Intelligent design advocates assert that natural selection could not create irreducibly complex systems, because the selectable function is present only when all parts are assembled.

Professor Miller projected slides that he said contradicted the core of design theory: that organisms are irreducibly complex.

He wrote a lengthy paper about the evolution of flagella and has challenged intelligent design claims that flagella are irreducibly complex.

"Of course," he added, "our findings show that it is not irreducibly complex."

He said such a system would require at least three pieces and perform some specific function to fit his notion of irreducibly complex.

He posits that evolutionary mechanisms cannot explain the development of such "irreducibly complex" systems.

Intelligent design advocates argue that irreducibly complex systems must have been deliberately engineered by some form of intelligence.

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

Although the world started simply, its computation is irreducibly complex.

Based on this scientific research, Miller opined that bacterial flagellum was irreducibly complex beyond the 35 essential components.