Punctuated equilibrium

[DaneaFL]

You know things have changed a little since darwins time, right? Its been like 150 years! You dont think weve refined the theory at all as more evidence has emerged?

Darwin thought evolution was gradual because it made sense to him and because there werent many good fossils during his time.

Now weve found many more fossils showing much more drastic evolution than darwin ever predicted. We now think that slow genetic mutation probably has less of an effect on evolution than environmental conditions, hence puncuated equilibrium.

Things like the cambrian explosion are evidences of this.

I know you creationists think that if a theory is ever revised or corrected then it is obviously a completey wrong theory, but sorry, thats how science works.

Change is actually a good thing in science even though you cant understand why.

I know your basis for knowledge hasnt changed for thousands of years and somehow you think thats a good thing, but science on the other hand is constantly changing and correcting itself.

 

[juvenissun]

Source?

Your mind.

 

[juvenissun]

What reason do I have to think it is a problem? "Juvenissun made stuff up on a forum" is not a reason. Hence the request for citations.

If you don't have a problem, why do you need any citation?

 

[TLK Valentine]

If you don't have a problem, why do you need any citation?

To prove that you're not making this up dishonestly.

 

[juvenissun]

That is really wierd, because I could never understand how a series of catastrophies with global consequences such as the opening of the Deccan traps & a large piece of rock smashing into Mexico could result in many large lizards becoming extinct and is shirtly followed by an explosion in the diversity of mammals & birds as a result.

You may compare two curves:

1. rate of evolution during the period of "punctuation"
2. rate of environmental change during the same period. (this shows the speed of environmental re-equilibrium)

Then you will see the problem.

 

[TLK Valentine]

You may compare two curves:

1. rate of evolution during the period of "punctuation"
2. rate of environmental change during the same period. (this shows the speed of environmental re-equilibrium)

Then you will see the problem.

Show us the curves, and we'll see the problem.

But you can't, since you're just making it up as you go.

 

[RickG]

The rate of evolution IS the major problem.

The rate of evolution and the rate of environmental change/restoration can not be synchronized.

It is perfectly synchronized in the fossil record, that's why it's called punctuated equilibrium. You see juve, the reason I see and understand evolution is not through biological studies, it was through my concentrated field of paleoclimatology. The geologic record is full of abrupt climate changes followed by mass extinctions and then a burst of new, more diverse and complex life following these events. Events like extended global cooling or warming, bolide (impact) events, sea level changes, flood basalts (Siberian Traps), ocean acidification, anoxic events, the great oxygenation event, and plate tectonics.

Just like a puzzle, the border is complete and many of the prominent objects in the picture are have been fitted together. What is to be completed are the those pesky areas that reveal little definition, but slowly and methodically, more and more of the hard pieces are falling into place.

And no matter how hard AV tries fit that pesky "wabbit" into the precambrian strata, the piece just doesn't fit, no matter how hard he tries.

 

[Wiccan_Child]

Your mind.

 

[juvenissun]

It is perfectly synchronized in the fossil record, that's why it's called punctuated equilibrium. You see juve, the reason I see and understand evolution is not through biological studies, it was through my concentrated field of paleoclimatology. The geologic record is full of abrupt climate changes followed by mass extinctions and then a burst of new, more diverse and complex life following these events. Events like extended global cooling or warming, bolide (impact) events, sea level changes, flood basalts (Siberian Traps), ocean acidification, anoxic events, the great oxygenation event, and plate tectonics.

Just like a puzzle, the border is complete and many of the prominent objects in the picture are have been fitted together. What is to be completed are the those pesky areas that reveal little definition, but slowly and methodically, more and more of the hard pieces are falling into place.

And no matter how hard AV tries fit that pesky "wabbit" into the precambrian strata, the piece just doesn't fit, no matter how hard he tries.

OK, let's see an example:

Assume a big meteorite hit the earth. Then some species go extinct due to the "fast" environmental change.

1. before the impact, everything is in equilibrium
2. during the impact, nothing is in equilibrium.
3. the environment might be restored to equilibrium in, say, 10,000 years.

Now, the question is: during the time period of environmental rebalance, should there be "fast", "faster" or "much faster" pace of evolution for the survived species?

 

[Naraoia]

We now think that slow genetic mutation probably has less of an effect on evolution than environmental conditions, hence puncuated equilibrium.

I'm not sure know where you got that idea

If you don't have a problem, why do you need any citation?

You seem to think I have a problem. I want to know why.

 

[Naraoia]

OK, let's see an example:

Assume a big meteorite hit the earth. Then some species go extinct due to the "fast" environmental change.

1. before the impact, everything is in equilibrium
2. during the impact, nothing is in equilibrium.
3. the environment might be restored to equilibrium in, say, 10,000 years.

Just to give you a better idea of the time scale: for a severe extinction, it's more like several million years. After the largest extinction event ever, it may have taken over 15 million years for some ecosystems to go "back to normal".

Now, the question is: during the time period of environmental rebalance, should there be "fast", "faster" or "much faster" pace of evolution for the survived species?

What kind of question is that?

 

[sfs]

It is perfectly synchronized in the fossil record, that's why it's called punctuated equilibrium. You see juve, the reason I see and understand evolution is not through biological studies, it was through my concentrated field of paleoclimatology. The geologic record is full of abrupt climate changes followed by mass extinctions and then a burst of new, more diverse and complex life following these events. Events like extended global cooling or warming, bolide (impact) events, sea level changes, flood basalts (Siberian Traps), ocean acidification, anoxic events, the great oxygenation event, and plate tectonics.

What you're describing does not sound like PE to me. You're talking about adaptive radiations into ecological niches left empty after a mass extinction, or into new niches. PE is, at least primarily, a description of the ordinary process of speciation. Whether it actually does occur the bulk of the time is a matter of debate, but that was the claim.

 

[Naraoia]

What you're describing does not sound like PE to me. You're talking about adaptive radiations into ecological niches left empty after a mass extinction, or into new niches. PE is, at least primarily, a description of the ordinary process of speciation. Whether it actually does occur the bulk of the time is a matter of debate, but that was the claim.

I just went back to Teh Original, and it does hint at applying the PE concept to adaptive radiations. On pp110-111, regarding the conundrum of many echinoderm "classes" with only a few species, but the first sentence could apply to anything:

Since speciation is rapid and episodic, repeated splitting during short intervals is likely when opportunities for full speciation following isolation are good (limited dangers of predation or competition in peripheral environments, for example - a likely Lower Cambrian situation). When these repeated splits affect a small, isolated lineage; when adaptation to peripheral envrionments involves new modes of feeding, protection, and locomotion; and when extinction of parental species commonly follows migration of descendants to the ancestral area, then very distinct phenons with few species will develop.

(Incidentally, does anyone have a pdf of this paper that renders the text as text?)

 

[sfs]

I just went back to Teh Original, and it does hint at applying the PE concept to adaptive radiations. On pp110-111, regarding the conundrum of many echinoderm "classes" with only a few species, but the first sentence could apply to anything:

I think PE can apply to adaptive radiation, but my point was that simply observing adaptive radiation doesn't tell you whether change was occurring primarily during speciation or not. (My impression is that the definition of PE tended to be a bit slippery, depending on how they felt like applying it, so clear distinctions may not in fact be possible.)

 

[Naraoia]

I think PE can apply to adaptive radiation, but my point was that simply observing adaptive radiation doesn't tell you whether change was occurring primarily during speciation or not. (My impression is that the definition of PE tended to be a bit slippery, depending on how they felt like applying it, so clear distinctions may not in fact be possible.)

I see.

 

[NailsII]

OK, let's see an example:

Assume a big meteorite hit the earth. Then some species go extinct due to the "fast" environmental change.

1. before the impact, everything is in equilibrium
2. during the impact, nothing is in equilibrium.
3. the environment might be restored to equilibrium in, say, 10,000 years.

Now, the question is: during the time period of environmental rebalance, should there be "fast", "faster" or "much faster" pace of evolution for the survived species?

Luckily for us, there is a well documented one in the fossil record - it happened around 65-66 million years ago.
But it wasn't just the impact that killed off the dinosaurs (to name but a few of the species that perished - because it effected marine life as well).
Despite you trying to vastly over-simplify things, let's follow your little flow.
1. OK.
2. This would be the really interesting bit if you were to look into it. The ability of some animals to survive a global catastrophe (such as frogs) is quite remarkable.
3. This is of course the key bit.
After time, it is reasonable to assume that a large catastrophe would make some animals extinct. It would appear that large animals with long reproductive cycles are most likely to be affected, possibly because they tend to be larger in size, smaller in number and reproduce more slowly.
Large herbivores would not, in all likelyhood, have enough to eat if the trees have stopped growing due to years of dust clouds blocking out the sun.
Large predators which feed on large herbivores are likewise doomed.
So Tyrannosaurs and Apatosaurs are history.
Any animals which relied on these for their food, (ie scavengers which picked on T-rex's left-overs) or hunters of baby sauropods are in big trouble.
So this also means that animals which spent there lives hiding from these predators, or living in the shadow of these large herbivores are free to increase in number.
A good analogy here would be a ferral species; take rats in Australia for example. Their natural predators are not there, so they reproduce at a startling rate. Over time these animals will seperate, find and inhabit new niches and diversify into seperate species, then ultimately seperate families, orders and even classes of animals.

Their rate of evolution would effectively increase, although the rate of genetic change per generation would not change (this is not a contradiction, as the changing environmental pressures would not punish those with differing phenotypes as much as a heavily-predated environment would).
Also, recent research has suggested that key changes to genetic 'switches' can allow minor DNA changes to have massive phenotypical effects.
The new pressures they face would shape their evolution, as opposed to the old pressures which are now largely gone, and this causes the increase in diversity we see in the fossil record following large-scale climate effects.
This, in a nutshell, is punctuated equilibrium.
It is a fact, because it is a description of what we see in the fossil record.
Because it unifies facts and can be used to make predictions, it is also a scientific theory.

 

[juvenissun]

I'm not sure know where you got that idea

You seem to think I have a problem. I want to know why.

Because you ask for a citation.

 

[juvenissun]

Just to give you a better idea of the time scale: for a severe extinction, it's more like several million years. After the largest extinction event ever, it may have taken over 15 million years for some ecosystems to go "back to normal".

What kind of question is that?

You misinterpret the meaning of the 15 m.y. said in the article. It is not the time for the environmental re-equilibrium, But for the repopulation of a species. Also, the abnormally long period of the Permo-Triassic environmental change is not a good example to represent the general case of much shorter and dramatic change suggested by PE. The article said so many this and that species were lost. But, does it say any new species appeared during the same period of time? Obviously none. If so, where is the PE?

And this example illustrated exactly what my question is. The slow coming back of a species AFTER the quick environmental rebalance shows the asynchronization between the rate change of environment and the rate change of evolution.

 

[juvenissun]

Luckily for us, there is a well documented one in the fossil record - it happened around 65-66 million years ago.
But it wasn't just the impact that killed off the dinosaurs (to name but a few of the species that perished - because it effected marine life as well).
Despite you trying to vastly over-simplify things, let's follow your little flow.
1. OK.
2. This would be the really interesting bit if you were to look into it. The ability of some animals to survive a global catastrophe (such as frogs) is quite remarkable.
3. This is of course the key bit.
After time, it is reasonable to assume that a large catastrophe would make some animals extinct. It would appear that large animals with long reproductive cycles are most likely to be affected, possibly because they tend to be larger in size, smaller in number and reproduce more slowly.
Large herbivores would not, in all likelyhood, have enough to eat if the trees have stopped growing due to years of dust clouds blocking out the sun.
Large predators which feed on large herbivores are likewise doomed.
So Tyrannosaurs and Apatosaurs are history.
Any animals which relied on these for their food, (ie scavengers which picked on T-rex's left-overs) or hunters of baby sauropods are in big trouble.
So this also means that animals which spent there lives hiding from these predators, or living in the shadow of these large herbivores are free to increase in number.
A good analogy here would be a ferral species; take rats in Australia for example. Their natural predators are not there, so they reproduce at a startling rate. Over time these animals will seperate, find and inhabit new niches and diversify into seperate species, then ultimately seperate families, orders and even classes of animals.

Their rate of evolution would effectively increase, although the rate of genetic change per generation would not change (this is not a contradiction, as the changing environmental pressures would not punish those with differing phenotypes as much as a heavily-predated environment would).
Also, recent research has suggested that key changes to genetic 'switches' can allow minor DNA changes to have massive phenotypical effects.
The new pressures they face would shape their evolution, as opposed to the old pressures which are now largely gone, and this causes the increase in diversity we see in the fossil record following large-scale climate effects.
This, in a nutshell, is punctuated equilibrium.
It is a fact, because it is a description of what we see in the fossil record.
Because it unifies facts and can be used to make predictions, it is also a scientific theory.

I don't see how would that happen. The time for the environmental change is too short for any evolution to take place. After the environment is restored, the rate of evolution should still be normal.

If so, where is the PE?

 

[juvenissun]

I just went back to Teh Original, and it does hint at applying the PE concept to adaptive radiations. On pp110-111, regarding the conundrum of many echinoderm "classes" with only a few species, but the first sentence could apply to anything:

Originally Posted by Eldredge&Gould 1972
Since speciation is rapid and episodic, repeated splitting during short intervals is likely when opportunities for full speciation following isolation are good (limited dangers of predation or competition in peripheral environments, for example - a likely Lower Cambrian situation). When these repeated splits affect a small, isolated lineage; when adaptation to peripheral envrionments involves new modes of feeding, protection, and locomotion; and when extinction of parental species commonly follows migration of descendants to the ancestral area, then very distinct phenons with few species will develop.

That is the key question I have. WHY should the speciation become rapid during the dramatic environmental change? The key argument is that the time duration of the change is too short for any speciation to take place. When the environment restored, the force for the fast speciation also disappeared.