Posted on 10/07/2006 9:08:18 AM PDT by PatrickHenry
Evidence for punctuated equilibrium lies in the genetic sequences of many organisms, according to a study in this week's Science. Researchers report that about a third of reconstructed phylogenetic trees of animals, plants, and fungi reveal periods of rapid molecular evolution.
"We've never really known to what extent punctuated equilibrium is a general phenomenon in speciation," said Douglas Erwin of the National Museum of Natural History in Washington, D.C., who was not involved in the study. Since its introduction by Stephen Jay Gould and Niles Eldredge in the 1970s, the theory of punctuated equilibrium -- that evolution usually proceeds slowly but is punctuated by short bursts of rapid evolution associated with speciation -- has been extremely contentious among paleontologists and evolutionary biologists.
While most studies of punctuated equilibrium have come from analyses of the fossil record, Mark Pagel and his colleagues at the University of Reading, UK, instead examined phylogenetic trees generated from genetic sequences of closely related organisms.
Based on the number of speciation events and the nucleotide differences between species in each tree, the researchers used a statistical test to measure the amount of nucleotide divergence likely due to gradual evolution and the amount likely due to rapid changes around the time of speciation.
They found statistically significant evidence of punctuated evolution in 30% to 35% of the phylogenetic trees they examined. The remaining trees showed only evidence of gradual evolution.
Among the trees showing some evidence of punctuated equilibrium, the authors performed further tests to determine the size of the effect. They found that punctuated evolution could account for about 22% of nucleotide changes in the trees, leaving gradual evolution responsible for the other 78% of divergence between species.
Pagel and his colleagues were surprised that rapid evolution appears to contribute so much in some lineages, he said. "I would have maybe expected it to be half that much," he told The Scientist.
The researchers also found that rapid bursts of evolution appear to have occurred in many more plants and fungi than animals. Genetic alterations such as hybridization or changes in ploidy could allow rapid speciation, Pagel said, and these mechanisms are much more common in plants and fungi than in animals.
"Their result is pretty interesting, particularly the fact that they got so much more from plants and fungi than they did from animals, which I don't think most people would expect," Erwin told The Scientist.
However, it's possible that the analysis could be flawed, because the authors didn't take into account extinction rates in different phylogenetic trees when they determined the total number of speciation events, according to Douglas Futuyma of the State University of New York at Stony Brook, who was not involved in the study. But "they've got a very interesting case," he added. "I certainly think that this warrants more attention."
According to Pagel, the results suggest that other studies may have misdated some evolutionary events. Dates derived from molecular clocks assumed to have a slow, even tempo will place species divergences too far in the past, he said, since genetic change assumed to take place gradually may have happened very quickly.
"These kinds of events could really undo any notion of a molecular clock -- or at least one would have to be very careful about it," Futuyma told The Scientist.
Well known evolutionary mechanisms could account for rapid genetic change at speciation, Pagel said. Speciation often takes place when a population of organisms is isolated, which means that genetic drift in a small population or fast adaptation to a new niche could induce rapid evolutionary change.
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[Lots of links are in the original article, but not reproduced above.]
Why don't you answer the "the latter"
Let's just see how EV likes his words quote mined:
"...quite conveniently ignoring ... the existence of ... the American republic and the rights of Americans ....
the Creator amounts to nothing ......."
There, how's that sound? What's that you say? It completely changes your meaning?
Do you really believe that any scienitfic theory must incorporate a reference to "The Creator", lest it be judged "atheistic" by You Who Know All?
The world is billions of years old
Life on earth is billions of years old
All of life on earth shares common descent
Evolution is a fact
The scientific theory of evolution is the best explanation of the fact of evolution yet found
There is no physical evidence of supernatural (Designer) intervention for the past several-million years
Please, give me your sources and also the ID proponents of these above statements.
Again, I support all of the specific scientific research of ID scientists. Behe, for example, simply focused on specific biochemical "machines" and revealed design not chance.
But please, enlighten me? Again, I don't believe Behe, for example, claims to be an expert of the age of the world;he is not a geologist. In the areas where Behe is an expert, his research does nothing to undermine a creationist view. His philosophical statements in other areas are irrelevant to me. Creationists are interested only in "real science" and ID scientists , as far as I know, are credible. So, your statements you attribute to ID scientists are meaningless to me unless they are backed up by their own research. But..I would appreciate your sources with specific quotes from from identified ID researchers who have made these statements. Otherwise, your post is a bunch of generalizations and dubious in nature.
Creationists do not deny micro-evolution as long as the definitions in the discussion are specific.
There we go. No charge for that.
If all men are created equal, they must have had a Creator, don't you think?
I haven't messed with the sense of what they wrote at all. You have.
The removal of reverence for God, the God of Abraham, Isaac and Jacob, and of our founders, leads to disrespect for the lives of those who have been created in His Image. The loss of all liberty soon follows. That's the pattern of history. And the Founders knew it, even before the massive evidence of the history of the last couple of hundred years was amassed.
Good thing. It was worthless.
I believe the scientific theory of evolution explains how human beings came to have their current form. I'm not going to explain the entire theory to you, but the very short version states that natural selection forces a change in the frequency of alleles within a population from one generation to the next. These changes give rise to all the biological diversity we see around us, including human beings.
That scientific theory does neither precludes the existence of of a creator god, nor does it lessen in the slightest the value of the human soul.
Now, can you tell me how *you* think human beings came to have their current form?
Why precisely do you think that the scientific theory of evolution is incompatible with the founding father's conception* of God? Seeing as how the theory of evolution does not address the matter of ultimate creation, it would seem to be disengenuous to suggest that it precludes someone from believing in a creator god.
*Leaving aside, for the moment, the reality that the founding fathers as a group did not possess a homogeneous idea of what exact role God played in the Universe.
I haven't messed with the sense of what they wrote at all. You have.
That's a lie. I haven't "messed with" any of their words. I'm trying to defend them from your twisting influence. It's okay. It's the least I can do for them.
And yet, it was an improvement. I guess that makes your original statement....less than worthless.
If the vast majority of the founders were here, and you told them that man and ape share a common ancestor, they would laugh in your face.
Then, when they figured out that you were serious, and that your views had gained the supremacy in American public life, they would be very concerned.
Why do you hate it so much when I simply print the simple words that lay the premise for our nation's founding?
You accuse my of "quote-mining." Zippety-do. I accuse you of undermining the basis of our free republic.
That's some talent you have there, speaking for not only ALL of the Founding Fathers (since they all thought alike), but God himself.
Needless to say, I disagree with your presumption.
And you're *still* a quote-miner.
You accuse my of "quote-mining." Zippety-do. I accuse you of undermining the basis of our free republic.
What arrogance you have. You accuse me of "undermining the basis of our free republic" (such drama!) because I pointed out that you custom-tailored one of the Founders sentences for selfish reasons. You compound this offense by lying about it: "I simply print the simple words that lay the premise for our nation's founding".
I think I'll change my Tagline!
Well-played (you basis-underminer, you)!
And if the vast majority of the founders were here, and they saw EternalVigilance's selfish alteration of their own words, I imagine they'd do something completely different in his face.
;)
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