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.]
It's true that the Republicans have recently acquired a large group of voters who seem to be woefully anti-science. These are mostly those who used to be dems until they were alienated by Lyndon Johnson, and Nixon reached out to bring them into our party. Before then, these people cheered wildly for the likes of William Jennings Bryan, and were happy populists who supported candidates like FDR. Now we've got them, they call themselves "conservatives." They're good, patriotic, religious folks who support the military, and that's fine.
But who knows what they really think about limited government, free enterprise, and other traditional Republican values? Some of them around here sound like theocrats, which is hardly anyone's idea of how this country should be governed. Anyway, the days of the democrats' hold on the Solid South are gone.
I like their votes, as it's good to have Republican majorities, but I don't welcome their attitudes about science. I guess if FDR could put up with them, so can we. As long as the tail doesn't wag the dog.
And the true revolutionaries, fighting the hardening of the arteries of the Biological Sciences Establishment, were not the creationists and IDers (who are merely hottentots enraged) but Eldridge and Gould. They took on the establishment with punk-eke and the establishment came down on them hard. But like all scientific revolutions, victory follows the evidence.
It gratifies me to see the evidence accumulating for punk-eke. It's a great addition to the Theory of Evolution and I liked it the minute I first read about it.
Punk eke takes on the establishment of The Gradual. Gould also took on the establisment of The Adaptive, although less formally, with his example of The Spandrels of San Marco and the Panglossian Paradigm: A Critique of the Adaptationist Programme, which also appeared in The Third Culture.
As for you, Patrick Henry, you are the greatist.
Let's not get carried away.
You're right about that, of course. And let's not forget about Kansas. I was thinking about the old democrat coalition that included the South, and that coalition no longer exists. The William Jennings Bryan constituency (populism) is far more extensive than the South -- and of course it wasn't 100% of the South either.
I rather like the latest iteration, which appears to be that the TOE can't be right because all the evidence supports it. Therefore, it's never been falsified.
I disagree. While it's true that science isn't necessarily politically liberal or conservative, it is nevertheless a strong tendency toward conservatism. By that I mean that change is never made for its own sake, new ideas are viewed with suspicion and must be demonstrably better, and usually a lot better than the old to be accepted.
"punctuated equilibrium" = pitiful excuse for lack of solid scientific evidence of evolution.
The only reason you even need the wildly outlandish "Punctuated Equilibrium" myth in the first place is because of the striking absence of evidence in the fossil record for a slow progression of evolution over millions of years. (*cue the usual flurry of weak evidence for such from the evo crowd*)
With this theory, you've crossed the line from science to pseudoscience...from physics to metaphysics...from the natural to the supernatural.
The leap of faith; the suspension of disbelief; required to believe in PE is truly mindboggling.
The problem is that, at least among the poll participants here, the dog is the cr/id supporting crowd. The scientists and science supporters seem to be the tail.
I had not expected that poll result to be as skewed as it was.
(Yes, I do remember the wording was about equal opportunity teaching)
you nailed it. well said.
Good grief. You have been posting on these threads for years.
Think of the vast array of information that has been presented to you.
1) You did not read any of it.
2) You did not understand it. (and yet never asked a question).
3) You are afraid this knowledge will somehow hurt your faith (pretty weak faith if that is the case).
4) You don't really believe what you write and you troll these threads for the fun of a food fight.
Well, which is it?
The problem is that your evidence is completely unconvincing.
Do you believe in "punctuated equilibrium"?
So you are saying it is #2. Ok then.
I do not believe in either evolution or punctuated equilibrium.
However, I do accept the evidence that creates these models of how nature works. Such is science. Science is not a "belief". It is a series of rigorously tested models (theories) that describe the universe. Theories do get refined as we learn or discover new things, however, the amount of evidence for a theory is a vast array indeed.
I can only hope that this is the forum where the creationist crazies can vent.
My faith runs deep, but it does not require "evidence" in the form of ID or the debunking of evolution. My awareness of creation, myself and my eternal soul provides plenty of proof of my place in universe.
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. (A restatement of the original unproven assertion of certitude.)
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.
*guffaw*
Do you believe that selectively boldfacing words in an article falsifies the theory of evolution?
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