Genetic evidence for punctuated equilibrium

The Scientist ^ | 06 October 2006 | Melissa Lee Phillips

[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.]

[SoldierDad]

What P.K. sent required a cut and paste (not a direct link), and the cut and paste didn't work for me. Thanks for the new link. I'll check it out when time permits.

[caffe]

Where did we come from?

[Thatcherite]

I'm a total young earth creationist and proud of it.

So in reality you disagree with the brilliant ID scientists about almost everything. Glad that's clear now.

[stultorum]

"If there is "empirical evidence" to support the contention of ToE that one animal species "evolved" into a completely different animal species, then please, by all means, provide the "empirical evidence".

There ain't any.

"Show me this has happened between two different species."

Never happened. It's all speculation.

[stultorum]

"Where did we come from?"

Evolutionists say we came from monkeys.

But there are no witnesses who have seen a monkey turn into a human, or a bird evolve into a dinosaur or a fish evolve into a moneky and then into a man.

There are no transitional fossils to prove the above.

[Coyoteman]

Evolutionists say we came from monkeys.

Humans and modern apes all evolved from a common ancestor many years ago. Monkeys split off well before that human/ape common ancestor.

There are no transitional fossils to prove the above.

1) Scientists don't deal in "proof" but in evidence. The evidence for the theory of evolution is overwhelming. Its only those who have closed their minds because of a narrow interpretation of scripture who refuse to see the evidence that is all around them.

2) No transitionals? Ha! This is a transitional. Note its position in the chart which follows (hint--in the upper center):

---

Fossil: KNM-ER 3733

Site: Koobi Fora (Upper KBS tuff, area 104), Lake Turkana, Kenya (4, 1)

Discovered By: B. Ngeneo, 1975 (1)

Estimated Age of Fossil: 1.75 mya * determined by Stratigraphic, faunal, paleomagnetic & radiometric data (1, 4)

Species Name: Homo ergaster (1, 7, 8), Homo erectus (3, 4, 7), Homo erectus ergaster (25)

Gender: Female (species presumed to be sexually dimorphic) (1, 8)

Cranial Capacity: 850 cc (1, 3, 4)

Information: Tools found in same layer (8, 9). Found with KNM-ER 406 A. boisei (effectively eliminating single species hypothesis) (1)

Interpretation: Adult (based on cranial sutures, molar eruption and dental wear) (1)

See original source for notes:
Source: http://www.mos.org/evolution/fossils/fossilview.php?fid=33

Source: http://wwwrses.anu.edu.au/environment/eePages/eeDating/HumanEvol_info.html

[stultorum]

"Humans and modern apes all evolved from a common ancestor many years ago.

But I've read on these threads that humans evolved from monkeys/apes. But now you're saying that humans did not evolve from apes, but from a common ancestor other than apes.

So, who/what is this common ancestor humans evolved from?

[Coyoteman]

So, who/what is this common ancestor humans evolved from?

Here is one idea:

Source

[stultorum]

Is that a flying saucer? LOL!

Maybe we came from space. Is that called spandermia, or some such?

[EternalVigilance]

Monkeys split off well before that human/ape common ancestor.

I guess that makes you "a monkey's uncle"!

[Coyoteman]

Is that a flying saucer? LOL!

Maybe we came from space. Is that called spandermia, or some such?

You asked:

So, who/what is this common ancestor humans evolved from?

I provided an answer. Did you fail to understand it, even though I provided it in graphic form?

[Texas Songwriter]

What science do you refer too?

[Coyoteman]

Monkeys split off well before that human/ape common ancestor.

See post #388.

[Texas Songwriter]

There is nothing in conservatism that opposes evolution. There is nothing in conservatism that opposes the idea that things were created.

Who is this intelligence which did the "creating" to which you refer?

[stultorum]

Gorilla, chimpazee and humans evolved from orangatang?

And, Gorilla, chimpazee, humans and orangatang evolved from gibbons?

I don't know if I read this right.

[EternalVigilance]

See post #388.

Even a monkey can draw lines.

[EternalVigilance]

"We hold these truths to be self-evident, that all men are created..."

- Thomas Jefferson

[stultorum]

The picture reminds me of similarity with a little book I read neons ago - "How to Lie with Statistics."

It still looks like a UFO to me.

[EternalVigilance]

New tagline...

[stultorum]

I like your new tagline. I like it a lot.

How do you like mine?