Transcript HOW DID LIFE GET HERE – BY DESIGN OR BY CHANCE?

HOW DID LIFE GET HERE – BY DESIGN OR
BY CHANCE?
The
Flagellum
Motor
© Keiichi Namba, 2002
IRREDUCIBLE COMPLEXITY AND THE BACTERIAL
FLAGELLUM
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.
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.”
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.
The Biochemical Challenge
• In 1996, Mike Behe, a Professor of
Biochemistry, saw that the flagellum
system presented a big problem for
Darwin’s 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.
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:
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.
Assembly of the Flagellum
Where does the evidence lead? Design or Chance?
© Keiichi Namba, 2002