Another dismissed form of evolution, hybridization, shows at least some viability

Z: Cecal values are a paeodomorphic characteristic Thought we had read that the cecal valves were found in the embryonic form, but we haven't been able to locate the paper, or if our memory is faulty. We retract this statement for now. Zachriel

As to the Adriatic lizards, if you calculate the effective population size, and you consider the numbers present 35 generations later, this is not enough time for the population as a whole to sample the entire genome; probably only a thousandth, or ten-thousandth of it. (IOW, not even ONE needed mutation will likely show up) So why do you give such a seemingly “learned” answer when you know full well that population genetics can’t even begin to give an answer. How is this being intellectually honest?

This is one of those cases where knowing what you are talking about is an advantage. There is no requirement for "all of the genome to be sampled" for a mutation to be selected for, I don't know where you got that idea. If, as Zach suggests, the cecal valves are a trait retained from a juvinal stage then it's possible all you'd need to have the trait survive into adulthood is a mutation that prevented a cis-regulatory sequence from matching a transcription factor. Of course, to actually understand the evolutoin of the trait you'd have to get our of your armchair and do some science. Evolutionary biology gives us tools to do that, including pop. gen. and quant. gen. What does ID have to offer.

Where do I begin? What is the “modern understanding of speciation”?

Coyne and Orr (2004) would be a good starting point for you to learn. There are also > 700 arcticles in google scholar for the term "speciation with gene flow"... Macroevolution is something different than speciation.

Yes, Darwin’s principle of Divergence is about ecological competition. And it involves progeny of the parent species ‘replacing’ the parent species in the changed environment because they are now “more fit”. And without that, you will never have macroevolution because, as in the case of dogs and wolves, all the change that takes place within species can always simply “revert,” just as in the case of those Darwin’s Finches that “fuse” together, and don’t replace the original species. And Darwin knew this better than everyone else.

There are tonnes of well studied cases of speciation including ecological competetion. So I'm not sure what your point is. Moreover,ecological competition is not requirement for speciation, geographical or temporal isolation will do the trick too. This is all a bit strange though, do you deny speciation happens? Or do you think speciation events are themselves the result of divine intervention? wd400

PaV: As to the Adriatic lizards, if you calculate the effective population size, and you consider the numbers present 35 generations later, this is not enough time for the population as a whole to sample the entire genome; probably only a thousandth, or ten-thousandth of it. While the gene mutation rate is on the order of 10^-11, microsatellites involved in gene expression can evolve much more quickly. Cecal values are a paeodomorphic characteristic, so could change quickly due to gene expression. Natural selection, of course, would sort through the variations concerning cecal values, as well as head shape. PaV: As to ligers and tigons, hybrids of lions and tigers, their infertility shows the limited extent that “hybrid vigor” should be used in pretending to extend microevolution to macrovevolution-size events. Lion-tiger hybrids are sometimes fertile. In any case, as Darwin pointed out, there are gradations of reproductive isolation. That's evidence of a process by which organisms speciate. PaV: Yes, Darwin’s principle of Divergence is about ecological competition. And it involves progeny of the parent species ‘replacing’ the parent species in the changed environment because they are now “more fit”. The principle of divergence is about how a single species diverges to make better use of resources. Instead of a single species of beetle, you have one that is specialized for the top of the rock, and one that is specialized for under the rock. In any case, the nested hierarchy and the fossil succession still strongly supports branching descent. It's clear from the evidence that diverse organisms have diverged from common ancestors. Zachriel

wd400: As to the Adriatic lizards, if you calculate the effective population size, and you consider the numbers present 35 generations later, this is not enough time for the population as a whole to sample the entire genome; probably only a thousandth, or ten-thousandth of it. (IOW, not even ONE needed mutation will likely show up) So why do you give such a seemingly "learned" answer when you know full well that population genetics can't even begin to give an answer. How is this being intellectually honest? As to ligers and tigons, hybrids of lions and tigers, their infertility shows the limited extent that "hybrid vigor" should be used in pretending to extend microevolution to macrovevolution-size events.

Well, it’s only because I can’t map what you are saying to what Darwin said about divergence, which, by the way, is not the basis of our modern understanding of speciation, because, you know, modern evolutionary biology isn’t “Darwinism”. (Darwin’s principle of divergence is about ecological competition between individuals).

Where do I begin? What is the "modern understanding of speciation"? I've read all the words, Mayr, and others, but it's always the same: "a little bit of this, and a little bit of that, shake it around, throw some star dust on it, and viola! macroevolution/speciation." I have yet to find a description of macroevolution that is not just a whole bunch of words and nothing more. I've been looking now for almost twenty years. Show me one that is something more and I might become a convert. Yes, Darwin's principle of Divergence is about ecological competition. And it involves progeny of the parent species 'replacing' the parent species in the changed environment because they are now "more fit". And without that, you will never have macroevolution because, as in the case of dogs and wolves, all the change that takes place within species can always simply "revert," just as in the case of those Darwin's Finches that "fuse" together, and don't replace the original species. And Darwin knew this better than everyone else. Again, devastating results---at least for me, because I was beginning to think that Darwinism had finally been demonstrated to be true. Alas. PaV

PaV, THe problem is the quotes aren't making the point you think they are. Take this one, you bolded a good definition of species unlike the nee you've been defending above.

A single evolutionary lineage of organisms within which genes can be shared, and that maintains its integrity with respect to other lineages through both time and space

That's the one I've been using this whole time, and the one under which the exisitance of viable hyrbrids is not great suprisse (in fact, it's been estimated that as many as 20% of animal species produce such, including tigers and lions on occasion).

I’ve given you enough information. The problem is that population genetics can’t even begin to give an answer. So you dismiss the entire thing.

I don't dimiss it, I think it's not going to give you a satisfactory ground-up answer. To understand the whole think you'd need to know about development in squamates, phenotypic diversity in the parent population, plasticity of the traits at hand, and their heritablity both on and off the island. There would still be a population genetic explanation (mutation, alleles, strengths of selection...), but it would not be the whole picture. (the interdisciplinary nature of modern evolutionary biology is precisely why I think it's fun, btw) N.B. You have still failed to make one comment about the OP. How interesting is that? I've made several. In the last comment I said this "I’ve already responded to the article. It’s nice application of some clever pop. gen., its further confirmation that hybridisation is an important evolution process."

You remain silent about the Principle of Divergence. That, too, is interesting.

Well, it's only because I can't map what you are saying to what Darwin said about divergence, which, by the way, is not the basis of our modern understanding of speciation, because, you know, modern evolutionary biology isn't "Darwinism". (Darwin's principle of divergence is about ecological competition between individuals). wd400

PaV: Population genetics has its purposes; but as an explanation for macroevolution, it doesn’t work. Population genetics just models certain aspects of evolution. It can, however, model gradations of reproductive isolation. Zachriel

wd400: As usual, you simply overlook the quotes I've provided in making my point. Then you say that I have no point to make. Wonderful science, that. You write:

I don’t know a damn thing about the lizards, and I’m not going to try an explain with popgen any more than I’d explain the shape of grand canyon with particle physics.

I've given you enough information. The problem is that population genetics can't even begin to give an answer. So you dismiss the entire thing. At Cornell they say that neo-Darwinism is dead. We just repeat it here. You say: "it's no big deal," and "we've known that for a long time." Population genetics has its purposes; but as an explanation for macroevolution, it doesn't work. And from what I see, it will never work. N.B. You have still failed to make one comment about the OP. How interesting is that? You remain silent about the Principle of Divergence. That, too, is interesting. Happy New Year! PaV

PaV: Darwin’s theory rises and falls on his Principle of Divergence Darwin was aware that hybridization could sometimes increase fertility, while other times lead to reduced sterility. Zachriel

PaV: What was “devastating” about the hybridization is that it put a complete stop to any “divergence” taking place. In two species, but not in others. PaV: Darwin’s theory rises and falls on his Principle of Divergence Yes, and the original finches have diverged. Panmixia of two species will still leave multiple species. PaV: One definition of species that is used is that of not being able to interbreed with another similar species. That’s just out there as a workable model until recently. There may be some gene flow, and a species still able to maintain its distinctive characteristics. PaV: The problem is what I state above: where is the “divergence” that Darwinism hinges upon? Um, there are many species where there used to be just one, different enough that Darwin didn't recognize many of them as being finches. That was determined later from Darwin's specimens by the ornithologist John Gould. - Edited statement concerning panmixa. Zachriel

PaV, I'm sorty, but you are so clueless about the topic which you speak, while being so sure of being right, that it's almost impossible to talk to you. If the hybrid finches converged into a new hybrid of Daphne Major (and that doesn't seem to be the case) you would still have evolutionary divergence. You have a new species evolving of Daphne Major distinct from those on other islands. If you think species are defined by their inablity to produce viable offspring then you are wrong. If you think HWE is a conservative force, or indeed a force at all in biololgy then you are wrong. If you think it obtains when the migration rate between demes is tiny then you are really wrong. If you think a psassage like the one I reproduce below has any substantial meaning then I can't agree with you. I rather suspect that “hybrids,” being somewhat established because of robust environmental conditions will, when conditions are sparing, sparse and tough, undergo a “pulling” apart, likely tied into some epigenetic effect and tied to environmental conditions.

But the only “anti-science” I see at work here comes from you: (1) every time someone is “surprised,” every time something happens that is unexpected, you just wave it away. “Oh, that’s some open-access journal (even though it’s a Nature magazine journal), and these scientists are not considered to do work of high merit.” etc. and (2) “Oh, that’s been known for 30 years.” As if evolutionary biology had dealt with it and resolved the issues 30 years ago, when, in fact, it was only posed as a question. and (3) you’ve still not responded to the findings of the study that “News” cites. Will you wave this off, too? No. People put out dumb press releases and those that find them comforting reproduce the talking points here. Often with hyperbolic statements about the death of Darwinism or even Mendelism. I wouldn't disgard an article because it was in an OA journal, but I don't think the death of mendalism will be presented in a journal designed to catch failed submissions to Nature journals. I've already responded to the article. It's nice application of some clever pop. gen., its further confirmation that hybridisation is an important evolutoin process. I don't know a damn thing about the lizards, and I'm not going to try an explain with popgen any more than I'd explain the shape of grand canyon with particle physics.

wd400

wd400:

Your later comments don’t seem to relate to your earlier ones.

That's because I went back to see why we were talking about my comments and not about the OP. Have you forgotten the OP? Have you forgotten I asked this: Our findings highlight the extent and role of introgression in nature and call for careful analysis and interpretation of house mouse data in evolutionary and genetic studies. You've never answered this question. There are other questions you've failed to answer. You seem to choose the questions you like to answer, and then simply overlook others (why? are they difficult ones?)

Are you going to defend/withdraw any of you ridiculous comments above? That interspecies hybrids are a big unexpected problem?

From Science20:

In their talk yesterday, the Grants argued that this gene flow between two species is leading to more genetic convergence - meaning that these two species could be on their way to forming a new mixed species. This is exactly the opposite of what was happening for the last 2-3 million years: the various finch species of the Galapagos have been diverging from each other since they last shared a common ancestor. 2-3 million years of divergence has been enough to create 14 new finch species, but not enough to eliminate all cross-species mating - that kind of sexual isolation takes much, much longer.

What was "devastating" about the hybridization is that it put a complete stop to any "divergence" taking place. Darwin's theory rises and falls on his Principle of Divergence; without this, NS was already noticed and talked about 30 years before the publication of OOS. You, as a "believing" Darwinist simply hand-wave this problem away. Sorry, I like science; not dogma. As I was reading Weiner's book I thought that finally, at last, here were some great field study data that pointing in the direction of "divergence," or, to call it by a different name, "macroevolution." And then the hybridization. Convergence. Uh oh.

wd400: That species are defined by in ability to hybridize?

Shouldn't you have phrased it, "by an inability to have viable" offspring? Why didn't you? To make your point? If I simply thought that hybridization was impossible, then why in the world would I talk about hybrid vigor? One concept would mutually exclude another? Can't you figure out things like that? Do I need to explain it? Here's Wikipedia to slow you down again:

It is surprisingly difficult to define the word "species" in a way that applies to all naturally occurring organisms,[21] and the debate among biologists about how to define "species" and how to identify actual species is called the species problem. Over two dozen distinct definitions of "species" are in use amongst biologists

One definition of species that is used is that of not being able to interbreed with another similar species. That's just out there as a workable model until recently. But, of course, this is not a problem for you since you "understand" all of this. You "know" what a species is, right? Just like you know the cause of hybrid vigor. Some more:

A single evolutionary lineage of organisms within which genes can be shared, and that maintains its integrity with respect to other lineages through both time and space. At some point in the evolution of such a group, some members may diverge from the main population and evolve into a subspecies, a process that may eventually lead to the formation of a new species if isolation (geographical or ecological) is maintained. The process through which species are formed by evolution is called speciation. A species that gives rise to another species is a paraphyletic species, or paraspecies

Why don't you admit you were wrong in the way you characterized what I had written?

wd400: That the discovery of interogressive hybridization through population genetics is a big problem for population genetics?

Yes, it's a problem. Why? Because now two gene pools have joined, and you're really not sure what you're dealing with. Further, these kinds of hybridizations may have occurred in lots of other lineages and remain unknown to those using popl. gen. equations. This will render their results wrong, though unknowingly. So what's there to retract? You simply are arrogantly triumphant in your view of what population genetics can, and cannot do? So, at this point, I will again ask you:

There were a species of lizards taken to an island in the Adriatic where no lizards existed. It was the start of an experiment. About 25 to 30 lizards were transported, IIRC. Then the Bosnian War set in. When they went to the island after the war, there were about 3 to 400 lizards (IIRC). This was 35 years later. The transported lizards now had a larger jaw, was slightly larger overall, had changed its behavior, and, most markedly, now had cecal valves in its intestinal tract. Please explain how this happened using population genetics.

wd400:

Are you going to tell me what you think HWE is? becuase every time you mention it you seem to be talking about something else? And has it to do with stasis?

You know full well what the HWE is. And if it doesn't have anything to do with "stasis," then why is it called "equilibria"? You want to make a big deal about the assumptions, the caveats, that attach to the HWE; nevertheless, it is, by definition, a conservative force in population genetics. wd400:

I don’t know the point of your post #30 is. I’ve said from the start speciation is often the result of selection pulling lineages/populations apart and and recombination pulling them together. In the case of the Daphne Major finches the net effect over many generations has been the maintenance of separate trajectories. In other cases you do end up with hrbrid swarms, but if that happened on Daphne major you’d end up with a new hybrid species distinct fom other islands’s ground finches (presuming migration between islands was v. minimal). So, where’s the problem?

The problem is what I state above: where is the "divergence" that Darwinism hinges upon? I rather suspect that "hybrids," being somewhat established because of robust environmental conditions will, when conditions are sparing, sparse and tough, undergo a "pulling" apart, likely tied into some epigenetic effect and tied to environmental conditions. Now this is my take on it. But, unless you have genetic and field study facts to dispute it, I'm not going to simply accept your view on the matter. You've state elsewhere that your interest in coming to UD is to see "anti-science" comes into being. But the only "anti-science" I see at work here comes from you: (1) every time someone is "surprised," every time something happens that is unexpected, you just wave it away. "Oh, that's some open-access journal (even though it's a Nature magazine journal), and these scientists are not considered to do work of high merit." etc. and (2) "Oh, that's been known for 30 years." As if evolutionary biology had dealt with it and resolved the issues 30 years ago, when, in fact, it was only posed as a question. and (3) you've still not responded to the findings of the study that "News" cites. Will you wave this off, too? I'm not responding to any more of your posts until such time as you give some kind of response to the Adriatic island lizard scenario. PaV

PaV: If this “principle” of his were to be found to continue on, always bringing about more and more divergence, then you have the groundwork for Darwin’s “Law of Divergence.” Darwin's Law of Divergence refers to an ecological effect due to specialization. PaV: But nature doesn’t work that way. There is ample evidence that close inbreeding is detrimental to a line. PaV: After two (or more?) very rainy seasons, the hybidization took place. There was enough food for everyone. The hybrids simply were the more fertile species; an instance, I suppose, of ‘hybrid vigor.’ It was the genetic variability due to hybridization that was advantageous, which can then lead to new species (The Grants observed a new mating population due to hybridization), or the panmixia of previously separate species (which the Grants did not observe). PaV: IOW, you effectively have stasis, just as in the case of HWE where gene frequencies change, but the total number of “alleles” remain the same. No, you have countervailing forces leading to chaotic results. There is no reasonable doubt that Darwin's Finches are related by common descent, then diverged. They mostly don't interbreed, but when they do, it can change the course of their evolution. PaV: you have one force at work that wants to go “left,” and another that wants to “right,” and, over time, you’ll average out to continuing in the same direction. More typically, you'll have chaos. And that is what the Grants observed. https://www.youtube.com/watch?v=U39RMUzCjiU Zachriel

Are you going to defend/withdraw any of you ridiculous comments above? That interspecies hybrids are a big unexpected problem? That species are defined by in ability to hybridize? That the discovery of interogressive hybridization through population genetics is a big problem for population genetics? Are you going to tell me what you think HWE is? becuase every time you mention it you seem to be talking about something else? And has it to do with stasis? I don't know the point of your post #30 is. I've said from the start speciation is often the result of selection pulling lineages/populations apart and and recombination pulling them together. In the case of the Daphne Major finches the net effect over many generations has been the maintenance of separate trajectories. In other cases you do end up with hrbrid swarms, but if that happened on Daphne major you'd end up with a new hybrid species distinct fom other islands's ground finches (presuming migration between islands was v. minimal). So, where's the problem? wd400

p.206 The Beak of the Finch:

Roughly one out of ten of the finches born on the desert islet of Daphne Major now are hybrids, and the hybrids are doing better than any of the others on the island. In a blink of evolutionary time, all of Darwin's finches could run together and congeal, and the sculptor's art would be lost. As the evolutionist Ernst Mayr once pointed out, the tendency toward fusion, the "Successful leakage of genes from one species into another," is " a self-accelerating process." Each case of introgression weakens the invisible barriers between two species and leads o increased frequency of hybridization, a process that if unchecked will spill downhill faster and faster, "until ultimately the two species are connected by a contiunuous hbyrid swarm."

Exactly the point I was making. You will point out the role of the "sculptor," i.e., NS. But my point was really that you have one force working against another: IOW, you effectively have stasis, just as in the case of HWE where gene frequencies change, but the total number of "alleles" remain the same. Let's put it another way: you have one force at work that wants to go "left," and another that wants to "right," and, over time, you'll average out to continuing in the same direction. You still haven't addressed the OP. PaV

What "dominance" effects? The ones you "see" there?. The ones you "define" as being there? PaV

There were a species of lizards taken to an island in the Adriatic where no lizards existed. It was the start of an experiment. About 25 to 30 lizards were transported, IIRC. Then the Bosnian War set in. When they went to the island after the war, there were about 3 to 400 lizards (IIRC). This was 35 years later. The transported lizards now had a larger jaw, was slightly larger overall, had changed its behavior, and, most markedly, now had cecal valves in its intestinal tract. Please explain how this happened using population genetics. PaV

Finally, I'm interested in where you think the explanation in the passage you quoted in 22 is? And did you note in requires there to be dominance effects for the different miRNA alleles? Which you think don't exist (or something)? wd400

This remark referred to Weiner’s book and the on-going study taking place on Daphne Major. These were supposed to be distinct species, and, so, should not have interbred Why? There are many examples of inter-specific hybrids. Are loins and tigers one species? This “mixing” of ‘gene pools’ meant that all the divergence they saw, and the correlation between environment and species divergence they had so rigourously followed, led nowhere No. Isn’t this just another ‘monkey-wrench’ thrown into the mathematical gears of population genetics? What? They could only detect this hybridisation due to pop. gen. wd400

PaV:

No one saw it coming. And it had devastating effects.

This remark referred to Weiner's book and the on-going study taking place on Daphne Major. These were supposed to be distinct species, and, so, should not have interbred. Hence, "no one saw it coming." "And it had devastating effects." Yes, it did. Because the model the Grants were employing didn't include this possibility. This "mixing" of 'gene pools' meant that all the divergence they saw, and the correlation between environment and species divergence they had so rigourously followed, led nowhere. Hence the very sedate tone of the second half of the book. Now, wd400, I wasn't asking you what you thought about Weiner's book, nor my interpretation. I was asking you what you thought about the study being reported. They say, for example:

Our findings highlight the extent and role of introgression in nature and call for careful analysis and interpretation of house mouse data in evolutionary and genetic studies.

Isn't this just another 'monkey-wrench' thrown into the mathematical gears of population genetics? You know: another day, another bad day for Darwinism. And, BTW, you know it's not the IDers who are saying this, but evolutionary biologists at Cornell: "Neo-Dawinism is dead." But what do your colleagues know? Right? PaV

You are coming unraveled at this point PaV. Your later comments don't seem to relate to your earlier ones. And the new stuff is... really something. The idea that 'allele' or dominance don't meant anything in after molecular biology is just... bizarre. Quite what I'm meant to make of your half-remembered example of some kind of birdish-reptile thing I dont' know. But from what little I I cam make of it you've forgotten the most basic understanding of neutral theory. I really don't know what you think HWE is. If most mutations are deleterious then populations will be out of HWE, with fewer homozogotes than expected. Oh, and species aren't defined but their inability to interbreed, or tigers and lions would be the same species (and there'd be about 10 species of flowering plants...). So. Again, I really think you should learn some biology before you make these leaps to comfortable conclusions. wd400

Zachriel:

Not sure why you would say that. It’s certainly not supported by your quote from “Origin of Species”.

From my quote of Darwin: I have collected so large a body of facts, showing that close interbreeding lessens fertility, . . . Darwin thinks that breeding between organisms that are "close" tends to wither, while, conversely, those that are "dissimilar" tend to be very fertile. If this "principle" of his were to be found to continue on, always bringing about more and more divergence, then you have the groundwork for Darwin's "Law of Divergence." But nature doesn't work that way. Or does it? Do you have an example?

The Grants found the hybridization in Darwin’s finches was most successful when intermediate beak forms were advantageous, but less successful otherwise.

That's not what I read in Weiner's book. After two (or more?) very rainy seasons, the hybidization took place. There was enough food for everyone. The hybrids simply were the more fertile species; an instance, I suppose, of 'hybrid vigor.' But the point I'm making here is that this moves in the opposite direction of "divergence." PaV

This sounds like an "explanation": From Wikipedia:

An epigenetic contribution to heterosis has been established in plants, and it has also been reported in animals. MicroRNAs (miRNAs), discovered in 1993, are a class of non-coding small RNAs which repress the translation of messenger RNAs (mRNAs) or cause degradation of mRNAs. In hybrid plants, most miRNAs have non-additive expression (it might be higher or lower than the levels in the parents). This suggests that the small RNAs are involved in the growth, vigor and adaptation of hybrids.

It gives very specific details, and they make sense. PaV

As to hybridization, the two species they were tracking on Daphne Major were considered distinct species, and, by definition, could not interbreed. But they did. That was the reason I said that it "wasn't supposed to happen." Not hybridization, but among two "species." But, of course, is typical post hoc fashion, we now "know" that they were "varieties," or at least one of them was. PaV

When you quoted Darwin in #9 you seem to have completely blown over his statement about hybrid vigour “that an occasional cross with a distinct individual or a variety increases fertility”

But, of course, that's what hybrid vigour is. Why would I need to "define" it?

I guess you then turned to wiki and decided the existence of two explanations for hybrid vigour meant the phenomenon was not well understood.

I turned to Wikipedia to point out that you were wrong. Only in your mind is there an "understanding" of the phenomenon. Earlier, you gave this explanation:

Some or all of the fitness lost by those deleterious alleles that are not completely dominant will be regained in the hets, and so you get off spring that outdo either parent.

First: If I say that every object I release from my hand will fall to the earth, this statement doesn't "explain" gravity. It doesn't mean I understand general relativity. We KNOW that hybrid vigour occurs. I never disputed that. Right? But how long will hybrid vigor continue? Don't they have to keep "crossing" wheat grain? Why? Why don't we have a better, more "fit", wheat grain by now that perseveres as a species all on its own? The persistence of this effect is what Darwin relied upon, and we know that the effect diminishes with successive breeding. I could be wrong here; if so, then please clarify this. Second: Look at this so-called "understanding." What is an "allele"? This is a term that comes from a time well before molecular biology. What is "fitness"? What is "dominance"? Yes, these are definitions we can all look up on Wikipedia; but these definitions themselves are ill-defined. No one really talks about "dominance" anymore do they? And the definition you give demonstrating that you "understand" hybrid vigor demonstrates nothing like that at all. It's simply a definition that sounds learned but is really empty of content. Here's where you and I part company. You really believe this is an "explanation" and that you really "understand" hybrid vigor. OTOH, I say that we only KNOW that hybrid vigor occurs, and that when it comes to the actual mechanism involved, that no one really knows---we simply get some 'hand-waving' Darwinist explanation that satisfies Darwinists so that they tell us: "Just keep moving on. There's no problem here." My "hunch" is that we're dealing with epigenetic affects, which is now given as possible source of explanation. But if I say that it likely has something to do with 'epigenetics,' that in no way means I've 'explained' it. As to HWE, you say that mutations won't allow you to remain at the same HWE. But aren't most mutation deleterious? Doesn't NS remmove deleterious mutations? Isn't NS ordered to maintaining HWE in this respect? There was a study out a couple of years back. This is all from memory. But they studied, IIRC, the genetic variability amongst a species of reptiles/birds (can't remember) that had been isolated upon some high terrain from apparently millions upon millions of years. And the variability was low. IOW, if there were any "mutations," NS got rid of them somewhere along the line. As Gould has noted, we see "stasis" for the most part. Given enough time, I think we'd see different "species" "evolve," which, given enough time, would disappear, followed by other "species," and which after a long period of time, would revert back to the original "species." Unless, of course, the environment changed. My remarks about HWE were deeply influenced by the fact that at Daphne Major the environment is both isolated and relatively unchanging (geographically, not weather wise). What I'm trying to get at here is that macroevolution has to fight the forces of stasis---which are considerable. Don't we find "living fossils," for example? PaV

I’m not “digging” at all; instead, I’m “pointing out.”

With each post you embarrass yourself further, I think what you are doing is digging. For instance, you have a bad habit of reading only the parts of references that you think support your view. When you quoted Darwin in #9 you seem to have completely blown over his statement about hybrid vigour "that an occasional cross with a distinct individual or a variety increases fertility" I guess you then turned to wiki and decided the existence of two explanations for hybrid vigour meant the phenomenon was not well understood. But as your own quoted passage says, the two explanations are not mutually exclusive. There is seldom a single explanation to anything in biology, and this is another case. It's quite possible for a phenomenom to have multiple explanations and be well understood, and hybrid vigour is one such. Moreover, we are taking about birds, where trans-generational epigenetics is not known to exist, so it's a bit of stretch to think it matters in this case.

What I wrote had reference to what happened on Daphne Major, and recorded in “The Beak of a Finch.” So, let’s not bring in general results.

I'm talking about G. fortis and G. scandens on Daphne Major. They just aren't pooled to one species.

No one is disputing this. However, what will this look like in the long run: a hundred years; two hundred years? That is what matters.

Sure, and ~1% hybridasation with some fitness cost for hybrids is just not enough to collapse these species.

Again, everything is in reference to Daphne Major. There were NO “occasional migrants.” So there’s nothing to mix.

I mean migrants between demes (here meaning the species), so the hybrids are the occasional migrants. A few percent of breeding birds in some years will not make the populations approach HWE. It should be obvious the species' populations are not panmictic and so don't meet the assumptions of HWE. I am also curious as to what you think HWE is? It doesn't imply stasis, unless you ignore mutation. But you can't do that, so, again, what do you think HWE is? wd400

At some point you are going to want to stop digging. I'm not "digging" at all; instead, I'm "pointing out." wd400:

There aren’t “opposing” explanations of hybrid vigour, there is one well established one (which I described) and a less important one (epigenetics, which can only relate to lineages in which trans-generational epigenetics is a major force, like plants and unlike birds). They aren’t mutually exclusive.

From the Wikipedia:

Since the early 1900s (as discussed in the article Dominance versus overdominance) two competing genetic hypotheses, not necessarily mutually exclusive, have been developed to explain hybrid vigor. More recently, an epigenetic component of hybrid vigor has also been established.[4][5]

wd400: Hyrbrid vigor is well understood.It arises when you cross inbred lineages, as the F1 produces many heterozygotes for the loci fixed for deleterious alleles in one parent. So, hybrid vigor is "well understood," and yet, there are "two competing genetic hypotheses" since the 1900's. Shouldn't that have been enough time to settle the issue? Why are they still "competing" if everything is so "well understood." To me, this is nothing more than Darwinian "hand-waving." PaV:

There are two opposing views as to how hybrid vigor comes about. Thank you for giving one of them

Which of the two of us was more 'on the mark'? I know my answer. wd400:

It is just not true that that hyrbridization in Darwin’s finches has “pooled” two species to one.

PaV:

If you read Weiner’s “The Beak of the Finch,” . . . .

What I wrote had reference to what happened on Daphne Major, and recorded in "The Beak of a Finch." So, let's not bring in general results. Have you read the book?

That they’ve maintained their distinct evolutionary trajectories in the face of hybridization is in fact evidence of the importance of selection in maintaining species boundaries.

No one is disputing this. However, what will this look like in the long run: a hundred years; two hundred years? That is what matters. Not the short run. (I think some kind of NGE is going on here, but I'm not going to spell it out for anyone. They'll have to discover it themselves.)

Finally, it’s bizzare to imagine populations trading occasional migrants will approach H.W.E. Literally the first thing you learn about H.W.E are its assumptions, which include panmixia and the absence of selection.

Again, everything is in reference to Daphne Major. There were NO "occasional migrants." So there's nothing to mix. PaV

At some point you are going to want to stop digging. There aren't "opposing" explanations of hybrid vigour, there is one well established one (which I described) and a less important one (epigenetics, which can only relate to lineages in which trans-generational epigenetics is a major force, like plants and unlike birds). They aren't mutually exclusive. It is just not true that that hyrbridization in Darwin's finches has "pooled" two species to one. That they've maintained their distinct evolutionary trajectories in the face of hybridisation is in factt evidence of the importance of selection in maintaining speies boundaries. Finally, it's bizzare to imagine populations trading occasional migrants will approach H.W.E. Literally the first thing you learn about H.W.E are its assumptions, which include panmixia and the absence of selection. wd400

The "Random Genetic Drift" Fallacy Mung

wd400: It’s as if you are going out of your way to demonstrate both your over-confidence and your ignorance. Isn't this the pot calling the kettle black? There are two opposing views as to how hybrid vigor comes about. Thank you for giving one of them. The rest of the answer is bluster. These species were thought not to interbreed. But they did. An honest answer might acknowledge that with hybridization, what were thought to be two well-defined species have now pooled what once was considered separate. If this continues, if this hybridization, followed by "speciation" (i.e., stratification of beak size given environmental conditions), and then hybridization, effectively, the Hardy-Weinberg Equilibria then applies to the population. So where is "evolution"? You have stasis. From a population genetics point of view, I don't see what value any analysis of the population will give you. It comes down to guesswork...............with very "precise" answers. PaV

So recombination can act as a throttle on selection? If recombination is successful will it defeat

Recombination can prevent divergent selection from pulling two lineages apart and producing new species (something Darwin didn't really get). So, recombination doesn't "defeat" selection generally, but it can prevent selection from creating new species. There is a very rich literature on this.

If hybridization is more common that we thought does that mean that selection is less successful/important than we thought?

No. In fact, one could argue that if hybridization is more common than we thought then selection must more important. For species to remain distinct even in the face of lots of hybridization, selection must be acting to keep each lineage different. wd400

wd400 says, We have two opposing forces, selection (for the most part) is driving the lineages apart and recombination (via hybridization) is bringing them together. quick questions...... So recombination can act as a throttle on selection? If recombination is successful will it defeat selection? If hybridization is more common that we thought does that mean that selection is less successful/important than we thought? peace peace fifthmonarchyman

PAV, What do you believe the finch should have died out from, according to Darwin? Its increased fertility? goodusername

It's as if you are going out of your way to demonstrate both your over-confidence and your ignorance. Hyrbrid vigor is well understood.It arises when you cross inbred lineages, as the F1 produces many heterozygotes for the loci fixed for deleterious alleles in one parent. Some or all of the fitness lost by those deleterious alleles that are not completely dominant will be regained in the hets, and so you get off spring that outdo either parent. Rather than being a reason to pack up and start again, hybridization among Galapagos finches is nice example of how hybridisatoin works within population genetics. We have two opposing forces, selection (for the most part) is driving the lineages apart and recombination (via hybridization) is bringing them together. That these lineages maintain distinct morphologies, songs and niches in the face of the potential homogenising effects of hybridisation is good evidence that they are indeed good species. wd400

PaV: Per Darwin, the hybrid finch on Daphne Major should have died out. Not sure why you would say that. It's certainly not supported by your quote from "Origin of Species". Darwin states that the hybridization can occasionally increase fertility. The Grants found the hybridization in Darwin's finches was most successful when intermediate beak forms were advantageous, but less successful otherwise. PaV: And it is based on this reasoning of Darwin that he concludes that varieties are ‘incipient species.’ They are not incipient, but distinct species. Zachriel

Charles Darwin: OOS: "Nevertheless I believe that in all these experiments the fertility has been diminshed by an independent cause, namely, from close interbreeding. I have collected so large a body of facts, showing that close interbreeding lessens fertility, and, on the other hand, that an occasional cross with a distinct individual or a variety increases fertility, that I cannot doubt the correctness of this almost universal belief amongst breeders." Per Darwin, the hybrid finch on Daphne Major should have died out. But it didn't. It took over. And it is based on this reasoning of Darwin that he concludes that varieties are 'incipient species.' But he was wrong about his own finches! And, he didn't fully understand the concept of hybrid vigor, for which, till this day, no acceptable explanation has been given. PaV

It's become increasingly clear in recent years that hybridization between animal species is relatively common, and an important evolutionary force. Hell, there's evidence of this in humans, an important adaptation to high-altitude got into the Tibetan population by way of another human species What I find boring if they way you think any finding that increases our knowledge of biology requires the scrapping of everything we already knew. We can uses genetics and genomics to detect hybridsation, we can model it very easily (it's just migration between populations, after all), and in turn built statistical measures that let us infer the demographic and selective history of alleles given hybridization. This "oh, but the researchers were suprised" shtick is equally boring. Suprising results are the ones that get published and get press releases written about them (and press officers will always try an emphasize the novelty of their researcher's work). That this mouse lineage has this history is a little suprising, but it adds to a long list of examples of hybridsation in animals so it's not generally uprising that hybridization is an important evolutionary force. wd400

wd400: Unlike you, I'm intuitive. Unlike you, I don't have a career to protect. Taken together, when I see problems for Darwinian theory, I pay attention; you simply sweep them under the rug.

Nakhleh said other studies may have missed evidence of hybridization because the researchers weren’t specifically looking for it.

Could this possibly be because it didn't fit into their models of evolution? Does this apply to you?

While introgressive hybridization is thought to be common among plants, the finding suggests that hybridization in mammals may not be the evolutionary dead end biologists once commonly thought.

Your comments seem to suggest that if I knew more biology, then I wouldn't be surprised by this. Why are they surprised? Why aren't you? Compare your answer to that of Zachriel. Specifically, address this issue: how do you deal with the possibility of "hybridization" in your population genetics models? PaV

vh: nothing is a theoretical problem for evolutionary theory It would be hard to argue hybridization is a theoretical problem as Darwin pointed to hybridization as evidence in support of his theory. Zachriel

No one saw it coming. And it had devastating effects. I wonder what wd400 thnks of this. Just the normal -- PaV knows very nearly nothing about biology but takes any slightly interesting result to mean the end of evolutionary biology. Boring. wd400

Pav, nothing is a theoretical problem for evolutionary theory. Everything can be incorporated. vh

What we see in most research reports are descriptions of the current mechanisms, though still missing many details. Any known documentation containing a detailed description of hypothetical processes leading to setup the mechanisms that operate within the cells in all scenarios? Dionisio

PaV: “hybridization”!!! That’s not supposed to happen. Actually, hybridization is much more common in birds than mammals. Nor is hybridization a theoretical problem for evolutionary theory. Indeed, it's important evidence in "Origin of Species". Zachriel

If you read Weiner's "The Beak of the Finch," you'll find that the first half reads like the perfect illustration of Darwinism and neo-Darwinism. Fascinating and substantial stuff. But the second half reads like someone has lost their way. Nothing seems to add up; Darwinian expectations aren't turning up in the results; and the ultimate result of the experiment in time ends with: ............... "hybridization"!!! That's not supposed to happen. And hybridization means you almost have to throw out all of the results, the great results, previously measured on the Galapagos Island where they were recorded. No one saw it coming. And it had devastating effects. I wonder what wd400 thnks of this. PaV