| Topic: |
Religions > Atheism |
| User: |
"maff" |
| Date: |
07 Apr 2006 04:38:34 AM |
| Object: |
Study, in a First, Explains Evolution's Molecular Advance |
Study, in a First, Explains Evolution's Molecular Advance
http://www.nytimes.com/2006/04/07/science/07evolve.html?_r=1&oref=slogin
By KENNETH CHANG
Scientists have for the first time demonstrated how a progression of
small changes in existing parts created a new piece of molecular
machinery.
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| User: "stoney" |
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| Title: Re: Study, in a First, Explains Evolution's Molecular Advance |
10 Apr 2006 12:55:04 PM |
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On 7 Apr 2006 02:38:34 -0700, "maff" <maff91@yahoo.com> wrote in
alt.atheism
Study, in a First, Explains Evolution's Molecular Advance
http://www.nytimes.com/2006/04/07/science/07evolve.html?_r=1&oref=slogin
By KENNETH CHANG
Scientists have for the first time demonstrated how a progression of
small changes in existing parts created a new piece of molecular
machinery.
April 7, 2006
Study, in a First, Explains Evolution's Molecular Advance
By KENNETH CHANG
By reconstructing ancient genes from long-extinct animals, scientists
have for the first time demonstrated the step-by-step progression of how
evolution created a new piece of molecular machinery by reusing and
modifying existing parts.
The researchers say the findings, published today in the journal
Science, offer a counterargument to doubters of evolution who question
how a progression of small changes could produce the intricate
mechanisms found in living cells.
"The evolution of complexity is a longstanding issue in evolutionary
biology," said Joseph W. Thornton, professor of biology at the
University of Oregon and lead author of the paper. "We wanted to
understand how this system evolved at the molecular level. There's no
scientific controversy over whether this system evolved. The question
for scientists is how it evolved, and that's what our study showed."
Charles Darwin wrote in The Origin of Species, "If it would be
demonstrated that any complex organ existed which could not possibly
have formed by numerous, successive, slight modifications, my theory
would absolutely break down."
Discoveries like that announced this week of a fish with limblike fins
have filled in the transitions between species. New molecular biology
techniques let scientists begin to reconstruct how the processes inside
a cell evolved over millions of years.
Dr. Thornton's experiments focused on two hormone receptors. One is a
component of stress response systems. The other, while similar in shape,
takes part in different biological processes, including kidney function
in higher animals.
Hormones and hormone receptors are protein molecules that act like pairs
of keys and locks. Hormones fit into specific receptors, and that
attachment sends a signal to turn on — or turn off — cell functions. The
matching of hormones and receptors led to the question of how new
hormone-and-receptor pairs evolved, as one without the other would
appear to be useless.
The researchers found the modern equivalent of the stress hormone
receptor in lampreys and hagfish, two surviving jawless primitive
species. The team also found two modern equivalents of the receptor in
skate, a fish related to sharks.
After looking at the genes that produced them, and comparing the genes'
similarities and differences among the genes, the scientists concluded
that all descended from a single common gene 450 million years ago,
before animals emerged from oceans onto land, before the evolution of
bones.
The team recreated the ancestral receptor in the laboratory and found
that it could bind to the kidney regulating hormone, aldosterone and the
stress hormone, cortisol.
Thus, it turned out that the receptor for aldosterone existed before
aldosterone. Aldosterone is found just in land animals, which appeared
tens of millions of years later.
"It had a different function and was exploited to take part in a new
complex system when the hormone came on the scene," Dr. Thornton said.
What happened was that a glitch produced two copies of the receptor gene
in the animal's DNA, a not-uncommon occurrence in evolution. Then, for
reasons not understood, two major mutations made one receptor sensitive
just to cortisol, leading to the modern version of the stress hormone
receptor. The other receptor became specialized for kidney regulation.
Dr. Thornton said the experiments showed how evolution could and did
innovate functions over time. "I think this is likely to be a very
common theme in how complex molecular systems evolved," he said.
Christoph Adami, a professor of life sciences at the Keck Graduate
Institute in Claremont, Calif. who wrote an accompanying commentary in
Science, said the research showed how evolution "takes advantage of
lucky circumstances and builds upon them."
Dr. Thornton said the experiment refutes the notion of "irreducible
complexity" put forward by Michael J. Behe, a professor of biochemistry
at Lehigh University.
Dr. Behe, a main advocate of intelligent design, the theory that life is
so complicated that the best explanation is that it was designed by an
intelligent being, has compared an irreducibly complex system to a
mousetrap. Take away any piece, and the mousetrap fails to catch mice.
Such all-or-none systems could not have arisen with incremental changes,
Dr. Behe has argued.
Dr. Thornton said the key-and-lock mechanism of a hormone-receptor pair
was "an elegant exemplar of a system that has been called irreducibly
complex."
"Of course," he added, "our findings show that it is not irreducibly
complex."
Dr. Behe described the results as "piddling." He wondered whether the
receptors with the intermediate mutations would be harmful to the
survival of the organisms and said a two-component hormone-receptor pair
was too simple to be considered irreducibly complex. He said such a
system would require at least three pieces and perform some specific
function to fit his notion of irreducibly complex.
What Dr. Thornton has shown, Dr. Behe said, falls within with
incremental changes that he allows evolutionary processes can cause.
"Even if this works, and they haven't shown that it does," Dr. Behe
said, "I wouldn't have a problem with that. It doesn't really show that
much."
Copyright 2006 The New York Times Company
--
Fundies and trolls are cordially invited to
shove a wooden cross up their arses and rotate
at a high rate of speed. I trust you'll
be 'blessed' with a cornucopia of splinters.
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| User: "maff" |
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| Title: Joseph W. Thornton |
08 Apr 2006 03:52:49 AM |
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maff wrote:
Study, in a First, Explains Evolution's Molecular Advance
http://www.nytimes.com/2006/04/07/science/07evolve.html?_r=1&oref=slogin
By KENNETH CHANG
Scientists have for the first time demonstrated how a progression of
small changes in existing parts created a new piece of molecular
machinery.
"Joseph W. Thornton" OR "Joseph Thornton"
http://news.google.com/news?num=100&hl=en&lr=&safe=off&q=%22Joseph%20W.%20Thornton%22%20OR%20%22Joseph%20Thornton%22&btnG=Search&sa=N&tab=gn
http://www.google.com/search?num=100&hl=en&lr=&q=%22Joseph+W.+Thornton%22+OR+%22Joseph+Thornton%22&ie=UTF-8&sa=N&tab=nw
http://www.google.com/search?q=%22Joseph+W.+Thornton%22+OR+%22Joseph+Thornton%22&btnG=Search+Directory&hl=en&cat=gwd%2FTop
http://groups.google.com/groups?q=%22Joseph+W.+Thornton%22+OR+%22Joseph+Thornton%22&start=0&scoring=d&num=100&hl=en&lr=&safe=off&
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