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.]
Works for me!
New tag line here too inspired by your user name.
No, you are reading it wrong. The diagram is a partial species "family tree" on its side. The ancestor species go where the lines join. They aren't named on the diagram, and are now extinct.
I'm not sure I understand your question. Are you asking how humans came to have their current form, or are you asking about the origin of life on earth?
The theory of evolution has everything to do with the former, and nothing to do with the latter.
You ought to be ashamed of yourself, but I'm sure you're not. In fact, I'm sure you're very proud of having totally ignored the answer you were given, and coming up with some ridiculous UFO line.
Juvenile, and trollish. Which previously banned creationist troll are you, anyway?
They just don't understand them.
Once a quote-miner...
Would you argue that Jefferson, and his co-writers of the Declaration, did not believe that the existence of the Creator was self-evident?
I understand it quite well. It's a representation of someone's belief system. Guess that means I'm not a descendent of monkeys, but a child of the Creator that the writers of all of our founding documents believed in...
I'm asking you a fairly simple question.
Your so lame! Seriously lame.
__"So in reality you disagree with the brilliant ID scientists about almost everything. Glad that's clear now."
That's a stupid deduction. I differ philosophically with some assumptions. However, their scientific findings certainly does not undermine creationism. Perhaps you could update me and share what scientific findings that specifically would give a creationist problems with ID?
Which "fairly simple question" are you asking? Are you asking how life originally came into being on the planet Earth, or are you asking how human beings came to have their current form?
As I said, the theory of evolution has nothing to do with the former, and everything to do with the latter.
Giving your disagreement an incorrect highflown motive and insulting me doesn't diminish the vast gulf of almost total disagreement between you and the brilliant ID scientists. You don't disagree with their assumptions, unless you are disagreeing with the scientific method. You disagree with the conclusions they have come to (and which they share with almost every other professional biologist in the world) from studying abundant data. Namely:
Again, those are conclusions, not assumptions. Only young earth creationists incessantly and dishonestly try to paint well-founded conclusions derived from following the evidence where it leads as assumptions.
However, their scientific findings certainly does not undermine creationism.
You don't think that the above scientific findings undermine creationism? Then you are happy to endorse all of the scientific findings listed above? I doubt it.
Perhaps you could update me and share what scientific findings that specifically would give a creationist problems with ID?
See the above list of scientific findings endorsed by the prominent brilliant ID scientists that stick in the craw of creationists. The sum total of ID is that because there are gaps in our knowledge we can speculate that sometime, somewhere, a Designer did something, but we don't know what, where, when, why, or how. Not a scientific statement, but a philosophical one, derived from ignorance, and leading nowhere. That is the extent to which the brilliant ID scientists disagree with the rest of science, that they wish to have that philosophical statement considered science too. A young earth creationist has no more in common with the ID scientists than she has with any other evolution supporting biologist who also believes that God created the universe and sacrificed Jesus for our sins (and there are many of those).
I doubt you do.
It's a representation of someone's belief system.
See? I told you so.
Guess that means I'm not a descendent of monkeys,
Nobody said you are, but then, you don't really understand the ToE.
but a child of the Creator that the writers of all of our founding documents believed in...
...which has nothing to do with the ToE.
What you're quite conveniently ignoring is that the existence of the Creator is implicit, self-evident, in this passage that defines what the American republic and the rights of Americans are based on.
The elimination of the Creator amounts to nothing more nor less than the eroding away of the footings upon which American freedom is based.
Wishful thinking on your part.
"Itis easy to ignore the words of someone I have such low esteem for."
Then why don't you do it?
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