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UNC researchers outline molecular changes, rebutting the creationist view

Discussion in 'Science & Technology' started by Coyote, Sep 15, 2007.

  1. Coyote

    Coyote Active Member

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    Coyote died for your sheep
    The thought that certain things are so complex they couldn't possibly have evolved naturally is one of the cornerstones of "Intellegent Design" (or Creationism in fancy dress). Scientists are now discovering ways in which some of the most basic systems in living creatures may well have evolved. The study of evolution goes far beyond simple morphology and the fossil record.



    Study maps evolution's tiny steps

    UNC researchers outline molecular changes, rebutting the creationist view


    Yonat Shimron, Staff Writer
    For the first time, scientists have drawn a detailed map of the evolutionary steps taken by a protein that links modern humans to a creature that swam in the oceans 450 million years ago.

    The study, published Thursday in the journal Science, provides further rebuttal to creationists by filling in the gaps that show how evolution occurred on a molecular level.

    Researchers at UNC-Chapel Hill and the University of Oregon looked at a precursor to a modern protein called the glucocorticoid receptor. In humans, the protein lives in the adrenal glands and helps regulate the body's stress response.

    Through a complicated computer analysis, researchers were able to re-create the ancient protein as it existed 450 million years ago in a jawed, ocean-dwelling creature that had no bones, only cartilage. From there, they re-created the protein's progression into its modern form in human beings, finding forks in the evolutionary road that could have led to a different destiny.

    Lead author Eric Ortlund, a postdoctoral fellow at UNC-CH and now an assistant professor of biochemistry at Emory University in Atlanta, said the protein went through seven key evolutionary mutations on its way to becoming what it is today.

    Some of those changes caused a functional shift in the protein. Others were what researchers called "permissive" mutations, paving the way for the more significant mutations without changing the protein's function.

    The researchers likened the permissive mutations to reinforcements on a house that are necessary before major renovations can be undertaken. The reinforcements buttress the house, providing support for the renovations that follow, but they do not fundamentally alter the function of the house.

    The discovery of the role these permissive mutations play is especially significant.

    "The most striking finding was that these mutations had no effect on the function of the protein, but if they hadn't occurred, the protein wouldn't have tolerated later mutations," said Joe Thornton, professor of biology at the University of Oregon and one of the study's authors.

    The researchers regard the permissive mutations as chance events, and they suggest that if evolution could be rewound and set into motion again, a very different outcome might have resulted. Although human beings would still likely have evolved, the scientists said, their chemistry might be different.

    "A lot of people consider evolution to be deterministic," said Matt Redinbo, professor of chemistry, biochemistry and biophysics at UNC-CH, referring to the theory that evolution follows one particular path. "What we found is that evolution might have taken a lot of different paths. Those became evolutionary paths not taken."

    The ability to re-create the precise development of the mutations on a protein -- the workhorses of cells -- is a milestone. Although scientists know there are different kinds of mutations, they hadn't clarified how one mutation builds on another.

    Redinbo said the study was undertaken to explore how proteins undergo minute changes. His lab, for example, looks at how proteins might protect humans from chemical weapons, such as nerve agents. Although the study was not designed for practical applications, it might one day help scientists develop protein-based therapies to treat illnesses.

    For now, the study's insight into the process of evolution provides a scientific alternative to one of the key principles of intelligent design, which accepts certain aspects of evolution but argues that some biological mechanisms are too complex to be adequately explained and must, therefore, have been created by an "intelligent designer."

    Daniel Weinreich, a professor in the department of ecology and evolutionary biology at Brown University in Rhode Island said the study's significance is that it shows the order of major and negligible mutations and how they follow on each other's heels.

    "This study helps someone who's undecided to appreciate that mutations, one by one, are yielding a benefit to the organism," he said.
     

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