1. HOW DID LIFE GET HERE – BY DESIGN OR BY CHANCE? IRREDUCIBLE COMPLEXITY AND THE BACTERIAL FLAGELLUM The Flagellum Motor © Keiichi Namba, 2002

2. Learning Outcomes You should learn: How explanations of many phenomena can be developed using scientific theories, models and ideas. To … develop an argument and draw a conclusion, using scientific and technical language. How uncertainties in scientific knowledge and scientific ideas change over time and about the role of the scientific community in validating these changes.

3. Is Darwinism True? In the Origin of Species, Darwin wrote: If it could be demonstrated that any complex organ existed which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down.

4. How Bacteria Swim Certain bacteria have tiny propellers called flagella which they use to swim. Flagella look like hairs, but up close they are amazingly complex.

5. The Biochemical Challenge In 1996, Mike Behe, a Professor of Biochemistry, saw that the flagellum system presented a big problem for Darwins theory of evolution. He developed the term irreducible complexity to describe this problem. Since 1996, many other professional scientists have agreed with him – including molecular biologist Scott Minnich.

6. Irreducible Complexity Behe defined an IC System as: …a single system that is necessarily composed of several well-matched, interacting parts that contribute to the basic function, and where removal of any one of the parts causes the system to effectively cease functioning. To provide a simple illustration, Behe pointed to a mousetrap as the product of an intelligent design:

7. Have Parts Been Reused? Parts of the flagellum, used for other functions, may have been re-used to evolve the tiny propeller without intelligent direction. However, there are major problems with this idea: 1. Many parts of this tiny propeller are unique to it alone. 2. Assembly instructions for the flagellum also direct the sequence in which the parts will be built, and exactly how they will be assembled. 3. These instructions are read and processed by a network which is itself irreducibly complex. 4. The need to imagine many new part functions for natural selection to select, stretches the scientific credibility of this idea.

8. Assembly of the Flagellum Where does the evidence lead? Design or Chance? © Keiichi Namba, 2002