Gould and Macroevolution

[Almo]

That's where Gould comes in. You stated that the accumulation of micro changes causes macro evolution. Gould disagrees; he thinks there's an even bigger mechanism at work.

I'd like to know more about this. Briefly, what does he propose? I've read a few of his books, and I find him immensely clever.

Edit to list source:
This thread was split from:
http://206.225.95.123/forumlive/showthread.php?t=50276

And the source was BillHoyt.

 

[KingMerv00]

I'd like to know more about this. Briefly, what does he propose? I've read a few of his books, and I find him immensely clever.

What is the source of that quote?

To my knowledge, Gould was an evolutionist through and through. He merely had some issues with the RATE of evolution.

 

[hammegk]

In a nutshell:

Per zoologist Dawkins evolution *must* be by gradual, step-by-step, tiny stages, otherwise it couldn't happen at all.

Per paleontologist Gould the fossil record shows it didn't happen that way.

 

[Garrette]

Not really true, hammegk, though I am not remotely an expert on this.

My layman's understanding of Gould's "punctuated equilibrium" hypothesis is this:

1. A portion of a stable population becomes geographically isolated

2. The isolated population undergoes hereditary mutations in the same fashion as the non-isolated population

3. Environmental factors unique to the geographic area containing the isolated population select mutations in that population which, by chance, would be advantageous even outside the isolated area

4. The isolated population, with its new mutations, becomes un-isolated

5. The new, advantageous mutations, cause for the previously isolated popoulation to proliferate more successfully


The mutations themselves are really no less gradual than in other hypotheses, but the success of the mutated population appears sudden as it spreads out from its isolation.

More than that, I don't think Gould said that this mechanism is exclusive of other mechanisms for evolution.

I'll step back now and let the more educated posters rip this to shreds as I'm sure I've misstated quite a bit.

 

[Melendwyr]

Part of the hypothesis is the idea that species remain relatively stable for long periods of time. Then, when some condition changes dramatically, speciation events occur relatively rapidly.

Long periods of steady and subtle change broken up by wild evolutionary shifts: that's punctuated equilibrium for you.

For more information, see http://www.talkorigins.org/faqs/punc-eq.html

 

[hammegk]

Not really true, hammegk, though I am not remotely an expert on this.

I don't see your comments in any way negating mine.

Long periods of steady and subtle change broken up by wild evolutionary shifts: that's punctuated equilibrium for you.

"Wild evolutionary shifts" are not in Dawkins model sfaik (may I call his ideas The Latest-as-of-Today Theory of Neo-darwinist Evolution), and are exactly what Gould points out.


Yeah, I know, semantics & definitions.

 

[Jon.]

Part of the hypothesis is the idea that species remain relatively stable for long periods of time. Then, when some condition changes dramatically, speciation events occur relatively rapidly.

Long periods of steady and subtle change broken up by wild evolutionary shifts: that's punctuated equilibrium for you.

For more information, see http://www.talkorigins.org/faqs/punc-eq.html

It's probably worth pointing out here that "relatively rapidly" means that the "wild evolutionary shifts" take place over tens of millions, rather than hundreds of millions, of years. Also that this theory is not inconsistent with more gradual evolution. Punctuated equilibria is perfectly consistent with slow, gradual evolution. The much-ballyhooed "split" between Gould and Dawkins is nowhere near as deep, wide or important as many anti-evolutionists like to make it out to be. Just read Dawkins' A Devil's Chaplain if you don't believe me.

 

[Garrette]

I don't see your comments in any way negating mine.

Fair enough.

But it's this part that I really take issue with:

Per paleontologist Gould the fossil record shows it didn't happen that way.

AFAIK, Gould did not say this. He said the fossil record did not exclusively support this interpretation.

For the rest, read Jon's post. It said much better what I was trying to say.

 

[sphenisc]

It's probably worth pointing out here that "relatively rapidly" means that the "wild evolutionary shifts" take place over tens of millions, rather than hundreds of millions, of years. Also that this theory is not inconsistent with more gradual evolution. Punctuated equilibria is perfectly consistent with slow, gradual evolution. The much-ballyhooed "split" between Gould and Dawkins is nowhere near as deep, wide or important as many anti-evolutionists like to make it out to be. Just read Dawkins' A Devil's Chaplain if you don't believe me.

It is substantially deeper than you make out.

Under Gould on Richard Goldschmidt
http://www.stephenjaygould.org/people/richard_goldschmidt.html

'major structural transitions can occur rapidly without a smooth series of intermediate stages'

 

[William Parcher]

'major structural transitions can occur rapidly without a smooth series of intermediate stages'

Rapidly as revealed by the fossil record, or rapidly in real-time? Either would seem to be using the term "rapid" in a relative way.

That statement would lend itself to grand misinterpretation.

 

[Roboramma]

Has Gould suggested a mechanism for evolution other than the familiar ones of Natural Selection and genetic drift?

I don't think he's a saltationist.

It seems that he's saying that under extreme environmental pressure, populaitons diverge much faster than usual, to the point that you don't see the intermediates in the fossil record - because the process is happening too fast. That doesn't mean that those intermediates don't exist.

But that's my understanding of him. I'm no expert on Gould. Could anyone bring in a quote to show him saying something different?

 

[Melendwyr]

No, he's not presenting any fundamentally new evolutionary mechanisms. His work is an elaboration on earlier ideas about how speciation takes place.

 

[sphenisc]

It seems that he's saying that under extreme environmental pressure, populaitons diverge much faster than usual, to the point that you don't see the intermediates in the fossil record - because the process is happening too fast. That doesn't mean that those intermediates don't exist.

But that's my understanding of him. I'm no expert on Gould. Could anyone bring in a quote to show him saying something different?

He's saying "macroevolution is not simply microevolution extrapolated, and that major structural transitions can occur rapidly without a smooth series of intermediate stages."

That is: specifically denying macroevolution is microevolution writ large. It also states 'without a smooth series of intermediate stages', not that they can't be seen in the fossil record; that they don't exist. The rest of the section makes it clear that this is what is intended.
The examples under 'The Return of Hopeful Monsters' (boid snakes and pocket gophers) explain the problem with any intermediates.

This seems to be saltationism.

 

[Melendwyr]

This seems to be saltationism.

Nope. You can get startling deviations from the previous design with just a few mutations in a single generation. Of course, that's usually lethal.

Read talk-origins more carefully, please.

 

[William Parcher]

At least one of Dawkins' criticisms of Eldridge & Gould's PE theory is that it can cause a person to think saltationism, instead of thinking rapid gradualism.

 

[sphenisc]

Nope. You can get startling deviations from the previous design with just a few mutations in a single generation. Of course, that's usually lethal.

Read talk-origins more carefully, please.

From talk-origins
"Saltationism (in texts before about 1940 also called "Mutationism" or "Mutation Theory", the view that changes between forms occur all-at-once or not at all) "

 

[Melendwyr]

That's not what Gould is saying at all. Speciation is the issue, not change-between-forms. In Gould's hypotheses, new species most frequently arise when sudden changes in environment cause small, isolated groups to experience different selection pressures than the main population. Selection works most rapidly on smaller populations.

 

[sphenisc]

That's not what Gould is saying at all. Speciation is the issue, not change-between-forms. In Gould's hypotheses, new species most frequently arise when sudden changes in environment cause small, isolated groups to experience different selection pressures than the main population. Selection works most rapidly on smaller populations.

To whom was that addressed? The issue was "You stated that the accumulation of micro changes causes macro evolution. Gould disagrees", see OP.

 

[Garrette]

Sphenisc, I think Melendwyr's comment works as a reply to the OP and to other posts suggesting that Gould was trying to overthrow gradual speciation.

He wasn't. He was offering a modified interpretation.

 

[Roboramma]

3. Environmental factors unique to the geographic area containing the isolated population select mutations in that population which, by chance, would be advantageous even outside the isolated area

4. The isolated population, with its new mutations, becomes un-isolated

5. The new, advantageous mutations, cause for the previously isolated popoulation to proliferate more successfully

So basically, you won't see this evolution in the fossil record because it's happening on such a small scale that there are very few intermediates and they would be very unlikley to fossilize. But after this new form spreads out, and proliferates, it becomes very common and much more likely to fossilize. Thus you see it's appearance in the fossil record as sudden.

Sorry sphenisc to have disregarded your last post, but, well, this is what I thought Gould was saying before. Can you give me a reason to change my opinion?