A few weeks ago I blogged about an important series of papers on the evolution of the glucocorticoid receptor gene [see You Can't Go Home Again]. This is work from the Thornton lab and it shows the effect of accumulating neutral mutations over millions of years. I like the papers because it demonstrates clearly where Michael Behe goes wrong in his latest book The Edge of Evolution.Carl Zimmer liked the papers as well and he wrote about them in a great big blog called The New York Times [see Can Evolution Run in Reverse? A Study Says It’s a One-Way Street]. I hate it when he does that. It makes me look bad.
Not surprisingly, Michael Behe read the papers. Surprisingly, he actually thought they helped his case rather that hurt it [see Nature Publishes Paper on the Edge of Evolution]. I was going to follow up on this since it was the reason I brought the papers to your attention in the first place. Now I'm glad I didn't because Carl Zimmer has done a much better job.
Carl asked Joe Thornton to comment on what Michael Behe said on the DISCO website. Thorton replied with a devastating put down of Behe that Carl has posted on The Loom: The Blind Locksmith Continued: An Update from Joe Thornton.
This is a really important article for a variety of reasons. You must read it if you want to learn about modern concepts in evolution.
Here's an excerpt from Thornton's letter that should induce you to visit the rest of the article.
Thanks for asking for my reaction to Behe’s post on our recent paper in Nature. His interpretation of our work is incorrect. He confuses “contingent” or “unlikely” with “impossible.” He ignores the key role of genetic drift in evolution. And he erroneously concludes that because the probability is low that some specific biological form will evolve, it must be impossible for ANY form to evolve.
Behe contends that our findings support his argument that adaptations requiring more than one mutation cannot evolve by Darwinian processes. The many errors in Behe’s Edge of Evolution — the book in which he makes this argument — have been discussed in numerous publications.
In his posts about our paper, Behe’s first error is to ignore the fact that adaptive combinations of mutations can and do evolve by pathways involving neutral intermediates. Behe says that if it takes more than one mutation to produce even a crude version of the new protein function, then selection cannot drive acquisition of the adaptive combination.
[Photo Credit: Joe Thornton by Jack Liu Photographer]
6 comments :
Behe just doesn't understand modern evolutionary theory. He never has understood it. Yet many think he is a legitimate authority on the subject. It makes me want to just scream.
I wish to point out that neutral intermediates are necessary steps in the evolution of adaptation, thus making drift a necessary component in the evolution of adaptations. Recent studies empirically refute the old mantra that "selection is the only mechanism that explains adaptation" (Larry: You are a mindless "accomodationist" to me on that one. Give drift it's due in the origin of adaptations!!!).
Selection is not the only mechanism, and far more often than not, it cannot on its own explain the origin of an adaptation.
I was going to email a suggestion to you to comment on this article, but happily you beat me to it. What a fine, clear explanation of the role of neutral paths, genetic drift and contingency.
Thank you, Dr. Moran, for linking to Thornton's letter. I've already read Behe's three articles which were grossly distorting the meaning of the work of Thornton's research group.
While it is true that I did not pursue a formal education in Biology, I hold an utmost respect and an enthusiastic interest especially in Cell Biology, evolutionary theory and Genetics. However, even though I am a layman when it comes to details, reading articles discussing scientific papers still allows me to spot distorted perspectives and logical fallacies. Of the most annoying things I've read lately were Behe's three articles.
What is truly sad, though, is that all the debate going on and forth is not likely to put an end to the ID-ers' ever-replicating unscientific claims, which, in turn, is a most perverse cover for a so-called controversy in the science world.
"Consider your own life history as an analogy. We can all look back at the road we have traveled and identify chance events that had profound effects on how our lives turned out. “If the movie I wanted to see that night when I was 25 hadn’t been sold out, I never would have gone to that party at my friend’s house, where I met my future spouse….” Everyone can tell a story like this. The probability of the life we actually lead is extraordinarily small. That obviously doesn’t mean that its historical unfolding was impossible."
Thornton just put into words a concept I've always appreciated but could never explain. That might be the best analogy for how the past 4 billion years of evolution gave us the world we have today. He's amazing.
the nice thing in this study is that it shows how adaptive evolution is constrained by non-adaptive change
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