Butterflies: teams and fallacies
Jul 24th 2005Wallabynerd alert
It’s always nice when the much-needed proof of evolution turns out to be both beautiful and so simple that even a chemist can understand it.
In this particular case, it seems that there’s a species of butterfly, or rather two closely-related species, that live near each other. They look a lot alike (even to each other, it turns out), but if they mate with each other, the offspring are less viable (”weedy”, as the BBC put it). So, the butterflies of these two species (but not of other Agrodiaetus species) have a stripe on their wings — one color for each species — so they can tell at a glance who’s who, and avoid mating with the wrong butterfly. (High school biologists speculate that a similar mechanism is responsible for the reproductive isolation of the chess club and the cheerleaders.)
All this, of course, is clearly proof that traits develop by natural selection:
* These butterflies do have this trait;
* Other, similar butterflies do not;
* This trait provides an advantage in this particular case, both now and (likely) in any intermediate forms as it developed;
* Therefore this trait must have developed as these two species diffentiated (evolved) from a common ancestral butterfly.
I don’t have access to *Nature* at home, where this work was published (err, *Nature*, not my house), so perhaps the BBC article didn’t do it justice. I wonder, though –
* How are we so sure that this is a trait that developed? Is there any evidence of butterflies from hundreds of generations back that show this trait partly developed — maybe just a dotted line instead of a solid stripe?
* Is it really essential that these two species of butterfly *both* have a “team stripe”? It would seem to provide practically the same advantage if only of these two species had a stripe — the striped butterflies would only chase the others with stripes, the ones without would leave them alone.
* Do the butterflies really show a preference for their same-striped kin? Or could a Red-Striped B. have a wild fling with a Blue-Striped, though she knows it’s foolish and that one day he’ll return to his own people and leave her desolate and ashamed, struggling to bring up a large family of Purple-Spotted butterflies?
* Finally — is there anything about this that can’t be explained just as easily in terms of design? Oh, wait, that’d mean being open to an alternative hypothesis, and that’s just not scientific.
(Please note — Ed Darrell and anyone else who wants to defend the sacred bastion of evolution — I’m simply pointing this out as an example of biology jumping from “if this evolved, then it would have provided an advantage” to “therefore it evolved”, which is about as “scientific” as a prosecutor arguing that motive for murdering one’s rich husband is the same as pulling the trigger. Nor is this a case of an ID-er simply attacking evolution with no proof that design is involved — there are three notebooks on my desk, all the same brand and color, so I’ve labelled the spines with colored tape to keep them separate. Does this mean they “developed” tape as they sat on my desk?)
7 Responses to “Butterflies: teams and fallacies”
Ed Darrell on 27 Jul 2005 at 1:05 am #
Wow! I rate a mention!
I don’t have access to the Nature article either, but from the BBC story and several others it’s pretty clear what the researchers are looking at.
There are many species in the genus Agrodiaetus, so there is a lot of data to work from. The researchers discovered that where two different, non-interbreeding species of this genus are separated from each other geographically, often they look very much alike. This makes some sense — though there is speciation, the mutation may involve something other than appearance. Since in either location there is little danger that another, look-alike cousin will sneak in for breeding, there’s no need to expend the energy to develop a visible or other telling difference — and more critically, there is no need for natural selection to select for such a variation.
But where the two, different species sharea a breeding ground, they could get confused. Because hybrids in this genus generally are less-well adapted to live, hybrids breed less successfully than pure-breds. It is advantageous for the two species to quickly be able to distinguish one from the other; natural selection will select for a minor variation in the coloration of the wings.
This is similar to the mechanism by which the herring gull and the lesser black-backed gull distinguish their own (this is a famous ring-species example).
Incidentally, variation in wing design and color appears to be one way by which butterflies frequently diverge, even in subspecies and even, sometimes, in the same populations. Mutations quickly produce differences.
The observation is not made to previous generations, yet. That observation may be done with a DNA comparison. Instead, the observation of the researchers is made on the basis of comparing several diferent populations, both of one species in the genus being present, and with two species from the genus being present.
There is no intelligent design explanation for the differences, by the way. There is no lepidopterist who is an advocate of ID. There is no research into butterflies being conducted either by ID advocates or by other creationists.
Wallaby on 27 Jul 2005 at 11:09 am #
Yes, that does a good job of summing up the BBC article. The point still remains — this is a case of a biologist observing a difference, coming up with a reason for the difference (a way that the difference improves the success of both populations), noticing that other butterflies don’t have such a feature, and concluding that therefore, this difference must have evolved.
Now, I’m not a lepidopterist. I’m not even a biologist, although I’ve got a degree in that subject too. Perhaps the rules of science are different in biology. However, any time when “science” involves saying, in effect, that there’s only one possible explanation for the data because that’s the only one that we’ll allow ourselves to consider — well, there are reasons why I lost interest in biology before I even finished my BS in it.
As I said, I’m not a lepidopterist, and I wouldn’t even describe myself as particularly committed to ID. Even so, it’s pretty easy to come up with an ID-based explanation, or even several –
*Aliens landed where these butterflies lived, collected specimens of them, got confused by which was which, so they incorporated genes to mark their wings with different patterns.
*Invisible pixies who live in the grasses thought that the butterflies were a little too drab, so they paint the butterflies’ wings while they sleep.
*There exists some hitherto-unknown Butterfly Deity, who has chosen these two particular species as its own special servants. The different colors indicate different priestly castes. Other Agrodiaetus species are not so favored.
None of these has any connection to a creationist argument; they all suit the basic pattern of ID. Of course I can’t prove any of them (yet) — but then, the evolution-happy lepidopterists still have miles to go before actually “proving” their explanation, instead of constructing a plausible hypothesis.
I suspect that the short supply of lepidopterists willing to use ID as an explanation is due at least in part to the relatively short supply of lepidopterists in the first place, compared to (for intance) biochemists. Good thing science isn’t about having numbers on one’s side — we’d still be looking for phlogiston instead of dark matter.
Ed Darrell on 27 Jul 2005 at 6:40 pm #
Especially if you’ve read Jonathan Weiner’s excellent, Pulitzer Prize-winning book, The Beak of the Finch, you understand that often the mutations by which we mark species after the fact of speciation may be mutations that occurred long after the speciation and may be wholly unrelated to the speciation event.
However, in this case, there are observations as to how the butterflies pick their mates. It’s fair to say that the bar on the wing makes the difference.
Since we know that all other markings on the wings got there evolutionarily, from dozens or hundreds of other observations and experiments, it seems to me it’s fair to say that these bars got there the same way.
Mutations have been observed to make such differences. No pixies have ever been observed. No aliens have ever been observed to make such a difference. No butterfly deity has ever been observed to make such differences.
So, with positive evidence that such mutations appear evolutionarily, it’s fair and reasonable to dismiss the three ID solutions you propose until such time as you can offer evidence that such ID solutions have ever occurred.
I think you’re starting from an unwarranted assumption that lepidopterists don’t know how markings on butterfly wings occur. You’ll want to get a copy of the paper, I think, and see what the authors cite on wing markings. If you check the abstract, you’ll see that this genus was chosen specifically because it offers a chance to study exactly this issue (Here’s the PubMed data:
Other good news is that this paper’s lead author is from the former Soviet Union and it covers material that, during the Stalin era, would have got the authors jailed, exiled or shot. It’s nice to see a recovery of Russian science from the anti-Darwin mania that ultimately led to the starvation of millions of people. There’s a moral there, somewhere, for people who wonder why biologists get exercised when ID advocates offer to censor science.
Wallaby on 27 Jul 2005 at 10:16 pm #
As expected, the BBC science writer grossly oversimplified the original paper, which shows rather more in the way of detailed experiments than I’d expected. The main focus of the paper isn’t the “team stripes” at all, as the abstract (and the paper) makes clear.
“Mutations have been observed to make such differences. No pixies have ever been observed. No aliens have ever been observed to make such a difference. No butterfly deity has ever been observed to make such differences.”
As clearly seen by the lack of butterfly-deity theologians.
Mutations have been observed to cause phenotypic changes, yes. This is familiar ground, and I don’t think I was denying this now any more than I was a few weeks back. What struck me about the “discovery” (as reported in the BBC article) was that
1. The use of “it was useful, therefore it evolved” as an explanation seems needlessly complex in this particular case, inasmuch as simpler explanations can also be made;
2. The “proof” of evolution (in both the popular press version and the actual paper) amounts to “a number of similar butterfly species show differences in genetic similarity which can be used to construct a phylogenetic tree on the assumption that they evolved, therefore these species have evolved in this particular way”. Circular reasoning, any way you slice it.
This isn’t to say that the phylogenetic work presented here isn’t impressive, or that I have any particular argument with it. It’s quite reasonable to make detailed comparisons of genetic structure, or wing morphology, or whatever, and use that to conclude that species A is more similar to species B than either is to species C. It’s when this is coupled with the assumption that the degree of similarity is a useful estimate of when two species diverged (which rests on the assumption that they *did* diverge), that the reasoning becomes circular.
(Am I denying that mutation causes changes? Nope. Am I saying that such changes can’t, at least in some cases, lead to speciation? Nope. Just saying that “this is sometimes seen to occur” is not the same as “this happened N million years ago”.)
I’m sure that lepidopterists do know what causes wing markings, which is why I was disappointed to see the complete absence of any specific details on how such particular wing markings might’ve developed. It goes a good ways towards explaining how it is that the species have stayed distinct, and fills in the gap in my awareness of butterfly sexual behavior. However, there’s no details whatsoever on the pigments responsible, or any suggestion of how such a mutation — presumably affecting the genes that lead to deposition of pigment materials in specific spots — occurred. Of course, it’s just a letter to Nature, not a complete textbook.
As far as the specter of ID advocates attempting to censor science — It wasn’t ID advocates who raised a huge fuss over the Meyer paper; it wasn’t ID advocates who raised a huge fuss over the Smithsonian showing a film reported to contain ID-friendly arguments. Oh, right, sorry — that was Real Scientists discouraging the disreputable efforts of the ID-ers to bring in a wider range of explanations. Or even to encourage students to question whether the orthodox explanation is truly adequate.
Yes, it’s nice to see that genetic research is now being done in Russia. Of course, the “anti-Darwin mania” wasn’t exactly an outbreak of creationism. The Soviets would’ve objected not so much because of the scandalous notion that mutations cause organisms to change, but because they were convinced that research on the karyotypic differences between butterflies does not, somehow, lead to ending endemic famine. Still, it’s nice to know you’re so careful to follow along when Sagan says that they’re equivalent.
Ed Darrell on 01 Aug 2005 at 11:37 pm #
Well, no, this isn’t the paper that talks about the ins and outs of wing markings. But if you check the footnotes, you’ll see that work has been done and you can check it out (see notes 14 & 25, 15, 27). The paper is, instead, and contrary to my first reading of the abstract, a work based on the genes of the 89 species and subspecies. This is exactly the sort of detailed work that no one in “intelligent design” has ever proposed to do in any aspect.
I think that a careful reading of the sources noted would provide the background work on the actual genetic sources of much of the coloration, and one would see that there is no circular argument made anywhere. You’ve got the paper, and you can track down the sources better than I.
As to censorship: The Meyer paper is garbage and shouldn’t have been published. Pointing that out, especially after it was published, is not censorship in any way. In point of fact there have been only two papers on intelligent design submitted to journals — and both were published. That’s a 100% rate. There is no censorship there. The amazing, almost incredible dearth of papers (two papers in 15 years) is due entirely to the spectacular lack of research on intelligent design by intelligent design advocates. If there is censorship, it’s self censorship.
Again, with the showing of the ID film at the Smithsonian (though ID advocates now argue it isn’t really an ID film — go figure), it was an ID blog run by Denyse O’Leary that made public the claim that the Smithsonian had endorsed the idea of intelligent design. That’s a false claim, of course — but it was not censored. The film went on as planned. I don’t think pointing out a false claim is censorship, is it? That certainly doesn’t match the dictionary or legal definition.
Students are free to question the “orthodox” explanation of evolution — but teach the facts first. ID advocates tesetifying in Texas asked to censor the textbooks, to get evolution out and insert garbage instead. Same thing in Kansas in 1999, same thing in Ohio in 2002. Same thing in Georgia in 2003. Same thing in Pennsylvania this year.
In all those cases, science journals would be happy to publish research on intelligent design — remember, there is a 100% success rate of getting such papers published — but there are no papers in the mill. Michael Behe told me in 1999 that he would have a paper proposing a hypothesis for ID out within a year. In 2003 he said it was months away. Now he says nothing is in the mill. What gives?
Stalin’s campaign against Darwin had almost nothing to do with the science. As Lysenko explained, Darwin was out because man’s abilities and behaviors could not have arisen by biological evolution. So far as that statement goes, it agrees exactly with orthodox creationism and differs not at all from intelligent design. Creationists and IDists claim we get from a deity what Lysenko said we get from “social evolution.” Stalin and Lysenko banned discussion of human evolution — shades of creationist Tennessee Gov. Austin Peay! — and rewrote the textbooks to exclude Darwin as “too bourgeois.” In Texas, creationists and IDists proposed to get Darwin out as “leading to immorality.”
The parallels between creationism/ID and Lysenko’s errors are much greater than the differences. Both are completely sterile as science, too.
Wallaby on 02 Aug 2005 at 1:56 pm #
Hurrah for evolutionary biologists putting in long hours of PCR. That’s also the sort of detailed work that’s been done thousands if not millions of times before, which is perhaps why it was published as a letter instead of an article. It’s not the sort of detailed work that would be tried by someone testing a hypothesis that the wing markings were different by design, because it’s not capable of providing that information.
I’d be curious to hear what your grounds are for dismissing Meyer’s paper as “garbage”, when multiple biologists found it a significant contribution:
(From Sternberg, the former managing editor responsible for publishing it.)
It was only after the fact that the biology community panicked about a paper challenging orthodox evolution.
Now, as I’ve pointed out before, the simple fact that a couple other scientists thought some particular bit of work was good doesn’t actually make it so. In this case, none of the reviewers agreed with Meyer’s conclusions, but they all agreed that the work itself was well done. So, what are your grounds for disagreeing?
Pointing out that a paper’s methods or conclusions are faulty isn’t censorship. A journal repudiating publication of a paper after orthodox biologists squawk, including arguments that directly contradict the managing editor’s statement — that’s about as close to censorship as one can get. Note that the BSW promised that intelligent design would not again be addressed in Proceedings. Shutting down the debate, whether or not they’re confident that evolution can stand up to scrutiny.
Yes, the film went on as planned, and no, it didn’t actually have much to do specifically with ID. (Films which don’t parrot the standard model, or which don’t specifically endorse Darwinian evolution, are not automatically “ID films”. There are various differences between the anthropic principle and intelligent design that I’m sure you’re too scientific to be bothered with, since you don’t seem aware of them.) There sure was a concern about the film being shown, though — perhaps more so about the (hyperbolic) claim that the Smithsonian was “endorsing” ID.
I’m not, alas, responsible for Michael Behe’s work, and the timetable for its publication. I’m sure that your own scientific work has included instances where a line of inquiry proceeds more slowly than you would have hoped, or at least that you can imagine it if you haven’t actually done such work. He’s published other work in the meantime, although it hasn’t involved detailed cladistics experiments based on hypotheses to which he doesn’t subscribe.
The Biological Society of Washington banned discussion of intelligent design in its journal — shades of Stalin and Lysenko! It really seems quite simple, to someone with an open mind — *if* “macro” evolution is a correct explanation for the presence and diversity of living organisms, then it will be proven true despite the investigation of competing explanations (ID, Lamarckian evolution, whatever). This pattern’s been seen countless times in other scientific disciplines — Lavoisier didn’t try to advance his theory of oxygen by preventing discussion of phlogiston, which eventually died a natural death when nobody could deny it was wrong. In the meantime, Darwinian evolution isn’t less true because some scientists question it; it can’t be truer than it is if every single person on the planet believes it. However, establishment biologists seem genuinely terrified that people will listen to alternatives.
No, ID supporters shouldn’t work particularly hard to get Darwinian evolution out of public schools. For better or worse, that theory’s going to pervade biology for the next hundred years or more, and it’s very much a disservice to the students to leave them completely unaware of it until they get to college.
On the other side of the aisle, Darwinian evolutionists should be objective enough to admit that there are still details which they can’t give thorough explanations for.
(That’d be explanations that don’t begin with “Given enough time…” or “It provided a reproductive advantage”.) Instead they plug their ears and chant “not science! not science!” whenever someone whispers “is this really enough explanation?” Or requests stickers for textbooks urging that students think about what’s inside.
Three responses to you (on anything) really is enough.
Ed Darrell on 04 Aug 2005 at 4:11 pm #
I dismiss Meyer’s paper because it is not good research. It’s not research at all (you’ve read it?). I dismiss it because the society that published announced that it had been published outside the rules of the society and that they would not have published it had ordinary processes been followed. I do not know why Dr. Sternberg chose to publish it in his last edition as editor — but there you have it. I also do not know the names or reputations of those who are alleged to have given the thing peer review — but I do know that it was not in the realm of expertise of the society, according to the society, and that critics of intelligent design in the several areas the paper touches on were not invited to review the paper, which would be normal procedure in most biology societies.
On what possible grounds could anyone defend it? It lays out no research backing intelligent design; it lays out no research at all. It lays out no intelligent design hypothesis that can be tested. It lays out no possible outline of hypothetical theory based on testing to be done later. Could a paper that proposes intelligent design in chemistry, which offers no experimental data, and no hint of a testable hypothesis, be considered good enough to contradict molecular theory?
If two papers in 15 years is enough to justify defending intelligent design, then why are you not thumping the tub for cold fusion as well? There are 10 times as many papers with favorable experimental results backing cold fusion. Indeed, intelligent design is rather the cold fusion of biology — just lacking the experimental and theoretical justification that cold fusion has.
BSW said the subject matter was inappropriate for its journal. Generally they publish papers on classification of living things. And, if we are to believe Sternberg to be a competent editor for such a journal, it’s clear that when it departs from its area of expertise, it can get hornswoggled. (I leave it to others to determine whether Sternberg is the hornswoggler or the hornswogglee — it doesn’t matter in the greater scheme of things.) I wish the society had not been so forceful in saying it would not publish ID material in the future. I can imagine a situation in which, were ID to actually get a theory and research backing it, classification of living things might make mention of the theory under which things are classified. But I have a vivid imagination. I don’t find it fair, nor a defense of ID, to claim that a journal’s refusal to err again is censorship. The Journal of the Air Pollution Control Association probably won’t publish ID stuff, nor will any journal of electrical engineering. That’s not censorship, it’s wise discrimination.
On the other hand, why is it that intelligent design can only get two articles in 15 years? Why are not the researchers working in the area pounding down the doors of the journals to get the stuff in print? Were ID accurate, there’s at least one Nobel there for the guy who gets to the presses first. Michael Behe has a lot of publications, so he knows the path to the journals’ doors, when he has stuff to look at . . .
ID advocates should be wise enough to admit that of the many things biologists don’t know and which Darwinian theory has not answered, there is nothing for which intelligent design offers any better answer, or any light at all.
When ID advocates do some research and get some results, it will be published. Until that time, it’s an exercise in either fantasy or dementia to pretend something exists where it does not. We live in a competitive world. South Korea has now surpassed US researchers in cloning technology, and the entire world has surpassed us in stem cell cure research. We capitulate areas of knowledge only at great risk to the industries involved — agriculture and medicine in this case.
No biologist has plugged any ears when presented with data from intelligent design research. There has never been any such research. Biologists are concerned at the political attempts to get around science. Intelligent design has failed in the marketplace of science ideas so far — it doesn’t deserve a special pass from any Kommisar of Science to advance farther than its research merits.