Flagellum Follies
One of the regular contributors over at the Panda's Thumb has a new article out in Nature Reviews Microbiology on the nature of the flagellum. Flagella, for those who don't know, are little whip-like organelles that (mostly unicellular) organisms use to move themselves around. Turns out they are fairly complex machines, which is why they can be found in just about any work making the case for Intelligent Design. Flagella are so complex, it is claimed, that they could not have evolved through a Darwinian process and therefore must have been designed by an active intelligence.The crux of this argument lies on the particular proteins that compose the flagellum. 75% of those proteins, the argument goes, have no use outside of the flagellum itself. Since they are unique to the structure, a Darwinian process would have to develop each of them individually over time for uses that are no longer valid. The unlikeliness of this leads IDers to conclude flagella could not develope by evolution.
What Pallen and Platzack's article does is eliminate this argument by showing that nearly all of the proteins do in fact have homologues in biological systems outside of the flagellum. While this is a sound defeat for IDers, I think it has more significant than simply removing a common argument. The article is good science - it started with a question no one knew the answer to ("Do proteins in the flagellum have exterior homologues?") and did a lot of work to find out the answer. This kind of work exposes ID for what it is. Unlike the work described above which seeks to gain knowledge, ID actually depends on ignorance for its bread and butter. To label a natural object as 'intelligently designed' immediatley makes it uninteresting for further explanatory investigation. Rather, we can only stand back and marvel at its complexity. The flagellum is the perfect example. Upheld as the shining star of irreducible complexity, none of the ID scientists considered the possibility that the facts of protein uniqueness their argument depended upon might be incorrect. While ID proponents were running around shouting about how no one could possibly figure out the origins of the flagellum, real scientists were actually doing the work to find out.
posted by Lame and Blind @ 3:21 PM
5 comments
5 Comments:
The problem with claiming "design" is that science has absolutely no metric by which to determine this. Natural philosophy does, but science/scientific method does not. ID'ers thinking they can step into the scientific arena and claim "it's design!" is just as bad as when certain evolutionary biologists promote their ideas as proof-positive at the non-existence of god.
Neither properly realizes the limits of science.
Good point, but to be fair to IDers they have done a good bit of work trying to work out metrics for design (based on irreducible complexity and specificity). This was one of the main goals of Dembski's 1999 book 'Intelligent Design.'
The metrics fail (and I don't think one that works is possible), but they are out there.
I have some things to say about this but right now I am in nowhereland. Perhaps this weekend I will return to internet that is not pay by the minute.
So I returned earlier than I thought. This is good work by the flagellum folks, my only reservation is that it meets the ID folks on their own terms, and these terms are straight from a fairytale. Perhaps there is no other way, of course, than to meet people on their own terms.
However, the entire discussion of complexity is based on a logical fallacy and a misunderstanding of biological evolution. I have never understood why this is not brought out more. I used to teach science in a Christian high school, so I have waded through all the ID stuff, included the more theoretical and 'sciency' stuff.
Biological systems develop cooperatively and in modules. The complexity argument assumes that things develop linearly, which is simply not the case. Its not as if a cell sets out to develop a flagellum after all. The essence of evolution is little clusters of discrete biochemical function that can be combined in various ways.
Anyway, I am occasionally concerned with the way the ID charges are met by evolutionary biologists, because they show that evolutionary biologists also do not understand their field sometimes.
There is (1) an unhealthy fixation on linearity and teleology. Chaos maths might be helpful to break this bad habit, also packet theories like that dense Wolfram book; (2) an unhealthy fixation on morphology. All the really interesting and important things in biology are at the biochemical and ultrastructural level: how ribosomes work, for example. Viewed from the level of the fundamental problems in biophysics and cellular biology, the difference between, say, a fruitfly and a human are vanishingly small. Woese's tree of life shows this very well. The flagellum problem is not quite so bad, but the spirit of stamp-collecting still lurks in the background.
Thanks for coming back to post that. This is the drum I'm constantly beating as well (full post soon to come). The one area I give ID lots of credit is in bringing out this false assumption that most evolutionists make (though of course IDers alternative is ridiculous). Biologists complain about the ID plague, but they've brought it on themselves.
The assumption is that organisms change in a gradual step-by-step fashion over time. But as you point out, mutation (which is responsible for evolution) doesn't take place at the level of the organism. It takes place at the cellular and genetic levels. And it is not straightforward that a small mutation at that level will be manifested as a gradual change at the organism level. It may be quite different, namely that a small genetic mutation may cause a very large organism shift or even no shift at all. This is what Wolfram showed in his book and what Chomsky has been saying wrt linguistics for at least 15 years.
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