Ed Brayton is a journalist, commentator and speaker. He is the co-founder and president of 
I've bashed bad science reporting in the mainstream media, so to be fair I should also praise good science reporting when I see it (and for yet another example of atrocious science reporting, see this post by PZ about one more breathless "this changes everything" story full of nonsense). So today, I come to praise Kenneth Chang, not to bury him, for this New York Times article on a recent paper in Science about reconstructing the precise mutational path that transformed one ancient protein with one function into another protein with a different function. I'll post a long excerpt below the fold that explains the research and its implications well:
In work published last year, Dr. Thornton reported how his group reconstructed an ancestral protein of two hormone receptors found in humans. The two, once identical, diverged along different evolutionary paths. One is now part of the stress response system; the other is involved in different biological processes, including kidney function in many animals.In the new study, the researchers determined the exact positions of more than 2,000 atoms in the ancestral hormone receptor. The receptor existed in animals that lived more than 440 million years ago, before the last common ancestor of people and sharks. Then the researchers examined what occurred during the next 20 million years -- before another split of the evolutionary tree that led to bony fish. "That's the ancestor of you and a salmon," Dr. Thornton said.
In that time, one hormone receptor changed so that it bound most strongly to cortisol, a stress hormone. Bony fish and people have this version, called a glucocorticoid receptor. Sharks do not.
Of the glucocorticoid receptors that have been looked at in different species, five specific mutations are always present and distinguish them from the ancestral receptor. When the scientists introduced the five changes into the ancestral protein, they expected that it would be transformed into a glucocorticoid receptor.
Instead, the protein broke, unable to bind to any hormone.
On further investigation, the scientists found that two other mutations, which had negligible effects by themselves, strengthened some of the protein's folds so it could withstand the other five mutations. The researchers were also able to show several sequences in which the seven mutations could have occurred without the protein's functionality ever deteriorating.
Biologists often point out that evolution does not proceed through random chance. Rather, the process of natural selection -- survival of the fittest -- ruthlessly weeds out mutations detrimental to the survival of a species.
But the findings of Dr. Thornton and his colleagues show that some aspects of evolution do occur solely by chance. The two mutations that reinforced the protein did not directly help the organism. So natural selection did not particularly favor them. It was only by chance that they occurred and persisted to set the groundwork for the other mutations.
For those with access to Science, you can find the full paper here. It's quite an interesting bit of research, the kind of painstaking investigative work that really helps our understanding of evolutionary processes and how they work.
Comments
Good paper, thanks for pointing it out, Ed.
I'm just finishing up "The Blind Watchmaker", and Dawkins is making the point that "random" has a lot of different possible meanings when talking about evolution. Mutations are "random" in the sense that their timing and effects are unpredictable. But once a "random" mutation happens, it must express itself in a pre-existing pool of other genes. It doesn't stand alone, but in context with its environment.
The paper you linked to really illustrates that. It's only because the environment in which the newer mutations occurred was hospitable, due to earlier mutations, that they were able to be effective in helping the organism survive.
I think that's the sense of "random" that most anti-evolutionists fail to understand -- evolution is random mutations, occurring within a pre-existing (i.e. non-random) environment, and that makes a huge difference.
Posted by: Jeff Hebert | August 25, 2007 10:42 AM
Very cool. Thanks for pointing to it Ed.
Posted by: IanR | August 25, 2007 10:49 AM
"-- survival of the fittest --"
Excellent article, but I always cringe when I see or hear that phrase: it's a caricature of natural selection. More accurate (but not as pithy): differential reproductive success of the fittest.
Posted by: dogscratcher | August 25, 2007 11:40 AM
I like to think of evolution not as "survival of the fittest" but as "survival of the good enough."
Posted by: Skemono | August 25, 2007 1:30 PM
Jeff Herbert said:
The sense of "random" that creationists use is that it is not deliberate. IOW, not preplanned. I don't think they fail to understand the sense in which mutations are random to a scientist, they object to the sense in which mutations are not part of some all encompassing plan.
The intractable nature of this whole debate tells me it is not about evidence, or even belief systems. There is an emotional, visceral fear in some people of living in a universe without a Cosmic Babysitter tucking them in at night.
Posted by: BaldApe | August 25, 2007 2:46 PM
This is pure speculation, but I suspect the meaning of "random" for cretinists is, ah, "random". ;-)
That is, it means what they want it to mean at the moment. So, sometimes, perhaps, it has the mathematical meaning; sometimes the common(?) informal (misleading) meaning; sometimes the Big-Woman-in-the-Sky didn't do it meaning (BaldApe's hypothesis); and perhaps other meanings as well? And I wouldn't be too surprised if there were instances of cretinists falling for various mistakes, such as the gambler's fallacy.
Posted by: blf | August 25, 2007 11:09 PM
It seems that this piece has Behe & the Disco Institute in hurricane-force denial-spin mode: http://www.evolutionnews.org/2007/08/there_is_much_handwaving_about.html
Posted by: Hrafn | August 25, 2007 11:27 PM
From the Media Complaints Division post that Hrafn linked to:
"I sought out a biologist working in a research lab"
... who didn't want to give her name for attribution? Is that a good sign? Oh, right, she's probably worried about oppression from the Darwinist Conspiracy.
"the numerous reporters who... [claim]... that ID isn't testable, and then only moments later turn around and say that ID has been proven false by this new research."
More conflating of "proving ID" with "disproving evolution," as if they're the same thing. This research is the gajillionth discovery to contradict IDist claims that evolution can't do the things most scientists say it does. Proving or disproving ID is a separate task, hindered by its lack of any consistent testable hypothesis.
Posted by: MPW | August 26, 2007 1:34 AM
Good points on creationists' use of "random", but that's why I said "Anti-evolutionists" rather than "creationists". I think there is a sizable segment of the population out there who denies evolution because they think it involves complete randomness in the sense that there's no rhyme or reason or constraint on it at all, but who aren't literal 6,000 year-old "God did it magically" creationists.
Absolutely true, though, that even this group is largely basing their reaction on emotion rather than evidence. Good point.
Posted by: Jeff Hebert | August 26, 2007 8:42 AM