Irreducible complexity: Encyclopedia II - Irreducible complexity - Stated examples

Irreducible complexity - Stated examples

Behe and others have suggested a number of biological features that they believe may be irreducibly complex.

Irreducible complexity - Flagella

The flagella of certain bacteria constitute a molecular motor requiring the interaction of about 40 complex protein parts, and the absence of any one of these proteins causes the flagella to fail to function. Behe holds that the flagellum "engine" is irreducibly complex because if we try to reduce its complexity by positing an earlier and simpler stage of its evolutionary development, we get an organism which functions improperly. Mainstream scientists regard this argument as having been largely disproved in the light of fairly recent research. The basal body of the flagella has been found to be similar to the Type III secretion system (TTSS), which many bacteria use to secrete toxins. This example of cooption is regarded as strong evidence against Behe's most developed example of irreducible complexity. However, a genetic study of Yersinia pestis bacteria has shown their TTSS is a degenerated flagellum. The bacteria have lost the ability to completely build the flagellum, though they own the complete set of genes for it.

This topic is discussed in the article on the Evolution of flagella.

Irreducible complexity - Blood clotting cascade

The blood clotting cascade in vertebrates is another complex biological pathway that is given as an example of irreducible complexity. For a detailed discussion see the article "Behe and the Blood Clotting Cascade" by George Acton [10].

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