2007-09-23

Learning about flagella and ID in a history book

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by Neil Godfrey

(There’s a YouTube video discussing the following in more depth. Also an article here.)

I am loving a history by William Rosen, Justinian’s Flea: Plague, Empire and the Birth of Europe, “eccentric” though one reviewer might label it.

But I took time out to read this book to give myself a relaxing diversion from my usual diet of socio-political, ethical and religious tomes and tracts.

So I was caught off-guard when I came to page 203 and a discussion about Darwinian selection, ID (Intelligent Design), and what’s attached to the Yersinia pestis cell membrane. In case you were wondering “What the . . . is a Yersinia pestis?” this is the Wikipedia’s definition:

Gram-negative facultative anaerobic bipolar-staining bacillus bacterium belonging to the family Enterobacteriaceae.

Now that that has been cleared up 😉 we can continue.

The point is that bacteria can propel themselves along through fluid by means of a fantastic little propeller (flagellum) that has about 40-plus parts and rotates up to 15,000 rpm and that ID proponents like to argue could only have been divinely created whole from the first day of everything for it to exist at all.

William Rosen remarks that ID people make the assumption that what they see this little flagellum being used for today — motor-boat propulsion for a tiny bacteria cell — is all they can imagine it was ever used for. And if it was only ever used for propulsion, and if it could not work for propulsion if it was not “as it is now”, then it had to be “designed” that way from its very beginning.

Rosen writes, however:

The weakness — one is tempted to write “irreducible weakness” – of intelligent design is the assumption that the component parts of the flagellum (of the eye, or wing) have always had only a single purpose, a purpose that can only be fulfilled with a complement of other parts. One can only wonder what ID makes of the Type III secretion system, a sort of multiple launch artillery system found on the outside of the Y. pestis cell membrane, since the same proton pump that drives the flagella in motile bacteria also serves as the delivery system that the bacterium uses to batter down the walls that protect their victims . . . and both pumps have a common ancestor.” (pp. 203-204)

I recall the wing and eye arguments against evolution when I was once a captive of a fundamentalist sect. How I wish now at the time I had the wit to debunk the “perfect wing or no wing” argument by pointing to the humble egg-laying chooks, hens, fowl (or whatever others call them) in my parents’ back yard — those feathered hulks that could scarcely “fly” two feet above the ground to reach their perch. Although maybe if I had had that wit then it would only have been met with something like: “See? God has made chooks so that they cannot fly away but are always going to be hanging around so you can find easily find their eggs to eat!”

Anyway, I must admit I have skimmed probably too speedily the pages on microbiology and their evolution in my new history book. But it is a refreshing read that introduces me to times and places and personalities about which I had only the vaguest notions till now. Maybe it’s reassuring to know that when I’m more ready for consulting references about the evolution and workings of bacteria and their means of travel I have something at hand on one of my bookshelves.

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