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.]
Are you saying that atomic theory is not discussed in chemistry classes and that relativity theory is not addressed in physics classes?
But look at all the evidence they've got for Noah's Ark and the Flood! I mean, when you consider all of that, you've got to admit they've got you stumped.
</creationism mode>
Boy, you can say that again.
You are holding a scientific claim to a standard -- proof -- to which nothing in science is ever held.
If you want to pitch your tent on unverified "claims" in Science magazine, go for it.
This is how the evos manipulate the discussion. They, like the TOE they advance, decide what evidence fits their position.
Yep.
Your bold-faced words are important. They are why the theory of evolution is not a religion. Scientists rarely use words that don't indicate that "as far as we are able to assess something at this point....we think this is true."
Religion does nothing of the sort. It merely takes things on faith and believes them.
That, EV, is the difference. Your boldfacing merely makes it more clear that science is the "search" for information. There's nothing dogmatic about it, as there is in almost all religions. Science is searching for evidence, and then interprets that evidence. New evidence changes the interpretations.
Science thinks; religion believes.
The dogmatism was stated in the opening paragraph, and again towards the middle of the piece, as I pointed out.
Pure speculation, based on preconceived notions, masquerading as authoritative knowledge.
That we have so many fossils to examine is evidence of the enormous quantity of living things that have existed on this planet. It is, indeed, rare for an individual plant or animal to become fossilized. So many things have to happen in just the right way for it to happen.
Yet, there are fossils almost everywhere, if you know where to look for them. That means that, despite the difficulty in fossilizing a particular individual, there have been so vastly many individuals that we have a rich fossil record.
I hope that helps.
Are you saying that Elementary and Middle School students are being taught atomic theory and relativity? These areas are only briefly touched upon in High School (general coverage only). But the TOE is extensively taught in Middle and High School as the only mechanism in which life arose on Earth. That, plus the belief that modern human started off as a monkey, and then evolved into what we are today (which if nature decided that modern man was superior to the monkey, then why are there still monkeys?). It is in college that these ideas are extensively taught (as they should be).
I note that you still have provided absolutely no evidence that the claims are actually false.
So, fossils are rare = we have an extensive fossil record -seems contradictory to me.
"...as superiority is a relative concept requiring qualifiers to have meaning."
So, are you in favor of killing the white moose?
http://www.freerepublic.com/focus/f-news/1715411/posts
Did you answer the question? Do you believe in "punctuated equilibrium"?
Does my working in public education with Kindergarten through High School age students for the past 11 years qualify me in knowing what is being taught in our public schools? In science classes TOE is hammered into students (same experience I had when in Middle and High School). Noone is providing any curriculum as an alternative to TOE. Thus, it is extensively (and exclusively) being taught in public schools.
Your question has no relevance to my statement.
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