Galapagos finches

I've been reading Milton, and some of what he says about the finches makes sense to me. Wanted to run that by y'all.He says that the finches fluctuate in beak size over wet and dry seasons, with little net change. That they interbreed, producing vigorous offspring. And that division into thirteen species may be wishful thinking.Now I am not questioning that they demonstrate natural selection in action. I am questioning speciation here. It seems to me that when the definition of speciation in higher animals was diluted from Dobzhansky's original spec (cannot physiologically interbreed with other groups) then the door was opened for cheating.Can it be argued that the Galapagos finch is one species with regional variations, and that it shows nothing whatsoever about macroevolution?I mean, humans vary far more than the finches, and we are still one species....

Wells says:Writing in Science in 1992, the Grants [finch researchers of good and long repute living on the islands] noted that the superior fitness of hybrids among populations of Darwin's finches "calls into question their designation as species." The following year, Peter Grant acknowledged that if species were strictly defined by inability to interbreed then "we would recognize only two species of Darwin's finch on Daphne," instead of the usual four. "The three populations of ground finches on Genovesa would similarly reduced to one species." Grant continued. "At the extreme, six species would be recognized in place of the current 14, and additional study might necessitate yet further reduction."Peter R Grant and B. Rosemary Grant, "Speciation and hybridization in island birds", Phil. Trans. of the Royal Soc. of London B 351 (1996), pp765-772.Also, P Grant, Ecology and Evolution of Darwin's Finches, p206.Also, Grants' article in Endless Forms (Howard and Berlocher eds 1998), pp 404-422.

The above linked article says: But wait a minute. Are species defined "strictly by inability to interbreed"? Not by any species concept commonly used today. The Biological Species concept as described by Mayr emphasizes reproductive isolation rather than lack of interfertility. The key to the concept is barriers to gene exchange, which can include infertility, but are not restricted to it by any means. Discussions of prezygotic reproductive barriers can be found in any decent textbook. Wells knows this. He also knows that reproductive isolation in the finches on the Galapagos is primarily of the prezygotic type, because his sources by the Grants emphasize it over and over. So, Wells has no real point here. However, the general public not familiar with species concepts as used by biologists might consider his arguments authoritative. Well, no, not so fast. Species was defined by Dobzhansky as based on the physiological inability to interbreed, originally. This concept has been moved away from, the literature says, because it creates problems in plants and asexual organisms. It is also impossible to apply to fossils. However, when it comes to higher animals of the still existing category, it has the advantage of preventing wishful thinking of the kind that may well have happened with the finches, where we have a bunch of birds that are almost identical, with some differences in beaks, songs, and the food they eat, among whom preferences for mating with their own in-group has been noted, but has not been exclusive. If this kind of thinking were to be applied to humans, the Chassids would be a separate species!The concept of a species is not a clean one and never will be. However, since the key issue about the theory of evolution is accounting for how one organism can evolve into another PROFOUNDLY DIFFERENT organism, I think biology should be careful about not trivializing the concept of species.For more info on speciation: Observed Instances of SpeciationYes, six is more than one, but please note Grant thinks that further reduction could well come with further reevaluation.[This message has been edited by Tamara, 02-08-2004][This message has been edited by Tamara, 02-08-2004]

An interesting perspective on the species issue could come from Dawkins' formula which calls a species a group that has the same number of chromosomes as well as the same number of nucleotides on each. I have read that the finches all have the same number of chromosomes but have not seen any info on the nucleotides. Anyone?Re trivializing, Paul, see my argument ad absurdum (Chassids, above). People should not be calling any group a species just because it has a few different characteristics. Btw, I just heard that wolves, coyotes and dogs have been combined into one species, Canis lupus, with appropriate subspecies. About time! Jackals, however, still roam at large as a separate species.

True. But unless we come up with something that works for birds in such a way that wishful thinking does not play a major role, the Galapages finches remain an illustration for natural selection or even adaptive radiation. But as an illustration of speciation they are not credible, IMO.A quote from the Beak of the Finch: "You can't distinguish these three species by their plumage and usually not by their build or body size either. You have to tell them apart by their beaks. In the jargon of taxonomy, the sullen art of classification, the beak of the ground finch is diagnostic: it is the bird's chief taxonomic character. But because the finches and their beaks are so variable, many of them "are so intermediate in appearance that they cannot safely be identified-a truly remarkable state of affairs. . . ."

Trixie, thanks for the feedback. I guess Dawkins's suggestion does not make sense after all...

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And it is hardly the only example we have.

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That's a good thing, then, because this one is skating on thin ice. Maybe we should ask the Grants what they think about this...You talk about evidence, Paul. I have been looking for evidence that the historical classification is on solid footing. I have not found it. So far. If anyone here has it, I'll be happy to look at it.[This message has been edited by Tamara, 02-08-2004]

Paul, please note again what Peter Grant is saying. AT THE EXTREME, he stresses, there would be 6 species in his view. That means that he thinks most likely there would be fewer.How many species really are there? Well, it looks to me like most likely, 5 or fewer. Possibly even one, although the Grants are not about to say that in public (if indeed this is entertained by them) because in today's climate, they would be accused of aiding the enemy. So it would be interesting to know what they privately think.Is it reasonable to trust the speciation claim? Given the evidence of a grossly exagerated species list, I say the trustworthiness of the claim is seriously undermined. I am also judging the current criteria for a species of these finches as highly unreasonable, in comparison, say, with humans or dogs. For example, the claim has been made that if the drought persisted in the islands, a new species of finch could come about in about 200 years (the drought favors birds with bigger beaks to crack the tougher seeds with). Based on beak size/shape alone??!! Come on... If we bred dogs with pug snouts in many generations, would they be a new species of dog? Oh wait, we already have, and last time I checked, they were still the same old dogs.I am not here to convince anyone. I am here to make up my mind. And so far, this is my best estimation of the matter.[This message has been edited by Tamara, 02-09-2004]

MrH: Clearly, not only creationists but taxonomists and assorted naturalists have also struggled with what a species is, and many have rued the lack of a solid definition.

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The Galapagos finches are fascinating for the fact that they show how a formerly unified population has exploited separate niches and developed structures and instincts best suited to their individual environments.

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Could not agree more.

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The effect of geographical distribution on the rate of speciation is dramatic and persuasive to any rational observer. Unfortunately, creationists have a vested interest in denying that speciation events take place, and for that reason only, they can't consider the finches separate species.

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Dontcha love it when people start the "any rational observer" would realize that... Cut the BS, please! I cannot speak for others, but myself, I have no vested interest in denying that speciation with the finches takes place. I recently found out I was lied to about embryo pictures and the recapitulation thing, and so I decided to find out what else is fishy in the world of darwinism.

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Creationists never tire of telling us that the Galapagos finches tell us nothing about the mechanisms of evolution, that this isn't Darwinian evolution at all, and that we should ignore the clear lessons these birds teach us about the development of life on Earth.

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Did you ever read Wells and Milton? Both agree that this example is a clean and persuasive evidence for natural selection.

MrH, you make a lot of unwarranted assumption about my point of view. I am not against evolution, or science. I am against bullshit. (Guess what -- I just picked up a youth book on evolution put out in 1990, otherwise not bad, which says that human embryos go thru a few days when they have gills. Not gill slits, GILLS! Shows ya... bullshit never dies.)

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We see the changes wrought by natural selection, and we see the vast amount of change in organisms over time. Why shouldn't one type of change be the basis for the other?

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Those that want to make that argument should make a better one than with the finches. If they don't they will lose credibility among us layfolks. As is already happening.

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I'm pretty confident that in the wild, not bred by men, most breeds of dogs--if they were isolated and breeding only among themselves--would be regarded as separate species.

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Temp, yes, ah, if only. Problem is, the finches are not isolated and breeding only among themselves. And even if all toy poodles were dispatched to a desert island (I can dream, no? where they could only breed among themselves because no corgis were available, that still would not make them a separate species, don't you think? The Galapagos Islands are now densely populated in some places. Like the rock doves, house sparrows, and starlings of Eurasia and North America, they have adjusted to human habitation. They are learning to eat scraps and seeds from people. The various types of finches which before were distinguished by differences in bills are becoming "a hybrid swarm" in towns. So perhaps that means that if the finches are not one species now, soon they will be... Problem with your argument is... if chihuahuas and St. Bernards would not be considered one species "in the wild" then why should Icelanders and Bantus be considered one species? You see that sort of thinking opens up a can of worms. Better leave them all together if they interbreed...

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I don't see where you've established this in any way, since even your sources don't say this. Only you say this. "Grossly" exaggerated?

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Yeah, well, if 14 bogus species that should be really six or possibly fewer in the words of THE expert does not strike you as gross exageration, what can I say? I guess my gullibility meter is more finely calibrated than yours!

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This means the next person could legitimately come along, examine the matter further, and assign more species based not just on their further research, but even on their possibly different definition of species.

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I know, exactly. And the rest of us are equally free to jeer from the bleachers.Since there is no chance whatsoever in my opinion that the finches will be objectively reevaluated in the near future (given the cultural climate and their iconic status), I am not holding my breath, and have to decide without having the benefit of those future taxonomical studies.

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I apologize that evolution from Cambrian forms to modern ones is too slow to demonstrate in a lab, but too fast to be captured perfectly in the fossil record. If this seems like rationalization to you, so be it.

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Achtung: Unwarranted assumption about my point of view.

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Your healthy skepticism goes out the window when Wells and Milton are doing the talking.

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Leave them out of it. I am here because I want to hear what others like yourselves have to say. (But when I double-checked on the gill slits et al, and found they have something to say, I started to listen. Maybe you should too.)

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You seem to realize that 'species' will never have a precise definition, but you don't seem to understand our explanations of why this is necessarily so. If you think of a better definition, you may win a Nobel prize.

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Dobzhansky already took care of that one! Then got talked out of it. But it's still there for those who want to tighten up the game.

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You seem to realize why the finches are such an important demostration of adaptive radiation, but you'd rather put that together with the genetic links we recognize between ostensibly unrelated organisms. In other words, the fingerprints of evolution are everywhere but you want us to believe evolution isn't.

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Achtung: More unwarranted assumptions about my point of view.MrH: I don't demand to see anything. I am evaluating.

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The physical (as opposed to geographical) barrier to interbreeding of chihuahuas and St Bernards is a tad higher than that between any two populations of humans, don't you think?

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And yet, they would manage if they had no one else to hump. Those resourceful dogs...!

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BTW, you do know that we have seen speciation in real time in organisms that reproduce rapidly enough for us to see it, right?

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Well, that is what I want to look into next. Any links would be appreciated. I hope the evidence can speak for itself without positing flimsy arguments on the order of poodle species. I would figure that by now, there are new Drosophila species induced in the lab?The other question I have... isn't it true that in order to have something novel (like a novel species or genus) you'd need mutation, right? I mean, selecting for stuff that is already in the gene pool runs into a dead end, no?

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Then the problem of viability of a Bernard pup in a chihuahua mother would arise.

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So what happens when very different sizes of critters do breed (say by insemination)? Would not nature make adjustments for the discrepancy so that the mother does not just blow up?!

Paul, at one time, I read, there were said to be some thirty finch species there. The ornithologist who came up with them said that he could have just made them one species. Once there were I hear 64 species of brown bear, now there is one. I think if you want credibility with us, you gotta come up with something better than a vague definition up for grabs by the splitters.

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Oh and what DOES Wells have to say about "gill slits" ? The structure is there in vertebrate embryos, and it is genuine evidence of evolution even though Wells doesn't like it.

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Are you baiting me or something? There are pharyngeal pouches that develop into neck and jaw and adenoids etc in humans. There are no gills and there are no gill slits. The pharyngeal pouches of humans have nothing whatsoever to do with gills. Since I know from personal experience that the notion of gill slits creates powerful images of human embryos have gills, therefore it must be true we were once fishlike. In other words, it is a propaganda item, and I think it’s high time we all started using the proper term. (And no, I am not denying that there are similarities among various critters in embryonic stage.)As for my bias what would I possibly have to gain by claiming to bias-free? Are you?

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Are tigers and lions now the same species?

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NosyNed, why not? What objection do you have to making them merely a separate subspecies?
Wolves and dogs are now, you knowTemp:

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The only reason I see that dogs are all one species is because we bred them. In the wild, I can't see any way they'd not be separate species. Maybe someone can name for me a species that varies in size and appearance as much as dogs do, yet are all considered one species (rather than one genus).

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Easy. Humans. And we haven’t bred them. (And please note: dogs and wolves are now the same species, and we have not bred them [wolves] either.)I agree it’s a can of worms. But as I said, greater rigor would be in the interest of better argumentation.Re insemination — I was trying to bypass the whole can a st bernard impregnate a chihuahua. I still think it can at least a big male to a small female. Anyway, a side issue.

Temp, please note that the species of finches have not been reduced to 6. As far as I know, there are still officially 14, at this time.As for whether Grant meant at least 6 or at most 6, I admit the quote is ambiguous.[This message has been edited by Tamara, 02-09-2004]