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Genetic evidence for punctuated equilibrium
The Scientist ^
| 06 October 2006
| Melissa Lee Phillips
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.]
TOPICS: Culture/Society; Philosophy
KEYWORDS: crevolist; junkscience; ntsa; obsession; punctuatedidiocy; speculation
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To: SoldierDad
I don't know what you believe, and I don't care what you believe. You can believe an any religion's creation story to your heart's content. Christian, Norse, Hindu, Lakota, whatever you want to believe, have at it. Just stop mischaracterizing actual science, ok?
When you say you "have yet to see" any evidence of transitional species (which is a fairly misleading term, but we'll avoid another semantic debate for now) I assume you haven't bothered to look, or you've shut your eyes any time you're in the same room as a the evidence.
In either event, let's put that issue to bed:
http://en.wikipedia.org/wiki/List_of_transitional_fossils
http://www.talkorigins.org/indexcc/CC/CC200.html
http://www.talkorigins.org/faqs/faq-transitional.html
To: Professor Kill
In either event, let's put that issue to bed: By not visiting, reading, and understanding the material at those links, it can still be claimed that evidence has not been seen. I suspect that it's not yet bedtime for this issue.
322
posted on
10/09/2006 11:11:12 AM PDT
by
PatrickHenry
(Unresponsive to trolls, lunatics, fanatics, retards, scolds, & incurable ignoramuses.)
To: SoldierDad
I am not interested your attempts to redefine "empirical".
323
posted on
10/09/2006 11:15:53 AM PDT
by
Thatcherite
(I'm PatHenry I'm the real PatHenry all the other PatHenrys are just imitators)
To: Professor Kill; SoldierDad
It is a marvellous position that allows SD to ignore the evidence. If two fossils are extremely similar then he can say that they are the same species. If they are different he can say, "They are just different species. Where is your proof that they are related?" All the while ignoring the strata they are found in, the fact that they can be arranged in sequences of gradual change that fit with those strata and their geographical location, the fact that successful predictions are made of findings ahead of time, etc, etc, etc.
324
posted on
10/09/2006 11:21:12 AM PDT
by
Thatcherite
(I'm PatHenry I'm the real PatHenry all the other PatHenrys are just imitators)
To: atlaw
PART 1 1. Introduction What is a transitional fossil? The term "transitional fossil" is used at least two different ways on talk.origins, often leading to muddled and stalemated arguments. I call these two meanings the "general lineage" and the "species-to-species transition": "General lineage": This is a sequence of similar genera or families, linking an older group to a very different younger group. Each step in the sequence consists of some fossils that represent a certain genus or family, and the whole sequence often covers a span of tens of millions of years. A lineage like this shows obvious morphological intermediates for every major structural change, and the fossils occur roughly
(but often not exactly) in the expected order.
Usually there are still gaps between each of the groups -- few or none of the speciation events are preserved.
Sometimes the individual specimens are not thought to be directly ancestral to the next-youngest fossils (i.e., they may be "cousins" or "uncles" rather than "parents"). However, they are
assumed assumed? to be closely related to the actual ancestor, since they have intermediate morphology compared to the next-oldest and next-youngest "links". The major point of these general lineages is that animals with intermediate morphology existed at the appropriate times, and thus that the transitions from the proposed ancestors are
fully plausible.plausible? General lineages are known for almost all modern groups of vertebrates, and make up the bulk of this FAQ. "Species-to-species transition": This is a set of numerous individual fossils that
show a change show me those fossils between one species and another. It's a very fine-grained sequence documenting the actual speciation event, usually covering less than a million years. These species-to-species transitions are unmistakable
when they are found. I have not yet been shown them - just HEARD about them Throughout successive strata you see the population averages of teeth, feet, vertebrae, etc., changing from what is typical of the first species to what is typical of the next species
of course there could be no other possible explanation for similarity of teeth, feet, vertabrae, etc. Sometimes, these sequences occur only in a limited geographic area (the place where the speciation actually occurred), with analyses from any other area showing an apparently
"sudden" change. could explain the idea of Creation Other times, though, the transition can be seen over a very wide geological area. Many "species-to-species transitions" are known, mostly for marine invertebrates and recent mammals (both those groups tend to have good fossil records), though they are not as abundant as the general lineages (see below for why this is so). Part 2 lists numerous species-to-species transitions from the mammals. Transitions to New Higher Taxa As you'll see
no, I don't "see" the transitions - just reading that they exist throughout this FAQ, both types of transitions often result in a new "higher taxon" (a new genus, family, order, etc.) from a species belonging to a different, older taxon. There is nothing magical about this. The first members of the new group are not bizarre, chimeric animals; they are simply a new,
slightly different species, barely different from the parent species. Eventually they
give rise to a more different species, which in turn gives rise to a still more different species, and so on,
until the descendents are radically different from the original parent stock. For example, the Order Perissodactyla (horses, etc.) and the Order Cetacea (whales) can both be traced back to early Eocene animals that looked only marginally different from each other, and didn't look at all like horses or whales.
(They looked rather like small, dumb foxes with raccoon-like feet and simple teeth.)and where are those fossils in between that has led to the "discovery" that whales and horses came from something that looked like a fox or raccoon? But over the following tens of millions of years, the descendents of those animals became more and more different, and now we call them two different orders.
Not exactly the convincing evidence that was "promised". Terms such as assumed and plausable don't strike much faith in the evidence as being definitive.
325
posted on
10/09/2006 11:27:41 AM PDT
by
SoldierDad
(Proud Father of a 10th Mountain Division Soldier fighting in Mahmudiyah)
To: SoldierDad
I have not yet been shown them - just HEARD about them I don't "see" the transitions - just reading that they exist
and where are those fossils in between
Wow. Now I *am* calling you ignorant. Willfully, proudly, boldly ignorant of the evidence put right in front of your face.
show me those fossils
Let's try this again, shall we?
http://en.wikipedia.org/wiki/List_of_transitional_fossils
http://www.talkorigins.org/indexcc/CC/CC200.html
To: Thatcherite; SoldierDad
Well, you certainly called that one.
To: Matchett-PI
The great thing is, if more people voted for a third party it would send a nice message to the two major parties to straighten up.
Your hateful insult at the end of your post has put this discussion at an end. If anything you are simply convincing me more that third party voting is the right thing to do.
328
posted on
10/09/2006 11:38:59 AM PDT
by
trashcanbred
(Anti-social and anti-socialist)
To: trashcanbred
I have a question for everyone here. Does believing in Evolution mean you cannot be a Conservative or even a Republican? It obviously means that you are in the majority. Haven't you noticed?
329
posted on
10/09/2006 11:55:16 AM PDT
by
DungeonMaster
(Man defiles a rock when he chips it with a tool. Ex 20:25)
To: SoldierDad
As I said, that article presents a good starting place. It is, however, apparent that you read very little of it.
It is equally apparent that you either (1) have some sort of handicap that prevents you from investigating anything on your own or (2) are too bloody lazy to look. I can think of no other explanations for your strangely juvenile demand to "show me those fossils" and your petulant complaint that "I have not yet been shown them - just HEARD about them."
Now, I'm going to suggest something radical here. Instead of responding to this and future posts with some variation of your happy refrain that "if them there scientists ain't got everything, they ain't got nothing," pick a specific set of transitionals identified in the link provided, and frame some alternative explanations for their existence that takes into account their age, taxonomic hierarchy, and morphological similarities and dissimilarities.
330
posted on
10/09/2006 12:18:22 PM PDT
by
atlaw
To: trashcanbred
So exactly what are you trying to say? I think we were discussing various scientific approaches to life and you were ranting about Pat Robertson?
331
posted on
10/09/2006 12:24:10 PM PDT
by
caffe
(W)
To: atlaw
... pick a specific set of transitionals identified in the link provided, and frame some alternative explanations for their existence that takes into account their age, taxonomic hierarchy, and morphological similarities and dissimilarities.![](http://www.salon.com/media/oj960927.gif)
They're bones! Old bones!
Nothing but bones!
You have no evidence!
332
posted on
10/09/2006 12:25:32 PM PDT
by
PatrickHenry
(Unresponsive to trolls, lunatics, fanatics, retards, scolds, & incurable ignoramuses.)
To: ItisaReligionofPeace
If evolution is true, how did the very first molecule appear in the universe?
This is a non-sequitur. The theory of evolution has no relevance to the means by which "the very first molecule" came to appear in the universe.
333
posted on
10/09/2006 12:33:26 PM PDT
by
Dimensio
(http://angryflower.com/bobsqu.gif <-- required reading before you use your next apostrophe!)
To: PatrickHenry
To label people
anti-science is such a smug broad brush stroke. The point is that one can engage successfully in many areas of scientific work without bowing down to neo-Darwinist macroevolutionary theory -- which still awaits some provable and repeatable evidence.
The other point is that Darwinist dogmatism is as anti-scientific as some strains of Bible-only discourse. The monolith of Darwinian theory should not substitute for Crucifix or Torah as something unassailable and sacred.
334
posted on
10/09/2006 12:34:58 PM PDT
by
Maeve
To: Maeve
What's "neo-Darwinist macroevolutionary theory"?
335
posted on
10/09/2006 12:38:20 PM PDT
by
atlaw
To: caffe
So exactly what are you trying to say? I think we were discussing various scientific approaches to life and you were ranting about Pat Robertson? A rant is when someone goes on and on about something, normally ad nauseam. How many times did I mention Pat Robertson? I mention Robertson only once and use him to prove the point that ID is Creationism, not science. I did not discuss Robertson at all in my post afterward. Therefore, I did not rant about him at all did I?
Nice spin... you avoided all the points I brought up by deceptively claiming my post was a rant about Robertson. I really don't like it when people pull that crap on me. I feel it is dishonest.
336
posted on
10/09/2006 12:52:51 PM PDT
by
trashcanbred
(Anti-social and anti-socialist)
To: Professor Kill
Your search - http://en.wikipedia.org/wiki/List_of_transitional_fossils - did not match any documents. Suggestions: Make sure all words are spelled correctly. Try different keywords. Try more general keywords. Well, that was useful. Shall we try a different link?
337
posted on
10/09/2006 12:58:21 PM PDT
by
SoldierDad
(Proud Father of a 10th Mountain Division Soldier fighting in Mahmudiyah)
To: Professor Kill
Your search - http://www.talkorigins.org/index/CC/CC200.html - did not match any documents. Suggestions: Make sure all words are spelled correctly. Try different keywords. Try more general keywords. Struck out there too.
338
posted on
10/09/2006 12:59:45 PM PDT
by
SoldierDad
(Proud Father of a 10th Mountain Division Soldier fighting in Mahmudiyah)
To: SoldierDad
339
posted on
10/09/2006 1:02:35 PM PDT
by
trashcanbred
(Anti-social and anti-socialist)
To: trashcanbred
If that doesn't work try entering "List of transitional fossils" in the search field on the left.
340
posted on
10/09/2006 1:03:26 PM PDT
by
trashcanbred
(Anti-social and anti-socialist)
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