Is the theory of punctuated equilibrium a gamechanger for evolutionary biology?

[axocanth]

Ax, You and Parm are both well read in Phil of Sci, so I may have to sit on the sidelines for a while with this thread and just try to keep up. Occasionally I may ask for clarification. E.g. when one speaks of a challenge to evolutionary theory, it is helpful to ask what part. The bucolic banjo players specifically target speciation (we are divinely created not the great-grandchildren of monkeys, by gum!). IOW they direct their gap-toothed sneers at macroevolution while grudgingly acknowledging well-observed instances of microevolution, like darkening beetles. Punked Eek, otoh, challenged Darwin's (and Wallace's) slow and steady version (phyletic gradualism) with something quite different, rapid and infrequent cladogenesis. Calling the present body of theory Darwinism does seem silly, rather like calling modern physics Galileanism.

I'll quote Gould at some length shortly. Other PE exponents such as Niles Eldredge and Steven Stanley say very similar things. I'd just add first, for what it's worth, that all three are a delight to read, wonderfully clever and sophisticated men, such a breath of fresh air compared to the likes of Dawkins' naivete and simplemindedness (Parmalee's observation about certain scientists not thinking comes to mind). Indeed, I do wonder if Dawkins even understands the force of the PE critique of traditional Darwinism, as it is quite subtle, even philosophical in parts. As you'll see in the quotes below, Gould does too.

All quotes below, unless otherwise attributed, are from Gould's 2007 "Punctuated Equilibrium".


In a nutshell, what is this "profound departure" that Gould speaks of? Essentially this: The traditional view is that macroevolution is nothing but microevolution writ large; the former reduces to the latter. In other words, the forces that drive short-term, small-scale evolution can be extrapolated to explain all evolution, even the dramatic fish-to-TheVat type changes that we all intuitively think of as evolution, rather than the insignificant changes happening within populations of moths or finches that not even Creationists deny.

The PE mob say the opposite: macroevolution does not reduce to microevolution. Clearly, whether they're right or not, this is not being advanced as a "complement" or "extension" of traditional theory; it's a direct contradiction thereof.



First a mental-masturbatory pause . . .

We've recently been looking at the vexed issue of scientific realism vs antirealism, asking questions such as "Is dark matter real?" But what about species?

It's not entirely clear that even Darwin himself believed that species are real, suggesting in some places that they are nothing more than arbitrary sections on a continuum. Scholarly opinion differs on Darwin's view of this, while biologists themselves take different attitudes to the reality of species, at least among those who contemplate the issue at all. The two dozen or so competing "species concepts" vying for attention should also be a warning sign to readers. Even among biologists who affirm the reality of species (and some don't), there exists nothing like a consensus on what a species is.

Now, as everyone knows, one major tenet of PE theory -- the "trade secret" of paleontology -- is that what typically (not always) happens is this: In contrast to traditional Darwinian gradualism, species enter the fossil record abruptly, change little or not at all for a few million years, then disappear just as mysteriously.

But, punctuated equilibrium was never formulated as a hypothesis about great variability in anagenetic rates (which, indeed, everyone has long acknowledged). Punctuated equilibrium presents a specific hypothesis about the location of most evolutionary change in punctuational cladogenesis, followed by pronounced stasis. - p345

This realization allows for a complete reconceptualization of what species are. They are not only real, but they are individuals. This is the more philosophical part of PE doctrine that I alluded to above, and it takes a while to get your head around it.

Species are real insofar as they have a fairly well defined beginning (or birth, if you like), a well defined end (i.e. extinction), and a fairly stable "lifetime" in between, not unlike an individual organism (e.g. Louise the kitten) or a tornado, say.

To say that species are individuals is in contrast with the traditional view that species -- if real at all -- are more like sets constituted by their members. On the traditional view, every individual tiger is a member of the set tiger. On the PE view, in stark contrast, each individual tiger is a part of an individual whole: the species tiger, just as your head is part of your body, or each star is part of a galaxy, or each individual state is a part of an individual whole: the USA.

Traditional Darwinian gradualists would deny individuality to species by arguing that they are mere abstractions, names we give to segments of gradually transforming lineages. But under the punctuated equilibrium model, species are generally stable following their geologically rapid origin, and most evolutionary change occurs in conjunction with events of branching speciation, not by the transformation in toto of existing species. Under this model, therefore, species maintain the essential properties of individuals and may be so designated.

- S J Gould, essay "Challenges to Neo-Darwinism", found in "The Richness of Life", p 226

Now, being real and being an individual has its advantages, not least you can do stuff; you can play a role in the evolutionary drama, exactly analogous to that played by individual organisms in traditional theory. Species, just like individual organisms, have properties that are distinguished from the properties of each individual organism. Some species, for example, might have a wide geographical range, conferring an advantage to them in the survival game in the event of a localized meteor strike, say.

"The theoretically radical features of punctuated equilibrium flow from its proposals for macroevolution, with species treated as higher-level Darwinian individuals analogous to organisms in microevolution"

- S J Gould, essay "The Structure of Evolutionary Theory", found in "The Richness of Life", p 243

Here endeth the navel gazing.



This now leads to what PE exponents frequently speak of as an "uncoupling" or "decoupling" of macroevolution from microevolution, opening up an entirely new realm of research. You won't understand the large, significant, long term changes in the saga of life by applying the same principles as you do to finch beaks and changes in moth color frequencies, let alone characterizing evolution as something that happens to genes (Dawkins).

A new hierarchy now emerges wherein not only individual organisms are actors in this grand play, but individual species, and perhaps even higher taxa, are too.



to be continued . . .

 

[axocanth]

. . . continued from above. Here's Gould . . .

". . . in paleontology one almost never found [Darwinian gradual change]" (p2)

". . . and, eventually, to the full hierarchical model of selection as an interesting theoretical challenge and contrast to Darwinian convictions about the exclusivity of organismal selection" (p3)

"Those ideas forced me to question the necessary basis for Darwin's key assumption that observable, small-scale processes of microevolution could, by extension through the immensity of geological time, explain all patterns in the history of life--namely, the Lyellian belief in uniformity of rate." (p10)

"and, eventually, to the full hierarchical model and its profound departure from the exclusively organismal accounts of conventional Darwinism" (p6)

"... because the tale itself illustrates the central fact of the fossil record so well -- geologically abrupt origin and subsequent extended stasis of most species" (p19)

"Most importantly, this tale exemplifies what may be called the cardinal and dominant fact of the fossil record, something that professional paleontologists learned as soon as they developed tools for an adequate stratigraphic tracing of fossils through time: the great majority of species appear with geological abruptness in the fossil record and then persist in stasis until their extinction. Anatomy may fluctuate through time, but the last remnants of a species usually look pretty much like the first representatives. In proposing punctuated equilibrium, Eldredge and I did not discover, or even rediscover, this fundamental fact of the fossil record. Paleontologists have always recognized the long-term stability of most species, but we had become more than a bit ashamed by this strong and literal signal, for the dominant theory of our scientific culture told us to look for the opposite result of gradualism as the primary empirical expression of every biologist's favorite subject -- evolution itself." (p19)

"Rather, punctuated equilibrium refutes the third and most general meaning of Darwinian gradualism, designated in Chapter 2 of SET (see pp. 152-155) as "slowness and smoothness (but not constancy) of rate." Natural selection does not require or imply this degree of geological sloth and smoothness, though Darwin frequently, and falsely, linked the two concepts--as Huxley tried so forcefully to advise him , though in vain, with his famous warning: "you have loaded yourself with an unnecessary difficulty in adopting 'Natura non facit saltum' so unreservedly." The crucial error of Dawkins (1986) and several other critics lies in their failure to recognize the theoretical importance of this third meaning, the domain that punctuated equilibrium does challenge. Dawkins correctly notes that we do not question the second meaning of insensible intermediacy. But since his extrapolationist view leads him to regard only this second meaning as vital to the role of natural selection, he dismisses the third meaning--which we do confute--as trivial. Since Dawkins rejects the hierarchical model of selection, he does not grant himself the conceptual space for weighing the claim that punctuated equilibrium's critique of the third meaning undermines the crucial Darwinian strategy for rendering all scales of evolution by smooth extrapolation from the organismic level. For this refutation of extrapolation by punctuated equilibrium validates the treatment of species as evolutionary individuals, and establishes the level of species selection as a potentially important contributor to the macroevolutionary pattern." (p27)

"Eldredge and I proposed punctuated equilibrium in this explicit context--as a framework and different theory that, if true, could validate the primary signal of the fossil record as valuable information rather than frustrating failure" (p33)

"First, punctuated equilibrium secures the hierarchical expansion of selectionist theory to the level of species, thus moving beyond Darwin's preference for restricting causality effectively to the organismic realm alone (leg one on the essential tripod). Second, by defining species as the basic units or atoms of macroevolution--as stable "things" (Darwinian individuals) rather than as arbitrary segments of continua--punctuated equilibrium precludes the explanation of all evolutionary patterns by extrapolation from mechanisms operating on local populations, at human timescales, and at organismic and lower levels (leg three on the tripod of Darwinian essentials). Thus, as emphasized in the last section, punctuated equilibrium presents no radical proposal in the domain of microevolutionary mechanics--in particular (and as so often misunderstood), the theory advances no defenses for saltational models of speciation, and no claims for novel genetic processes. Moreover, punctuated equilibrium does not attempt to specify or criticize the conventional mechanisms of microevolution at all (for punctuated equilibrium emerges as the anticipated expression, by proper scaling, of microevolutionary theories about speciation into the radically different domain of "deep" or geological time). But punctuated equilibrium does maintain, as the kernel of its potential novelty for biological theory, that those unrevised microevolutionary mechanisms do not hold exclusive sway in evolutionary explanation, and that their domain of action must be restricted (or at least shared) at the level of macroevolutionary pattern over geological scales--for punctuated equilibrium ratifies an effective realm of macroevolutionary mechanics based on recognizing species as Darwinian individuals. In other words, punctuated equilibrium makes its major contribution to evolutionary theory, not by revising microevolutionary mechanics, but by individuating species (and thereby establishing the basis for an independent theoretical domain of macroevolution). (p58)

"Thus, the classic and endlessly fretted "species problem in paleontology" disappears because species act as well-defined Darwinian individuals, not as arbitrary subdivisions of a continuum" (p52)

"This hierarchical theory establishes the independence of macroevolution as a theoretical subject (not just as a domain of description for accumulated microevolutionary mechanics), thereby precluding the full explanation of evolution by extrapolation of microevolutionary processes to all scales and times.

In practical terms, the implications of punctuated equilibrium for evolutionary mode have strongly impacted two prominent subjects, heretofore almost always rendered by extrapolation as consequences of adaptation within populations writ large: evolutionary trends within clades, and relative waxing and waning of diversity within supposedly competing clades through time. Punctuated equilibrium suggests novel, and irreducibly macroevolutionary, explanations for both phenomena." (pp 60-61)

 

[James R]

Note also, Aron Ra immediately proceeds (31:00 - 33:00) to explain to his audience that his barely literate adversary, once again, doesn't know what he's talking about. Darwin's original theory has subsequently been "extended", other ideas have "contributed" to it, and have been "integrated". There has been no challenge to it except from toothless Kentucky hillbillies.

It's the old "united front" propaganda line. Nothing to see here, folks. All is well in Darwinism, oops, I mean the neo-Darwinian modern sexy super-duper extended no-flies-in-this-ointment synthesis.

Readers are left to ponder how Gould's "profound departure" (see post above) is to be reconciled with all this. A typo perhaps? A secret penchant for moonshine and banjos?

A little knowledge can be a dangerous thing, especially when one is taking others to task for a lack of humility.

Ra and Coyne are both correct that Darwin's original theory has been "extended". It has also been challenged, and it has survived all the challenges so far. To mock something you obviously don't know much about says more about you than it does about the theory.

Also, Gould's punctuated equilibrium is not the "profound departure" you seem to think it is. It was a big deal in the pop science press back in the 1980s, but it has largely been absorbed into the mainstream modern synthesis in the 40 years since then. In the 80s, Dawkins and Gould went back and forth about it in their pop-science books. There was, of course, also discussion and some debate in the peer-reviewed literature back then. The wash-out was that punctuated equilibrium is mostly just evolution-as-usual happening faster than usual, under the right environmental conditions. It is also something of an illusion brought on by the incomplete fossil record.

Ponder away, by all means.

 

[TheVat]

It is well hidden, apparently. It strikes me as superfluous. One can just ignore someone without having to formally announce it. Scrolling past does the job.

The wash-out was that punctuated equilibrium is mostly just evolution-as-usual happening faster than usual, under the right environmental conditions. It is also something of an illusion brought on by the incomplete fossil record.

This does not sound quite right to me. Do you have a citation for this?

 

[exchemist]

It is well hidden, apparently. It strikes me as superfluous. One can just ignore someone without having to formally announce it. Scrolling past does the job.




This does not sound quite right to me. Do you have a citation for this?

Just going by the Wiki article: https://en.wikipedia.org/wiki/Punctuated_equilibrium , it seems a fair enough description to me.

The essence of punctuated equilibrium, as I understand it, seems to be the idea of long periods of stasis, in most of the population, most of the time. This was in contrast to the previous assumption that change was gradual and continual. PE seems to propose that gene flow within dense populations of organisms tends to prevent even beneficial mutations from gaining traction. Steps leading to speciation may be mostly likely occur during specific periods, on the fringes of populations - which will tend to be at the extremes of the conditions suitable for the organism and thus where selection pressure will be most intense - where the damping effect of gene flow is weakest.

What PE emphatically does not suggest is any kind of saltationism, nor does it call into question Darwin’s principle of natural selection. Gould was, it seems, infuriated by the co-opting of PE, as popularised in the press, by idiot creationists, to suggest the theory of evolution was all wrong or in serious trouble.

There seems to remain debate as to the prevalence of PE, as opposed to the more gradual and continuous process envisaged before PE was suggested. At any rate it is not either/or, it’s probably a blend, it seems. Amusingly it seems those who emphasise gradualism are dubbed “creeps”, while those who see a bigger role for PE are dubbed “jerks”.

Some of the gradualists do indeed think it may just be the incompleteness of the fossil record that makes change appear more punctuated than it really is.

That’s my reading of it anyway, but I don’t pretend it’s my speciality.

 

[parmalee]

Some of the gradualists do indeed think it may just be the incompleteness of the fossil record that makes change appear more punctuated than it really is.

This is the part that has confused me. Is it that that the incomplete record might suggest a misleading timeframe, or is it more to do with insufficient info regarding stasis/change?

And didn't Dawkins essentially criticize Gould for writing too well? Obviously, there's more to it, but I recall there being something about Gould's writing being too "seductive" or something. Dennett addresses some of this in his Darwin book, and I think he also gets on about how Gould writes in addition to what he says.

 

[exchemist]

This is the part that has confused me. Is it that that the incomplete record might suggest a misleading timeframe, or is it more to do with insufficient info regarding stasis/change?

And didn't Dawkins essentially criticize Gould for writing too well? Obviously, there's more to it, but I recall there being something about Gould's writing being too "seductive" or something. Dennett addresses some of this in his Darwin book, and I think he also gets on about how Gould writes in addition to what he says.

I don't know the ins and outs of the rivalry between personalities. It seems that it was, and to some degree remains, controversial. It looks as if Gould may have written in such an accessible way that the press seized on it and rather ran away with the idea and sensationalised it, warping it in the process as they often do. This would probably have left the rest of the community exposed to being bombarded with sensation-seeking journo questions, e.g. "is Darwinism dead?" and so forth, to a degree that understandably annoyed them. But I'm only guessing. I have not delved into the history of it.

As for the question about the fossil record, obviously any attempt to reconstruct the evolution of any species is an exercise in joining the dots, so I've no doubt it's quite hard to resolve the issue of how long it takes for a given speciation process to occur. The fact that there still seem to be disagreements about it 50 years on is surely evidence of how hard it is to resolve, from the fossil record.

 

[axocanth]

This is the part that has confused me. Is it that that the incomplete record might suggest a misleading timeframe, or is it more to do with insufficient info regarding stasis/change?

And didn't Dawkins essentially criticize Gould for writing too well? Obviously, there's more to it, but I recall there being something about Gould's writing being too "seductive" or something. Dennett addresses some of this in his Darwin book, and I think he also gets on about how Gould writes in addition to what he says.

In response to recent posts above, a bit more on punctuated equilibrium theory.

We recently discussed some "myths of science" (see the linked article by William F. McComas in posts 406 and 407). Perhaps the greatest myth pertaining to evolutionary biology is the following: All scientists agree that macroevolution is nothing but microevolution writ large.

You'll see it perpetuated all over the place: Youtube science educators, other discussion sites, and even from the highest echelons of science itself (Dawkins et al). I noticed it being perpetuated on this site as soon as I joined, first reacting to it here ("Intelligent Design Redux", post 1165):

Intelligent design redux

Don’t bother to ask, until you you answer my questions Then answer this question. You maintain that humans do not have a common ancestor with other great apes. Yet the mutative fusion of 2 ancestral chromosome into human chromosome 2 has been demonstrated and thus, by your logic, must have...

sciforums.com

It usually crops up in the following context (as it does above). First, a Creationist says something about macroevolution not happening. Then, an ill informed defender of science tells him -- assume Aron Ra voice --that scientists do not even recognize the terms micro- and macro-evolution, they're just something made up by Creationists, he's an ignorant hillbilly who knows nothing about science, and that there is no difference between micro- and macro-evolution except for the longer timescales involved.

To emphasize, yes, there are plenty of scientists who believe this (that macro is just micro writ large), but there are plenty of other distinguished scientists who do not believe this, and not just in the PE camp! The "evo-devo" folks say similar things too sometimes (see link above for a quote).


The myth continues that PE is a theory concerned purely with the pattern of evolution, that is, the mode or tempo, with nothing new to say about the process of evolution, that is, the mechanisms responsible for evolutionary change. It did indeed start out that way. Gould et al initially challenged (yes, challenged) orthodoxy by arguing -- "what every paleontologist has always known" -- that the fossil record does not reflect what Darwinian gradualism would lead us to expect. We typically (it's a claim about relative frequencies, Gould emphasizes) do not see smooth transitions; what we see instead time and time again, indeed almost always, is a species changing minimally or not at all during its existence.

The term "stasis" was coined for the phenomenon, and since the time of Darwin it was explained -- or explained away -- as incompleteness of the fossil record, i.e., what we've been digging up (the sample) is not representative of the whole. By analogy, it's like having a theory that an urn contains mainly red balls and we keep pulling out black balls! Now if the urn is large enough, you can always explain this away on grounds of probabilistic bad luck: "We keep pulling out balls of a color that are not representative of the general pattern (i.e. mainly red balls). Just give us more time!"

Gould et al protest enough is enough! It's not bad luck; the theory is just wrong - the urn does not contain mainly red balls at all. They were hardly the first to have noticed. Paleontologists had always known this.

I have long found Simpson's style of evolutionary analysis inspirational. Until Simpson came along, if a paleontologist found that patterns of stability and change in the fossil record didn't jibe very well with the Darwinian canon, the conclusion was always the same: the record is to blame. Simpson taught us to take the fossil record more seriously as a direct reflection of evolutionary history. With appropriate caution, we should test our theories against the record, and not automatically conclude it is the record's fault when, time after time, predictions fail to be confirmed when we tackle pattern.

- Niles Eldredge, "Reinventing Darwin". p23

Read also posts 434 and 435 again in this thread. E.g. Gould . . .

Most importantly, this tale exemplifies what may be called the cardinal and dominant fact of the fossil record, something that professional paleontologists learned as soon as they developed tools for an adequate stratigraphic tracing of fossils through time: the great majority of species appear with geological abruptness in the fossil record and then persist in stasis until their extinction. Anatomy may fluctuate through time, but the last remnants of a species usually look pretty much like the first representatives. In proposing punctuated equilibrium, Eldredge and I did not discover, or even rediscover, this fundamental fact of the fossil record. Paleontologists have always recognized the long-term stability of most species, but we had become more than a bit ashamed by this strong and literal signal, for the dominant theory of our scientific culture told us to look for the opposite result of gradualism as the primary empirical expression of every biologist's favorite subject -- evolution itself.

PE was subsequently expanded to offer an alternative -- rival -- account to traditional orthodoxy on not only the pattern of evolution but the process, that is, the mechanisms responsible for evolution. Steven Stanley has a book on the subject by that very name: Macroevolution: Pattern and Process, well worth a look.

Amazon.com

PE adds nothing new to the mechanics of microevolution, but their radical new suggestion is that you cannot extrapolate from micro- to macro-evolution: it's not just "more of the same".




My own view of the whole brouhaha -- somewhat speculative of course -- is that Dawkins and Dennett are particularly nasty individuals, dirty rotten scoundrels the pair of them lol, at every opportunity trying to misrepresent, distort, downplay and discredit the rival view. Readers can make up their own minds, though I could not recommended Gould's 2007 "Punctuated Equilibrium" more highly for anyone interested. The book, published after Gould's death, is simply an excerpt from his monster 1000+ pages 2002 "The Structure of Evolutionary Theory" of the parts related to PE. Perhaps the most fascinating section of all is the final one where he drops the science and offers his personal reflections on the reception of the new theory: intelligent scientific criticism from some opponents (most welcome) and gross distortion and personal attacks from others (Dawkins, Dennett). Essential reading!

During the Chinese civil war of the 1930s and 40s, the ruling generalissimo Chiang Kai Shek complained of a "disease of the heart" (the Communist threat from within) vs. a "disease of the skin" (the Japanese threat from without). One can't help feeling Gould was torn between a similar tension: the internal disease of traditional Darwinism vs the external disease of Creationism. Internecine conflict within evolutionary biology plays into the hands of the enemy at the gate!

On the one hand, then, we see him speaking of a "new theory of evolution emerging", while in other places the talk is less Che Guevara!



To be continued . . .

 

[axocanth]

Continued from above.

Finally, a few more quotes from prominent PE and evo-devo exponents to consider (see also link to ID Redux above for more) . . .

But in the 1970s, paleontologists began to question Simpson's assertion that fully ninety percent of the evolutionary patterns between fossil species were of the slow, steady, gradual predicted by Darwin and his intellectual descendants.

- Niles Eldredge, "The Monkey Business", p73

Once a species has evolved and become established, it is not unusual to find that it persisted virtually unchanged for an additional five or ten million years--and sometimes even longer.

- Niles Eldredge, "The Monkey Business", p74

The difference is crucial: punctuated equilibria offers one line of evidence suggesting that perhaps the normal processes of natural selection (plus random genetic drift) that go on within species may not be appropriately extrapolated as a smooth extension to explain the existence of millions of species, in some 90-odd phyla, occupying the earth for some 3.5 billion years. Yet that is indeed the simple, central contention of the "modern synthesis": what goes on within species, especially natural selection modifying gene frequencies, is really all we need to know to explain and understand the history of life.

- Niles Eldredge, "Time Frames", p133

The decoupling of large-scale evolution from small-scale evolution led me to make the antireductionist statement that molecular genetics alone cannot explain large-scale evolution.

- Steven M. Stanley, "Macroevolution: Pattern and Process", p193

Now is an appropriate point at which to return to the question raised at the start of this chapter--is evolution scale-dependent? Studies of the proliferation of species within genera and families often suggest that macro-evolution is simply accumulated micro-evolution, with the addition of reproductive isolation. However, studies on the origin of novelties (in the realm of mega-evolution, and in the turtle case associated with the origin of an order) suggest that some things are not just accumulated micro-evolution.

Our conclusions, then, are that the origin of a novelty is at least sometimes not explicable through accumulated typical micro-evolutionary processes; and therefore that the relative frequencies with which evolution moves in one novel direction rather than a different one may be explicable in terms of developmental bias as well as in terms of selection.

"Evolution: A Developmental Approach", Wallace Arthur, pp282-284

 

[axocanth]

And didn't Dawkins essentially criticize Gould for writing too well? Obviously, there's more to it, but I recall there being something about Gould's writing being too "seductive" or something. Dennett addresses some of this in his Darwin book, and I think he also gets on about how Gould writes in addition to what he says.

Myth #2 of evolutionary biology: Gould was a gifted writer and popularizer of science, but he lacked any real depth.

No prizes for guessing where this one originates from!

Nothing could be further from the truth, at least in my opinion. A wonderfully sophisticated man, quite conversant in many topics already breached in this thread: philosophy of science, theory-laden observation, the influence of extra-scientific factors (e.g. social and cultural factors) on scientific work, and so on and so forth.

Dawkins, by contrast, boasts the depth of a puddle!

 

[James R]

This does not sound quite right to me. Do you have a citation for this?

You could start with this, from the wikipedia article on "punctuated equilibrium":

Punctuated equilibrium is often portrayed to oppose the concept of gradualism, when it is actually a form of gradualism.[64] This is because even though evolutionary change appears instantaneous between geological sedimentary layers, change is still occurring incrementally, with no great change from one generation to the next. To this end, Gould later commented that "Most of our paleontological colleagues missed this insight because they had not studied evolutionary theory and either did not know about allopatric speciation or had not considered its translation to geological time. Our evolutionary colleagues also failed to grasp the implication(s), primarily because they did not think at geological scales".[14]

Richard Dawkins dedicates a chapter in The Blind Watchmaker to correcting, in his view, the wide confusion regarding rates of change. His first point is to argue that phyletic gradualism—understood in the sense that evolution proceeds at a single uniform speed, called "constant speedism" by Dawkins—is a "caricature of Darwinism"[65] and "does not really exist".[66] His second argument, which follows from the first, is that once the caricature of "constant speedism" is dismissed, we are left with one logical alternative, which Dawkins terms "variable speedism". Variable speedism may also be distinguished one of two ways: "discrete variable speedism" and "continuously variable speedism". Eldredge and Gould, proposing that evolution jumps between stability and relative rapidity, are described as "discrete variable speedists", and "in this respect they are genuinely radical."[67] They assert that evolution generally proceeds in bursts, or not at all. "Continuously variable speedists", on the other hand, advance that "evolutionary rates fluctuate continuously from very fast to very slow and stop, with all intermediates. They see no particular reason to emphasize certain speeds more than others. In particular, stasis, to them, is just an extreme case of ultra-slow evolution. To a punctuationist, there is something very special about stasis."

 

[TheVat]

You could start with this, from the wikipedia article on "punctuated equilibrium":

Thanks, I'll try to get back to this tomorrow, as chaos currently reigns at the Vat house. If Gould is correct that "there's no such thing as a fish," then perhaps our houseguest cannot be compared to one vis a vis freshness.

 

[axocanth]

I've finished watching the Aron Ra vs. Subboor Ahmad vid (see post 425). All very interesting. Other members can form their own conclusions, though my own impression is that Ahmad (not arguing for Creationism) comes across as far more reasonable and well informed; Aron Ra, by contrast, grossly incompetent, dogmatic, arrogant, condescending, and perhaps most worryingly of all for those who are concerned about maintaining public confidence in science, untrustworthy. Consider:

31:15 - "Subboor is not one to accept that additional mechanisms have been discovered and integrated. He talks about there being completely new theories that are supposed to challenge the original theory. No. These new theories are being integrated with the original mechanisms."


Is this a reasonable response, do you think?

Niles Eldredge again (post 453):

The difference is crucial: punctuated equilibria offers one line of evidence suggesting that perhaps the normal processes of natural selection (plus random genetic drift) that go on within species may not be appropriately extrapolated as a smooth extension to explain the existence of millions of species, in some 90-odd phyla, occupying the earth for some 3.5 billion years. Yet that is indeed the simple, central contention of the "modern synthesis": what goes on within species, especially natural selection modifying gene frequencies, is really all we need to know to explain and understand the history of life.

We've already seen that this "simple central contention" of the modern synthesis has been challenged by both the PE and the evo-devo camps.


In his opening speech (first 30 mins) Ahmad also draws attention to something known as "The Third Way". For the uninitiated (including myself):

Noble and James A. Shapiro established The Third Way of Evolution (TWE) project in 2014. The TWE which is also known as the "Integrated Synthesis" shares many similarities with the extended evolutionary synthesis but is more extreme in its claims. The TWE consists of a group of researchers who provide a "Third Way" alternative to creationism and the modern synthesis. The TWE predicts that the modern synthesis will be replaced with an entirely new evolutionary framework. Similar to the extended evolutionary synthesis (EES), advocates cite examples of developmental bias, genetic assimilation, niche construction, non-genetic inheritance, phenotypic plasticity and other evolutionary processes. Shapiro's natural genetic engineering, a process described to account for novelty created in biological evolution is also important for the TWE. The difference between the extended synthesis and the TWE is that the latter calls for an entire replacement of the modern synthesis rather than an extension.

Denis Noble - Wikipedia

en.wikipedia.org

Are other readers familiar with this "Third Way"? Any thoughts? Are we to take it that Aron Ra is to be believed, and nothing mentioned above challenges the modern synthesis? What do other readers think?



Some other points of interest in the vid:

54:00 - Ahmad responds to Aron Ra's claim that American scientists don't use the word Darwinism at all (see post 425 for my own reaction):

"Sorry, I'm just not going to accept that. That's just the silliest thing I've heard in the last ten minutes. It's a duty upon you to do your research properly."

Indeed!

(Aron Ra responds again at 1:03:40)




Aron Ra 1:05:50 - "Genetics finally confirmed conclusively, if I may say so, absolutely, that humans are in fact apes."

Now, here's another one of these mantras that gets thrown around all over the place nowadays, the implicit quantum leap in logic typically skipped over without even a blink. Creationists object to it, of course, on the grounds that they do not believe humans are descended from apes. But even supposing we all grant -- for the sake of argument, if you like -- that it is simply a brute fact of the world that all of us are descended from apes or apelike creatures, how do you get from "humans are descended from apes" to "humans are apes"?

Clearly, at least without additional premises, it does not logically follow, any more than it follows that TheVat being descended from 17th century pirates entails that he himself is a pirate.

I ask readers to consider: On the assumption that humans are descended from apes (a brute fact of the world), is it also a brute fact of the world that humans are apes? Or is it instead a matter of taxonomic preference?

Granting that the facts of nature compel us to the conclusion that humans are apes, what fact or facts, if any, compel us to the conclusion that humans are apes?

Gosh, this might keep us occupied for the next year!

 

[axocanth]

For further reference . . .

Aron Ra at 1:09:00, immediately after impugning his interlocutor's honesty (as his type invariably does) . . .

"Evolution is not based on assumptions, there is no dispute of the fundamental ideas of Darwinian theory, and it damn sure is not speculative."

Is this a fair comment? Is this an honest comment?

 

[C C]

Clarifying punctuated equilibrium (pictures included)
https://evolution.berkeley.edu/more-on-punctuated-equilibrium/
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[exchemist]

Clarifying punctuated equilibrium (pictures included)
https://evolution.berkeley.edu/more-on-punctuated-equilibrium/
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Reading this it seems my summary in post 449 is not too wide of the mark.

 

[axocanth]

From the link posted by CC above:

Punctuated equilibrium is an important but often-misinterpreted model of how evolutionary change happens. Punctuated equilibrium does not:

• Suggest that Darwin’s theory of evolution by natural selection is wrong.
• Mean that the central conclusion of evolutionary theory, that life is old and organisms share a common ancestor, no longer holds.
• Negate previous work on how evolution by natural selection works.
• Imply that evolution only happens in rapid bursts.

Before proceeding, let me quote Gould and note my own sympathies in this regard. (Almost) everyone speaks of "The Theory Of Evolution", or the "neo-Darwinian synthesis" including members here, but it's extremely hard to know what exactly they're referring to. I'd be inclined to say either (i) there is no such thing, or (ii) if it refers to everything that contemporary biologists have to say on the subject of evolution, then insofar as these claims are mutually incompatible, the theory suffers from internal inconsistency and is thus false.

The great Ernst Mayr repeatedly emphasizes that it's essential to recognize that Darwin proposed not one but five theories, while philosopher of biology David Hull say this:

The justification for such claims would be easier if there were one set of propositions (presented preferably in axiomatic form) which could be termed the theory of evolution. Unfortunately, there is not. Instead there are several, incomplete, partially incompatible versions of evolutionary theory currently extant.

- David L. Hull, "A Matter of Individuality" (found in "Conceptual Issues in Evolutionary Biology")

The modern synthesis has sometimes been so broadly construed, usually by defenders who wish to see it as fully adequate to meet and encompass current critiques, that it loses all meaning by including everything.

- S J Gould, quoted in Dennett "Darwin's Dangerous Idea", p281

All these statements, as Robson and Richards also note, are subject to recognized exceptions -- and this imposes a great frustration upon anyone who would characterize the modern synthesis in order to criticize it.

- S. J. Gould, "Is a New and General Theory of Evolution Emerging?"





Bearing all this in mind, and referring back to the quote at the top, I would say the following (comments, criticisms welcome):


* If "The Theory" (whatever that is) maintains that the principal mechanism of evolution is natural selection acting on individual organisms then PE may well pose a challenge to the theory, It is agreed that natural selection is real and plays a role in microevolutionary mechanics, but PE argues that evolution at the macro level, or a great deal thereof, happens at the level of species. Indeed, it is sometimes claimed that species selection is not a form of natural selection at all. How all this might be quantified to determine the relative dominance of each, I have not the faintest idea.

In short, traditional theory holds that natural selection explains evolution at all levels. PE denies this. The Theory is wrong.



* Correct! As far as I'm aware, PE does not question the doctrine of common ancestry at all.



* Not true! Or at least, PE purports to negate this. Traditional theory -- at least according to Niles Eldredge (see post 462) -- maintains that natural selection (and other minor mechanisms) can be extrapolated from intra-species change (i.e. microevolution) to explain evolution at the trans-species level (i.e. macroevolution). PE disputes this. (Evo-devo does too.) Natural selection does not (fully) explain the larger, indeed the important, changes, the kind of evolutionary change that raises an eyebrow at all (fish-to-TheVat kind of thing).



* Again, it's hard to know what "The Theory" is, and what precisely it asserts. Eldredge again (see post 453):

But in the 1970s, paleontologists began to question Simpson's assertion that fully ninety percent of the evolutionary patterns between fossil species were of the slow, steady, gradual predicted by Darwin and his intellectual descendants.

If Simpson speaks for "The Theory", then PE says the theory is wrong. The vast majority of evolution does not happen in this manner. Gould emphasizes that the dispute is about relative frequencies: traditional theory says that evolution typically happens one way; PE says it does not.




Just to give an example of the confusion, Jerry Coyne (in "Why Evolution is True") and Douglas Futuyma (in his textbook "Evolution") characterize "The Theory of Evolution" quite differently. The latter characterizes the modern theory of evolution as that which explains "evolution", by which he means something like common descent, or Darwin's "descent with modification". Common descent, then, is not part of the theory. This is "the fact" to be explained by "the theory".

Coyne, by contrast, includes common descent in "The Theory".

 

[axocanth]

Notice that CC's article above makes no mention at all of what perhaps is the most radical claim of PE theory: Macroevolution does not reduce to microevolution.

How much more radical could a claim be? If the PE guys are right, then by analogy, traditional natural selection (and fellow less significant travelers), though real enough, explains only the tip of the iceberg, i.e. superficial, observable, and minor change. And who ever doubted that a flock of sheep or pigeons won't look quite the same if you come back in fifty years!

Meanwhile, that unobserved mass under the water -- far and away the most important evolutionary changes -- are left unexplained by traditional theory.

Natural selection, then, might be described as what was previously thought to be Robert de Niro in a starring role turning out to be nothing more than an insignificant extra.

But the dog stays. Capisce?

 

[Pinball1970]

Normally this would be my bag but I will sit this one out I think.

 

[C C]

Notice that CC's article above makes no mention at all of what perhaps is the most radical claim of PE theory: Macroevolution does not reduce to microevolution.

How much more radical could a claim be? If the PE guys are right, then by analogy, traditional natural selection (and fellow less significant travelers), though real enough, explains only the tip of the iceberg, i.e. superficial, observable, and minor change. And who ever doubted that a flock of sheep or pigeons won't look quite the same if you come back in fifty years! [...]

Is that fully implied in PE, or does it largely stem from views he added on later -- what he entertains in his last book, The Structure of Evolutionary Theory -- and various papers he published in the period in between the early '70s and the 2000s?

The Structure of Evolutionary Theory - Wikipedia

en.wikipedia.org

According to Gould, classical Darwinism encompasses three essential core commitments: Agency, the unit of selection (which for Charles Darwin was the organism) upon which natural selection acts; efficacy, which encompasses the dominance of natural selection over all other forces—such as genetic drift, and biological constraints—in shaping the historical, ecological, and structural influences on evolution; and scope, the degree to which natural selection can be extrapolated to explain biodiversity at the macroevolutionary level, including the evolution of higher taxonomic groups.

Gould described these three propositions as the "tripod" of Darwinian central logic, each being so essential to the structure that if any branch were cut it would either kill, revise, or superficially refurbish the whole structure—depending on the severity of the cut. According to Gould "substantial changes, introduced during the last half of the 20th century, have built a structure so expanded beyond the original Darwinian core, and so enlarged by new principles of macroevolutionary explanation, that the full exposition, while remaining within the domain of Darwinian logic, must be construed as basically different from the canonical theory of natural selection, rather than simply extended."

In the arena of agency, Gould explores the concept of "hierarchy" in the action of evolution (the idea that evolution may act on more than one unit simultaneously, as opposed to only acting upon individual organisms).​

Aside from a community of organisms becoming isolated from the main group, and thereby the new conditions allowing them to escape the "stasis" of the latter...

Environmental stability -- which includes reciprocal interactions of species (predator/prey and symbiotic relationships) -- could keep the potential developments of a species in check. Eventual disruptions in the ecological system (cataclysmic or not), along with extinctions, frees up microevolution with respect to the survivors, so that its "actual pace" might be revealed (then getting labeled "macroevolution"). In contrast to the illusion that it wallows around in stasis most of the time, due to prolonged environmental constraints.
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