There are two important lessons for creationists in this video. Let's hope they learn them.
1. The evidence for punctuated equilibria is based on thousands and thousands of fossils covering millions of years. It required a complete fossil record. It has nothing whatsoever to do with gaps in the fossil record. It's the exact opposite of gaps!
2. Evolution is observed when a single species splits into two species and that takes place over a relatively short period of time. "Relatively short period of time" does not mean that the new species poofs into existence. It means 50,000-100,000 years.
Whenever your creationist friends start lying to you about punctuated equilibria you can ask them to watch this video. You'd think that would stop them from spreading misinformation but then you realize that this video is 20 years old.
Facts don't seem to matter to creationists.1
1. In the interests of fairness, I should note that there are a great many evolutionists who also don't understand punctuated equilibria. I'm really posting this video for them and not for the creationists.
[Hat Tip: Greg Laden]
59 comments :
What the video says is that the "relatively short period of time" is 5,000 - 50,000 - 100,000 years.
I don't understand punctuated equilibrium. It's a cute term, yes, but I could never understand exactly what it is. Is it a theory or an description? And what exactly is it saying that justifies a new term? That there can be stasis? That "perfect" gradualist view can be wrong? That gross morphological changes can occur suddenly?
All of this seems trivial enough to me.
I find it difficult to grasp Punctuated Equilibrium when I think in terms of human evolution. I'm sure someone will correct me/help me on this but when looking at all the different species and subspecies of human primates (say, H. habilis onwards), it's hard for me to see anything but gradual change over time. I'm sure most are aware of the long list of 'species' discovered during this ~2.3mya period of human evolution and if you look at the differences between each species, they are sometimes quite trivial.
I know Dawkin's in his later book also sees that with human evolution there appears to be "no clear line of demarcation between an ancestral species and a descendant species" - Wikipedia, not from Dawkin's book
I haven't read much on P.E. at all so i'm not even entirely sure what it exactly consists of. It'd be great if someone could help explain in relation to my example of human evolution.
A description is similar to a hypothesis/theory in that it predicts/explains.
My understanding of punctuated equillibrium is that the fossil evidence shows that most phenotype changes happen fairly rapidly and then flatten out. Which is a result you get when running evolutionary heuristics - sooner or later the population ends up in a local maximum. It requires rare "accidents" (significant environmental changes, speciation, etc.) to get the optimization rolling again - which results in long periods of apparent stability.
So you could say "Who needs punctuated equillibrium? It's just a macro-phenomenon often following from the basics." But it's entirely valid to analyze these phenomena. And the better the term "punctuated equillibrium" aggregates the underlying processes, and the better defined the determinants for non-appliance are, the more justified the term is.
An example for excellent aggregation for electromagnetic emissions is the wave function. An example for excellent definition would be the Pythagorean theorem which applies for triangles iff they have a right angle.
DK says,
All of this seems trivial enough to me.
Interesting.
We have a situation where some very intelligent evolutionary biologists have developed a model that explains an important pattern in evolution. This explanation is widely discussed in the scientific literature and covered in the textbooks on evolution.
In 2011 there is no serious debate about the existence of punctuated equilibria and its consequences. However, evolutionary biologists are debating the frequency of the phenomenon. Is it the mode of evolution all of the time, most of the time or only in a minority of cases.
Meanwhile, you think this seems "trivial."
What's the proper conclusion you should draw?
Cameron says,
I find it difficult to grasp Punctuated Equilibrium when I think in terms of human evolution.
Most people do. Punctuated equilibria probably doesn't apply to primate evolution.
Dr says,
My understanding of punctuated equillibrium is that the fossil evidence shows that most phenotype changes happen fairly rapidly and then flatten out. Which is a result you get when running evolutionary heuristics - sooner or later the population ends up in a local maximum. It requires rare "accidents" (significant environmental changes, speciation, etc.) to get the optimization rolling again - which results in long periods of apparent stability.
The key to understanding punctuated equilibria is to always keep in mind that change is associated with cladogenesis—the splitting off of a new species. The new species shows new characteristics but the parent species remains unchanged. It's important to remember that the two species continue to exist side-by-side in the fossil record suggesting that they lived side-by-side in the same environment.
That observation, which is crucial, tends to rule out a lot of explanations of the pattern. For example, it seems unlikely that the morphological change was stimulated by the a change in the environment. Also, it's worth noting that for different lineages the "punctuated" part of the pattern does not occur simultaneously. One lineage undergoes cladogenesis and another in the same bedding plane doesn't. The second lineage speciates one million years later while the first lineage is in stasis.
There are some notable exceptions to this observation but it seems to be the most common pattern. What this means is that if there is environmental change it's likely to be be very local only affecting one lineage.
Another thing we need to be careful of is assuming that species reach "local maxima" where they are so perfectly adapted to their environment that no more change is possible. Some people like to explain stasis in that manner but that explanation doesn't hold up to critical analysis. There's no evidence showing that any modern species is sitting at the the very top of an adaptive peak so it's unlikely that our ancestors did either.
DR says,
So you could say "Who needs punctuated equillibrium? It's just a macro-phenomenon often following from the basics."
So we've reached the third stage of a new theory—the stage where people start to say that it's trivial and exactly what everyone expected all along!
Back in 1972, Eldredge and Gould wrote that the pattern of punctuated equilibria was just what one expected given modern theories of speciation. It's taken almost thirty years for evolutionary biologists to digest this claim and even today I'd guess that most evolutionary biologists reject puntuated equilibria.
Here's the problem with the conclusion that PE is the "expected" pattern. Not all lineages show the pattern of punctuated equilibria. There are still plenty of excellent examples in the literature (and textbooks) of slow gradual change and speciation by anagenesis. Gradualism isn't dead. It's just got competition.
If punctuated equilibrium and cladogenesis are the "expected" pattern then how do we explain why so many lineages don't conform to that pattern?
I was hoping we would see more of the practical aspects of this theory. In believe they described how the hypothesis of punctuated equilibrium would be tested in real, in-the-field cases in their original paper.
Most popular sources about it focus only o the introduction (what it is), but unfortunately we never get to see how paleontologists actually use it to find out things about real living beings from the past.
I think this could be a reason why people find punctuated equilibrium as something trivial, merely a description rather than an functional theory which can be used to do things.
Look, Larry, if yo want to say that I am an idiot then just say so. But if you do that, please also explain WTF P.E. actually means.
Because if it is something that says that certain things *can* happen, then I remain unimpressed. Primarily because I don't believe by 1972 anyone seriously insisted that there must always be "constant speedism". Most certainly it is not how I ever thought about it - and I never read that 1972 paper.
If P.E. is merely an observation then all is good. It's named, I personally cannot comment on whether it is real or not but I do believe it's very possible and thus very likely happens. You seem to suggest that discussing frequency of stasis is important. OK. I certainly don't claim that figuring frequency of stasis is trivial. What is trivial IMO is that stasis happens.
Finally, your argument from authority ("intelligent evolutionary biologists have developed a model ... covered in the textbooks on evolution") does not impress me. We both know how potent hype and marketing can be in science. My reading of the textbooks on evolution was long ago and rather shallow but I don't remember P.E. occupying a prominent place there.
So if P.E. is neither a statement that things can happen, nor a description of what has happened but rather a theory on how things happen and why, then I never actually saw that theory in printed form and don't understand it.
There's no evidence showing that any modern species is sitting at the the very top of an adaptive peak so it's unlikely that our ancestors did either.
So absence of evidence is evidence?
The problem with that formulation is that it's very difficult to imagine how one might go about collecting evidence to test the claim, or in fact what such 'evidence' would even look like. Therefore we have pretty much no idea whether any modern population is at a (presumably trait-specific) 'local optimum' or not. Therefore your asserted 'likelihood' for extinct populations must have been pulled per anum.
I can't help but see evolution working as both a static and dynamic process, and the full spectrum in between.
Isn't it true that a phenotype that is good at surviving in a stable environment isn't going to change as quickly as a phenotype in a abruptly changing environment.
Its seems like in a stable environment evolution works like a 'fine tuning sculptor' slowing chiseling away and making small improvements along the way. Things such as changing course and diverting from the herd, would might only cause slow static like changes. As long as the environment wasn't all that different.
Where as in an unstable environment, when an organism suddenly finds itself in a completely different environment the 'sculptor' puts away his chisel and pulls out an axe and chainsaw. The phenotype changes more rapidly.
Both these scenarios fit within the realms of natural selection and it seems there would be no reason to favor one over the other. Both appear to be correct.
So it seems to me that Punctuated Equilibrium is a fascinating observation, that has been incorporated into the ever expanding knowledge of evolution, an rightly so.
But it can't change the fact that there is a broad spectrum of evolutionary change. And I'm guessing no here is actually denying that.
Thanks for the corrections, Prof. Moran.
One clarification regarding your refutation of: "Who needs punctuated equillibrium? It's just a macro-phenomenon often following from the basics."
I specifically lined up that dismissal for refutation. Considering your snide and verboose response it apparently was quite the honey pot.
Yet I still think I did a fairly even-handed job at refuting it myself. Meaning that firstly the hypothetical quote was no straw-man (like "Who needs biology, physics explains everything"), and secondly that my refutation was entirely technical in language and correct.
BTW, Prof Moran, are there really critics saying "Obviously PE is expected."?
Sounds like a straw-man to me.
Rather I expect general skepticism like: "What is the hypothesis? What is the proposed mechanism? What are the requirements? Which falsifiable preditions follow?"
I'm sure that's covered in the publications you referred to. Sadly the movie clip didn't go into the proposed mechanism for PE.
Dk says,
So if P.E. is neither a statement that things can happen, nor a description of what has happened but rather a theory on how things happen and why, then I never actually saw that theory in printed form and don't understand it.
Punctuated equilibria are examples of what is observed in the fossil record. The theory of punctuated equilibria is an explanation of why it happens that way. The latest version of the theory is a modification put forth by Douglas Futuyma and adopted by Gould. It's difficult to summarize the modern theory in a few sentences. The essence, as I understand it, is that the act of speciation locks in certain alleles in a kind of founder effect. That's why change is associated with speciation.
There are certain implications associated with punctuated equilibria. For example, if the number of species keeps doubling in a given environment then extinction is the only way to restore the number. This means that species have to compete with each other and that leads to species sorting—a conclusion that is uncomfortable for the majority of evolutionary biologists.
Species sorting was the main point of Gould's last book, "The Structure of Evolutionary Theory." If you want to learn about punctuated equilibria and species sorting then that's one of the many places where it is written down.
Sven says,
The problem with that formulation is that it's very difficult to imagine how one might go about collecting evidence to test the claim, or in fact what such 'evidence' would even look like. Therefore we have pretty much no idea whether any modern population is at a (presumably trait-specific) 'local optimum' or not. Therefore your asserted 'likelihood' for extinct populations must have been pulled per anum.
I think you missed the point.
Quite a few people seem to think that stasis in the fossil record is trivial because as long as the environment remains constant the species won't evolve.
I was merely pointing out that such beliefs have a hidden assumption; namely that species normally become so adapted to their environment that further adaptation can't happen. There's no evidence that modern species are perfectly adapted to their environment. Therefore there's no good reason to assume that ancient species were in stasis because they could not adapt any further.
It's okay to postulate that species become perfectly adapted to their environment, therefore evolution stops and that explains stasis. It's acceptable as long as you state the assumption clearly as part of your hypothesis.
It's wrong just to assume that perfect adaptation is true. I think you agree that there's no rational basis for making such an assumption.
I think the assumption must be incorrect since I see so many examples of sloppy and inefficeint design at both the morphological and molecular levels. Apparently you don't see any species that look like they are only part way up the adaptive hill so you are prepared to entertian the possibilty that species can frequently be at the top of an adaptive peak.
scott asks,
Isn't it true that a phenotype that is good at surviving in a stable environment isn't going to change as quickly as a phenotype in a abruptly changing environment.
It's certainly a common assumption.
I'm not sure why you think this is relevant to punctuated equilibria. Please try and remember that following cladogenesis the unchanged parent species continues to exist and may even survive longer than the new species. It's hard to reconcile that with the idea that the change is associated with survival in a changing environment.
DR says,
Rather I expect general skepticism like: "What is the hypothesis? What is the proposed mechanism? What are the requirements? Which falsifiable preditions follow?"
I'm sure that's covered in the publications you referred to. Sadly the movie clip didn't go into the proposed mechanism for PE.
I'm a bit confused by your responses. Apparently you don't know anything about the theory of punctuated equilibria, is that correct?
This means that species have to compete with each other and that leads to species sorting—a conclusion that is uncomfortable for the majority of evolutionary biologists.
Uncomfortable? Why? Some BS politics again? I know a bit about debates on the unit of selection and can see why gene-centric view will oppose the idea of species sorting but you make it sound like there is something else going on here. (?)
Personally, I think species sorting and group selection in general make a lot of sense. One could probably reduce everything to individual genes but for macro-level effects it makes no more sense than describing bullet ballistics using statistical mechanics approaches.
Apparently "The Structure of Evolutionary Theory." is a difficult opus of 1464 pages. Is there something more deep than the NCSE video which is still fairly readable? A popular science book?
Anyone?
LM: I'm a bit confused by your responses. Apparently you don't know anything about the theory of punctuated equilibria, is that correct?
Yes. Your blog is helping incrementally though. :o)
I think you are under the impression that a band of intentional and self-satisfied ignoramuses is populating your blog. While in fact DK's or others comments are all about trying to learn.
DR asks,
Is there something more deep than the NCSE video which is still fairly readable? A popular science book?
If you're interested in evolution I suggest you invest in a textbook. Evolution 2nd ed 2009) by Douglas Futuyma is an excellent choice. He has a good description of punctuated equilibria.
If you want more detail on punctuated equilibria then your best bet is Genetics, Paleontology, and Macroevolution by Jeffrey S. Levinton (2nd ed. 2001).
The best of the trade books is The Pattern of Evolution by Niles Eldredge (1999). If you don't want that much information then read some of the contributions to Stephen Jay Gould: Reflections on His View of Life (2008).
Back in 1972, Eldredge and Gould proposed the observation of punctuated equilibrium as the paleontological phenomenon representing Mayr’s parapatric speciation. Therefore, it had to do with cladogenesis from the start. And it was proposed to account for the absence of observed speciation in the fossil record. It did not get much attention at the time, 1972.
Around 1978 or so, Gould (who has said many different things about punctuated equilibria at different times) said something like: ‘the phenomenon of punctuated equilibria shows revolutionary changes can occur; something we (I?) as Marxists find a cool idea”. Thereafter, the fat was in the fire, as this was taken to mean that punctuated equilibria represented a different biology. By now, we are back to standard biology, with PE as one of the things one can find in the fossil record. PE is a description of a fossil pattern.
Population geneticists have never cared much about PE one way or another: selective changes even if slow are fast in geological time anyway, and many people take stabilizing selection as the usual state of affairs on average even if year by year selection is going on – average in time showing in the geological record. Moreover, differences in ‘Tempo and Mode in Evolution” were part of the staple diet already by 1972.
Textbooks of evolution nowadays mention PE, but make not a big fuss over it, PE being just one extreme of a continuum of possibilities.
The importance of Gould in the development of evolutionary biology is one issue, patterns in the fossil record another. The patterns are varied, and speciation cannot often be pinpointed. The answer to the question of Gould’s importance, if that is what Larry Moran is about, is open – perhaps less than Larry Moran would like.
“So we've reached the third stage of a new theory—the stage where people start to say that it's trivial and exactly what everyone expected all along!” – The fuss about PE was rather artificial and manufactured, given the lack of fuss in 1972.
What the video says is that the "relatively short period of time" is 5,000 - 50,000 - 100,000 years.
Could someone explain the difference between "poof into existence" and evolve into existence in 5,000 years please?
Stasis, to me, is the most interesting component of their hypothesis. It's interesting that Gould/Eldredge explained the "stasis" part of their hypothesis via some form of developmental constraints (or "genetic and developmental coherences" in their words). This is problematic for a few reasons. First, it is vague, and second, within a developmental system, you need some sort of mechanism to maintain these coherences. This leads to a small paradox: some form of selection is necessary to produce the "nonselective" constraint that is invoked to explain stasis, as pointed out by Gunter Wagner and Kurt Schwenk. "Internal" stabilizing selection is the likely mechanism. It maintains functional/developmental interdependencies among characters, and this--ironically--is probably what Gould/Eldredge had in mind, though they didn't want to invoke "stabilizing selection" since it makes people think of a constant external environment in which the selection pressures are all external--environmental, ecological, or social--and all constant. Internal stabilizing selection, on the other hand, works in the "physiological and anatomical" environment and suppresses any perturbations to functional and/or developmental interactions among traits during ontogeny. It is the mechanism that produces developmental/genetic constraints. More recently, Estes and Arnold published a great paper in 2007 entitled: "Resolving the paradox of stasis: models with stabilizing selection explain evolutionary divergence on all timescales." They took several stasis-based datasets and fit different models in order to explain the data. Their paper and the papers by Schwenk/Wagner have convinced me that stabilizing selection, whether internal or external, plays a role in maintaining stasis.
And by the way. How do we know it could have been 5,000 years?
Surely the fossil record can not be that informative.
Perhaps it was 1 year. Who knows?
Apparently it could have been very, very fast.
Evolution theory, based on random mutation and natural selection, can never explain the actual facts.
^
You probably wrote that comment in ~5min. However, I don't know for sure that you didn't write that in .0001 sec.
Since a human can't type that fast, you must be a creationist spambot, and thus can be ignored.
Evolution 2nd ed 2009) by Douglas Futuyma is an excellent choice. He has a good description of punctuated equilibria.
So I borrowed it from one of the students. Initially, Futuyma has something like one page devoted to PE. It goes like this:
1. It's an observation and
2. it's a hypothesis that significant morphological change (that's my reading of "characters") is always associated with speciation.
He then hints that #2 sounds very wrong, which I agree with. That's about all there is. There are other mentions of PE in the Speciation and Macroevolution chapters but they are all in the context of how Eldredge & Gould idea of speciation is wrong.
This reading further reinforces my feeling that PE owes more to marketing than to anything else.
@rich lawler: re: Estes and Arnold paper.
Seems like a really good one. I really liked their conclusion because it fits so well with what I think is intuitively clear:
"Our results suggest that properties of the adaptive landscape (topography, stabilizing selection, peak movement) account for the alternation between stasis and bursts of evolution that is commonly observed in the fossil record."
Anonymous said "Evolution theory, based on random mutation and natural selection, can never explain the actual facts."
Funny that you keep chanting this, despite all of the evidence to the contrary that people have supplied you with in other threads.
One more example: there is strong evidence that mutation rate (ie the frequency of random mutations) affects the tempo of evolution. Bacteria with mutations that render replication more inaccurate have an advantage in adaptive experiments over "normal" bacteria of the same species.
http://www.ncbi.nlm.nih.gov/pubmed/20080608
Please. Read up on these things before soiling the comments with your dogmatic rants. The rest of us are trying to have a conversation about the science.
anonymous and the other Jim are getting panicky when they are confronted with the idea that evolution took place in 5,000 years. (And perhaps even less).
That fact is not explainable with the random mutation and natural selection explanation. So they insult me to distract from the facts which they do not want to acknowledge.
DK says,
This reading further reinforces my feeling that PE owes more to marketing than to anything else.
By your own admission, your "feeling" is based on ignorance of punctuated equilibria. In the second comment in this thread you said,
I don't understand punctuated equilibrium. It's a cute term, yes, but I could never understand exactly what it is.
I suggested that it might be a good idea to learn about punctuated equilibria so I referred you the Futuyma textbook where it is covered. (Isn't it amazing that it would be covered in a 2009 textbook if it was just an example of good marketing!)
You borrowed a copy of the textbook and this is your response,
Futuyma has something like one page devoted to PE. It goes like this:
1. It's an observation and
2. it's a hypothesis that significant morphological change (that's my reading of "characters") is always associated with speciation.
He then hints that #2 sounds very wrong, which I agree with. That's about all there is.
I assume you are referring to the coverage of punctuated equilibria on pages 93-96 and the following section on "Rates of Evolution."
Futuyma points out that, "'Punctuated Equilibria' refers to both a pattern of change and a hypothesis about evolutionary processes."
He illustrates the pattern with several examples and images and contrasts it with phyletic gradualism, which he also illustrates. I hope you found this helpful in understanding that the pattern exists.
Futuyma then points out that the association of change with speciation is consistent with peripatric speciation as described by Ernst Mayr. This kind of speciation is discussed in Chapter 17. I hope you found it useful to see how the pattern of punctuated equilibria fits with ideas of speciation.
Futuyma concludes that the association of change with speciation is "not widely accepted." That's probably correct, allthough the controversy is well beynod the stage where PE can be dismissed out of hand as simply marketing hype.
Futuyma then mentions one of the explanations of stasis advanced by Eldredge and Gould in their original paper. This is the idea that morphological change is inhibited by internal constraints. Futyma doesn't like this idea but that's okay because by the 1980s nobody else did either, including Eldredge and Gould.
There are other mentions of PE in the Speciation and Macroevolution chapters but they are all in the context of how Eldredge & Gould idea of speciation is wrong.
You are probably referring to the section on pages 586-590 where there's more discussion of rates of evolution in the context of punctuated equilibria. Futuyma accepts, of course, that the pattern of punctuated equilibria is a real pattern but he points out that adaptive evolution is not always associated with speciation..
The interesting part of punctuated equilibria is stasis. So, how do evolutionary biologists explain stasis? Futuyma explores three possible explanations, including his own contribution (Futuyma, 1987). He concludes with,
This last scenario leads to the perhaps counterintuitive conclusion that long-term evolutionary change is more likely to occur in relatively stable than in frequently changing environments.
This idea has been incorporated into the modern theory of punctuated equilibra as described by Gould inThe Structure of Evolutionary Theory.
It's a shame you didn't read that part. There's also a short section of species selection (p. 293) that's worth reading if you want to have an informed opinion.
Let's be clear about one thing, DK. I'm not expecting you to accept punctuated equilibria or stasis or any particular mode of speciation. However, I do expect people to be informed about ideas they reject, especially if those ideas are supported by a significant minority of respected evolutionary biologists.
I'm not expecting you to accept punctuated equilibria or stasis or any particular mode of speciation. However, I do expect people to be informed about ideas they reject,
But I don't reject it! By now it is evident to me that the dry residue from PE is an observation of a pattern. I already wrote that I believe that the pattern is real and I see see nothing wrong with the existence of stasis.
What I "reject" (too strong a word) is the supreme importance of the term "PE" and the theory that was originally put forward with it. Sure, sometime gross morphological change will be coupled with speciation. But there is no way it is a predominant mechanism.
I did read the stasis section and it mentions PE (as a theory, not pattern) again only in the negative light. Missed the group selection discussion though.
especially if those ideas are supported by a significant minority of respected evolutionary biologists.
Is there a Stephen Jay Gould fan club I can become a member of? :-)
Thank you for drawing attention to this video as well as pointing out that punctuated equlibria is not an exclusive mechanism. I can see why some evolutionary biologists are reticent to embrace this concept.
Oh, BTW, Larry:
Thanks for posting this! Like I said, I didn't understand what PE is beyond the observation of the pattern. Your post prompted some reading and thinking and now I do (you provably disagree though :-)). So it was a great post and I thank you very much for being very involved in the comments.
Larry, why don't you write a textbook on evolution?
You like the subject, you have already written a lot about it, you write about how others write about it, and you already have the experience of writing a successful textbook. You could make something interesting.
Honestly, I'd buy it.
@Physeter,
There's no way I could write a textbook that's as good as the ones on the market.
I'm going to write a trade book as soon as I finish this edition of my textbook. The working title is "Evolution by Accident."
Good to hear about the trade book!
Are there going to be special discounts for your loyal Sandwalk readers*? ;-)
* You, know, Sandwalk is much more interesting than that blog by the Myers guy.
And by the way. How do we know it could have been 5,000 years?
Surely the fossil record can not be that informative.
Perhaps it was 1 year. Who knows?
Apparently it could have been very, very fast.
Evolution theory, based on random mutation and natural selection, can never explain the actual facts.
Could someone please explain how the evolution of a new species can take place in 5,000 years?
I haven't waded through all the comments, so maybe this has already been said. But one significant aspect of PE is that it links morphological change and speciation events temporally. It also allows for daughter and parent species to co-exist, and even to compete. Finally, it makes it much easier for species selection to occur by granting species births, deaths, and lifespans of sharper delineation.
@Ryan Gregory,
You'd be surprised at how few people understand those simple points.
Virtually zero (0%) of creationists get it about punctuated equilibria but that's not a big surprise. What really shocks me is how few scientists and students know anything at all about punctuated equilbiria. And when they do, their knowledge is often closer to that of the creationists than the scientists.
It's not covered in the first year course at the University of Toronto because that course is titled Adaptation and Biodiversity. It doesn't cover population genetics or random genetic drift either.
For 99% of our life science student's that course is their only exposure to evolution.
Could someone please explain how the evolution of a new species can take place in 5,000 years?
When evolutionists talk about evolution they stress how it has millions of years to occur.
But evolutionists go strangely quiet when it comes to light from the fossil record that these changes actually occur in dramatically short periods of time.
@ Anonymous,
I can only guess that you might be a young earth creationist, pardon me if your not, I'm just basing my assumption on statements like this:
"When evolutionists talk about evolution they stress how it has millions of years to occur.
But evolutionists go strangely quiet when it comes to light from the fossil record that these changes actually occur in dramatically short periods of time."
Speciation can occur in a short period of time, maybe 1-2 years for some species, maybe hundreds of years for others. It may also take longer, like thousands of years, tens of thousands of years, and millions of years. It all depends on the many variables that a organism is subject to. So if you talking about a breeding pair of fruit flies that have for one reason or another been separated from their original population. It might not take long to evolve into another species, maybe 1-2 years. If your talking about a whale evolving from a land animal, it may take millions if not tens of millions of years. If your talking about a human evolving from a common ancestor with a chimpanzee it took millions of years.
Why don't you just type it into google, all the basic information can easily be found. Here I'll do it for you:
http://en.wikipedia.org/wiki/Speciation
I might want to make it clear to you that the fruit fly in my example isn't going to turn into a frog or any thing ridiculous like that. It will however evolve into a new species of fruit fly. And I suppose if given more time, say millions of years it may evolve into some other type of flying insect that doesn't resemble the original species.
And a monkey isn't going to give birth to human. These are some of the misconceptions creationist sometimes have. Like the infamous "crocoduck" that Ray Comfort and is sidekick Kirk Cameron use to debunk evolution. They have such a limited knowledge of the theory that it makes them look like fools, and you don't want to be one of those:
http://en.wikipedia.org/wiki/Speciation
Anonymous - if you're genuinely interested, polyploidy is a mechanism that can cause instantaneous speciation - and has been observed to do so in many lineages.
I am not a young earth creationist. In fact I am not a creationist.
> [PE] has nothing whatsoever to do with gaps in the fossil record. It's the exact opposite of gaps!
I would disagree, squeezing the gap does not somehow remove the gap. The question of interest being how do species normally appear--if the answer is "suddenly", then that's a gap, until this observation is explained.
But now that the time interval can be some thousands of years, we almost should be able to do this in the laboratory. As in produce dramatic changes in a short period of time.
This theory would seem to be directly testable.
scott posted:
"And I suppose if given more time, say millions of years it may evolve into some other type of flying insect that doesn't resemble the original species."
This is a bit disingenuous. Because it hides the fact that each step of that supposed evolution occurs in a dramatically short period.
By referring to "millions of years" it hides the central truth that punctuated equilibrium has shown us,concerning each step.
I expect people here to pretend not to get this point.
Sandwalk fans, Question. Can scientists show that the essential processes making up punctuated equilibrium’s mechanism actually lead to speciation and not extinction? In other words, are the risks of extinction significantly increased for a species when its population becomes disconnected (split off), and it encounters environmental changes and habitat fragmentation, which (I think) are central to the idea of punctuated equilibrium?
Thank you for that comment Denny. That is a very interesting and important point.
Denny writesa:
[A]re the risks of extinction significantly increased for a species when its population becomes disconnected (split off), and it encounters environmental changes and habitat fragmentation, which (I think) are central to the idea of punctuated equilibrium?
The answer, as always, is "it depends." Even in the allopatric speciation model you appear to be thinking of, when a population splits, each of the resulting populations may be large and self-sustaining. In the human species, large self-sustaining populations evolved in sufficient isolation over a few tens of thousand of years to develop numerous widely varied characters (varied enough that your deep ancestry can be tracked somewhat through analysis of your DNA), though not enough to eliminate the ability to interbreed.
The allopatric speciation model isn't by any means the only one consistent with PE. Quoting Gould:
[T]ens of thousands of years are usually available for the origin of full reproductive isolation between new species. Because times of this order are sufficient for almost any model of speciation (except "dumb-bell" allopatry, where a population splits into two roughly equal parts and each diverges slowly thereafter), punctuated equilibrium per se does not suggest or specify any particular mode of speciation.
If you're interested, you can read more on pp. 137-141 at
http://books.google.com/books?id=504iVZyopJ8C&pg=PA137#v=onepage&q&f=false
which is a piece Gould wrote, abridged to fit into magazine format.
Jud you have posted:
"Even in the allopatric speciation model you appear to be thinking of, when a population splits, each of the resulting populations may be large and self-sustaining."
This is a bit disingenuous because if the groups are large then the possibility of speciation decreases.
You can't have it both ways.
The point that Denny made is still completely valid.
Anonymous writes:
Jud you have posted:
"Even in the allopatric speciation model you appear to be thinking of, when a population splits, each of the resulting populations may be large and self-sustaining."
This is a bit disingenuous because if the groups are large then the possibility of speciation decreases.
You are precisely wrong.
Mutations not subject to selection move to fixation (genetic drift) at a constant rate irrespective of population size. Mutations subject to selection have an effect that rises in proportion to that of drift as population size *increases*. So larger population size with respect to fixation of mutations (thus speciation) is neutral in the situation of drift, and more favorable to adaptive mutations overcoming drift effects.
The mathematics for all this was worked out nearly a century ago. I'd have thought you might want to brush up on the facts before accusing someone else of lying. (You know that's what "disingenuous" means, right?)
Unless you meant something else altogether than what you wrote, I think you ought to apologize for your unwarranted accusation.
Can someone explain to Jud why I said:
"You can't have it both ways".
It will be helpful to look again at what Denny said:
"Sandwalk fans, Question. Can scientists show that the essential processes making up punctuated equilibrium’s mechanism actually lead to speciation and not extinction? In other words, are the risks of extinction significantly increased for a species when its population becomes disconnected (split off), and it encounters environmental changes and habitat fragmentation, which (I think) are central to the idea of punctuated equilibrium?".
It looks like people here do not know this subject all that well.
If a group is small it has a greater chance of speciation but a greater chance of extinction.
If a group is large it has a smaller chance of speciation.
Either way the chances are not good.
@Jud: "Mutations not subject to selection move to fixation (genetic drift) at a constant rate irrespective of population size."
Doesn't this contradict the known first three eigenvalues of the Wright-Fisher matrix (which are 1, 1, 1-1/2N), i.e. the fixation rate should be proportional to the inverse of the population size?
I've always thought that Wesley Elsberry's Talk.Origins Archive FAQ on P.E. was a good primer on the subject.
Ralf Muschall writes:
[Quoting me] - "Mutations not subject to selection move to fixation (genetic drift) at a constant rate irrespective of population size."
Doesn't this contradict the known first three eigenvalues of the Wright-Fisher matrix (which are 1, 1, 1-1/2N), i.e. the fixation rate should be proportional to the inverse of the population size?
Looks like the answer is no under conditions of drift (see below), and I believe if you look back at previous Sandwalk postings you can find Dr. Moran saying the same.
From the ubiquitous Wikipedia - the article on Fixation (population genetics):
Under conditions of genetic drift alone, every finite set of genes or alleles has a "coalescent point" at which all descendants converge to a single ancestor (i.e. they 'coalesce'). This fact can be used to derive the rate of gene fixation of a neutral allele (that is, one not under any form of selection) for a population of varying size (provided that it is finite and nonzero). Because the effect of natural selection is stipulated to be negligible, the probability at any given time that an allele will ultimately become fixed at its locus is simply its frequency p in the population at that time. For example, if a population includes allele A with frequency equal to 20% and allele a with frequency equal to 80%, there is an 80% chance that after an infinite number of generations a will be fixed at the locus (assuming genetic drift is the only operating evolutionary force).
For a diploid population of size N and (neutral) mutation rate μ, the initial frequency of a novel mutation is simply 1/(2N) and the number of new mutations per generation is 2Nμ. Since the fixation rate is the rate of novel neutral mutation multiplied by their probability of fixation, the overall fixation rate is [equation not reproducible]. Thus the rate of fixation for a mutation not subject to selection is simply the rate of introduction of such mutations.
Anonymous writes:
If a group is small it has a greater chance of speciation but a greater chance of extinction.
If a group is large it has a smaller chance of speciation.
Either way the chances are not good.
You keep saying that, but offering no evidence whatever in support.
In fact, simple population genetics mathematics clearly shows you're wrong, so you may as well be insisting that 2+2=5 for all the weight that carries. And if more contradiction of your - what? imagination? intuition? fantasies? wishes? - about the way speciation works were needed, I also cited an article by Gould himself directly contradicting what you've so repeatedly claimed.
So if you've got a basis for your claims, and all of population genetics and other work on speciation over the past 150 years is wrong, c'mon, let's see the positive evidence in support of your revolutionary ideas.
lee_merril wrote: "I would disagree, squeezing the gap does not somehow remove the gap. The question of interest being how do species normally appear--if the answer is "suddenly", then that's a gap, until this observation is explained.
But now that the time interval can be some thousands of years, we almost should be able to do this in the laboratory. As in produce dramatic changes in a short period of time.
This theory would seem to be directly testable. "
There are two problems here, first how creationists think PE was proposed (as an ad hoc explanation made possible by gaps in the fossil record, when it's in fact the opposite), and second and perhaps more importantly the poor understanding that creationists have of what is required to have "transitional forms" or a phylogeny between species, for that matter.
Whereas there are still and there will remain forever many gaps in the fossil record of intermediates between species, so much so when it's an instance of PE, these -- between species -- are rather trivial for the confirmation of evolution. Even disregarding the entire fossil record, the distribution of traits on the species "coincidentally" happens only in a peculiar and otherwise unlikely pattern that is compatible with the hypothesis of the species being all related through descent with modification in a huge evolutionary tree. You don't even need to compare with an alternate hypothesis (that the traits are designed according with functions), and even if you do, it does not stand up to minimal scrutiny. Even though traits perform functions, obviously, they are only present in a phylogenetic pattern, whereas one could reasonably expect things like some birds having bat wings and vice-versa, if not all organisms having only one type of wing, regardless of their (nonexistant) phylogenetic/taxonomic branch. Organisms could and would be expected to be more like the chimeras of mythology, because descent is the only thing that makes it impossible.
In part, because just as you implicitly stated, change near species-level is something readily observable. Dog breeds are a single species but differ to a degree that would otherwise justify the classification in several distinct species or even genera. That does not happen just because they're still all mutually fertile (albeit I doubt crossings between the most disparate breeds have ever been tried). Similarly we know of a great deal of morphological variation within a single species on nature (mostly on alternate morphs, eg. sexual polymorphisms, not only the difference between male and female but alternate males and/or females).
What (perhaps) remains to be better understood isn't the most evident morphological differences between species, but rather the more cryptic physiological differences that make hybrids incompatible.
And it's not even something that appears abruptly, as evident from things like ring species (if I'm not mistaken) and some hybrids between quite distant species, like lions and tigers (split about 4 mya, african leopards and lions only about 2 mya, and even then hybrids seem to be less viable), whose female hybrid can be fertile still.
But that's not really a big deal, something that remains to be explained in order to accept that the utterly obvious phylogeny of all living things is real,that species are modified descendants of their obvious relatives, rather than the whole pattern being just a huge coincidence, and organisms just arose as they are from magic mud.
What would really be surprising was if, despite of radical morphological changes between two populations that had split for millions of years, hybrids were always still perfectly viable. I guess that perhaps it's somewhat of a larger mystery how come some species deviate from the rule of being more morphologically restrict in adult forms and have such aberrant alternative morphs.
I am not a creationist, but I am skeptical of skeptic ability to analyze, this post is funny because it claims creationists deny facts, when this video said change happens at 5,000 years, the author 'leaves' that fact out, which the video clearly stated.
When you post a blog bustin on people who ignore facts, then you do it... you are the hog washin.
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