Intelligent design (ID) is the proposition that some features of life on Earth were created abruptly by an intelligent and powerful being rather than being the result of the undirected natural processes of evolution. The proponents of ID claim that it is a legitimate alternative to evolutionary biology and that it deserves equal time in public schools. ID proponents hold that evolution can account only for small changes within species, not for the diversity of biological species on Earth. Some features of biological organisms are considered to be too complex to have evolved through variation, heredity and natural selection. ID proponents claim that organs such as the human eye or the bacterial flagellum (a tiny propeller that allows bacteria to move around) illustrate a kind of complexity that is simply unexplainable through natural causes (a concept called “irreducible complexity”). They have argued that such complex organs cannot function if a single part is malfunctioning or missing, so they could not have evolved gradually ‒ they must have been created as fully functional wholes.
Claims of irreducible complexity have been shown to be false. Studies in molecular biology have shown that the bacterial flagellum could function without some of its parts - not as a locomotion tool, but as a sort of syringe through which the bacterium injects toxins into its host. These studies have classified the bacterial flagellum as an evolved type III secretory apparatus (McNab 1999, Aizawa 2001).
Molecular genetics has allowed the genomes of plants and animals to be mapped, and the genetic similarities and differences between species to be observed. The evidence for evolutionary biology (and against ID) is overwhelming. The facts clearly demonstrate that all forms of life on Earth form a “tree of life” with three big branches (bacteria, archaea and eucarya) and many splitting sub-branches. ID rejects the branching tree model, holding instead that species have no historical connection to each other (known as the “parallel grass blades” model).
ID postulates the existence of an intelligent designer, not considered part of the natural world, which is responsible for the origin of species on Earth. Since the designer is said to be beyond the realm of the observable, claims about its existence can be neither supported nor undermined by observation or experiment.
Therefore ID does not follow the scientific method of systematic observation and experiment, and fails as a scientific hypothesis.
If, however, the Intelligent Designer is considered part of the natural world, it is a form of life. In this case, ID has created a problem bigger than the one it attempts to solve ‒ life on Earth is explained by assuming the existing of a being far more complex and powerful, with no attempt to account for its origins.
Up until today (November 2010), the ID movement has not published a single peer-reviewed article in a recognized scientific journal. ID is religious in nature, being a modern form of Creationism, which is itself derived from a literal and fundamentalist interpretation of the biblical book of Genesis. However, unlike standard Creationists, the supporters of ID may not necessarily agree with the Young Earth hypothesis.
“The Flagellum Unspun: The Collapse of ‘Irreducible Complexity’” Miller, K. 2004.
“Bacterial Flagella and Type III Secretion Systems” Aizawa, S.-I., 2001.