Judgment Day: Intelligent Design on Trial

PBS Airdate: November 13, 2007
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Chapter 8

ROBERT MUISE (Dramatization): Dr. Behe, what is your profession?

MICHAEL BEHE (Dramatization): I am a professor in the department of biological sciences at Lehigh University in Bethlehem, Pennsylvania.

ROBERT MUISE (Dramatization): And you're a biochemist?

MICHAEL BEHE (Dramatization): That's correct, yes.

ROBERT MUISE (Dramatization): How long have you taught at the college level?

MICHAEL BEHE (Dramatization): For 23 years.

ROBERT MUISE (Dramatization): Sir, what is intelligent design?

MICHAEL BEHE (Dramatization): Intelligent design is a scientific theory that proposes that some aspects of life are best explained as the result of design, and that the strong appearance of design in life is real and not just apparent.

ROBERT MUISE (Dramatization): Is intelligent design based on any religious beliefs or convictions?

MICHAEL BEHE (Dramatization): No, it isn't.

ROBERT MUISE (Dramatization): What is it based on?

MICHAEL BEHE (Dramatization): It is based entirely on observable, empirical, physical evidence from nature, plus logical inferences.

ROBERT MUISE (Dramatization): Now when you use the term design, what do you mean?

MICHAEL BEHE (Dramatization): Well, I discussed this in my book, Darwin's Black Box, and a short description of design is shown in this quotation from Chapter 9: "What is design? Design is simply the purposeful arrangement of parts. When we perceive that parts have been arranged to fulfill a purpose, that's when we infer design."

NARRATOR: Part of the defense strategy would be to show the judge examples of biological systems they claimed were too complex to have evolved by natural selection and therefore must have been the product of a designer.

ROBERT MUISE (Dramatization): Can you give us a biochemical example of design, Dr. Behe?

MICHAEL BEHE (Dramatization): Yes, that's on the next slide. I think the best, well, the most visually striking example of design is something called the bacterial flagellum. Now, this is a figure of a bacterial flagellum taken from a textbook, which is widely used in colleges and universities around the country. The bacterial flagellum is, quite literally, an outboard motor that bacteria use to swim. And in order to accomplish that function, it has a number of parts which are ordered to that effect. Now, this part here, which is labeled the filament, is actually the propeller of the bacterial flagellum. The motor is actually a rotary motor.

Most people who see this and have the function explained to them quickly realize that these parts are ordered for a purpose and, therefore, bespeak design.

NARRATOR: Under the microscope, bacteria powered by flagella seem almost acrobatic. They tumble, corkscrew and pirouette, thanks to that whip-like filament.

Driving this propeller is a tiny motor, part of a complex structure made of about 40 different kinds of proteins.

MATTHEW CHAPMAN: The bacterial flagellum looks like a, sort of a Jules Verne notion of what the future looks like. It has a strange sort of mechanical quality to it, these sort of cogs and waving tails and stuff.

NARRATOR: And according to Behe, if any one of these parts is missing from the system, the motor can't function. Behe calls systems like this "irreducibly complex," a term he coined. And he argues such systems could not have evolved naturally.

STEVE FULLER: The idea is that there are certain aspects of life, perhaps organisms or organs or even cells that, in a sense, could only have come about as a whole. In other words, it was very unlikely they could have come about through just a kind of contingent combination of parts over even millions or billions of years, but, rather, in a sense, has to be created whole cloth, all together, at once, because everything fits together so well that to remove one part, the thing wouldn't function.

ROBERT MUISE (Dramatization): Have other scientists acknowledged these design features of the flagellum?

MICHAEL BEHE (Dramatization): Yes, they have. And if you advance to the next slide...

In 1998, a man named David DeRosier wrote an article in the journal Cell, which is a very prestigious scientific journal, entitled "The Turn of the Screw, The Bacterial Flagellar Motor." David DeRosier is a professor of biology at Brandeis University, in Massachusetts, and has worked on the bacterial flagellar motor for most of his career. In that article, he makes the statement, "More so than other motors, the flagellum resembles a machine designed by a human." So David DeRosier also recognizes that the structure of the flagellum appears designed.

DAVID DEROSIER (Brandeis University): What I wrote was, "This is a machine that looks like it was designed by a human." But that doesn't mean that it was designed, that is the product of intelligent design. Indeed, this, more, has all the earmarks of something that arose by evolution.

NARRATOR: Using an electron microscope, DeRosier produces ghostly pictures like this one, revealing the inner workings of what's been called the world's most efficient motor.

DAVID DEROSIER: This is the drive shaft. This transmits this torque generated by the motor that would then turn the propeller, which would push the bacterial cell through the fluid.

NARRATOR: Michael Behe has argued that the flagellum could not have evolved, since its parts have no function for natural selection to act on until they are fully assembled.

But evidence that refutes Behe's claim of irreducible complexity comes from a tiny syringe that injects poison, found in some of the nastiest of all bacteria.

DAVID DEROSIER: This is a structure found, for example, in Yersinia pestis, the bacterium that causes the Bubonic plague. Look at the similarities. Now, this structure doesn't rotate, but it still has to extend this structure, which is equivalent to the rod, the driveshaft here. It has to extend that, because it needs this little channel. It's like, sort of like a syringe. So the virulence factors that are made inside the cell, which is down here, can be exported, pushed up into this hole and exported out through this long, kind of, needle, perhaps into a cell in your body or mine, and thereby create misery.

NARRATOR: And it turns out the two structures look similar for a reason. The syringe on the right is made of a subset of the very same protein types found in the base of the flagellum on the left, though the syringe is missing proteins found in the motor and, therefore, can't produce rotary motion. It functions perfectly as an apparatus for transmitting disease.

DAVID DEROSIER: So if we think about what it means to be irreducibly complex, the argument is that if you take away even one of these proteins, that the structure cannot function. And yet here is a structure that functions, that is missing several of the proteins, and yet here it is, a working, viable organelle of the bacterium. So indeed, the structure is not, in that sense, irreducibly complex.

NARRATOR: To emphasize DeRosier's point, Miller arrived at court making an unusual fashion statement.

KENNETH R. MILLER: As an example of what irreducible complexity means, advocates of intelligent design like to point to a very common machine: the mousetrap. And the mousetrap is composed of five parts. It has a base plate, the catch, a spring, a little hammer that actually does the dirty work, and a bait holder.

The mousetrap will not work if any one of these five parts are taken away. That's absolutely true. But remember the key notion of irreducible complexity, and that is that this whole machine is completely useless until all the parts are in place. Well, that, that turns out not to be true.

And I'll give you an example. What I have right here is a mousetrap from which I've removed two of the five parts. I still have the base plate, the spring, and the hammer. Now you can't catch any mice with this, so it's not a very good mousetrap. But it turns out that, despite the missing parts, it makes a perfectly good, if somewhat inelegant, tie clip.

And when we look at the favorite examples for irreducible complexity, and the bacterial flagellum is a perfect example, we find the molecular equivalent of my tie clip, which is we see parts of the machine missing—two, three, four, maybe even 20—parts, but still fulfilling a perfectly good purpose that could be favored by evolution. And that's why the irreducible complexity argument falls apart.

Chapter 8

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