approach, pointing to experimental evidence that they believe falsifies the argument for Intelligent Design from irreducible complexity. For example, Kenneth Miller cites the lab work of Barry Hall on E. coli, which he asserts is evidence that "Behe is wrong."

Irreducible complexity - Behe's own Criticisms

In his "Reply to My Critics"^[13], Behe admitted that there was a "defect" in his view of irreducible complexity because, while it purports to be a challenge to natural selection, it does not actually address "the task facing natural selection". Behe specifically explained that the "current definition puts the focus on removing a part from an already functioning system", but the "difficult task facing Darwinian evolution, however, would not be to remove parts from sophisticated pre-existing systems; it would be to bring together components to make a new system in the first place." In that article, Behe wrote that he hoped to "repair this defect in future work". However, such work has not yet been published.

Irreducible complexity - God and Irreducible Complexity

The most basic philosophical criticism of irreducible complexity is that it defeats its own purpose. Namely, that either God is irreducibly complex and hence requires a further creator-of-God (ad infinitum) to create God, or that God is not irreducibly complex, and can be reduced to naturalistic explanation.

Adapted from the Wikipedia article "Criticisms of irreducible complexity", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki