Scientists: Surgeons not out of a Job Anytime Soon—Or Why that Appendicitis Still Hurts.

| 41 Comments | 1 TrackBack

By Douglas L. Theobald, Assistant Professor of Biochemistry, Brandeis University

“Its major importance would appear to be financial support of the surgical profession.”
—Alfred Sherwood Romer and Thomas S. Parsons, The Vertebrate Body (1986), p. 389.

A recent science news article from the Associated Press reports on a novel hypothesis (Bollinger et al. 2007 JTB in press) concerning the possible function of the human vermiform appendix. Given how much creationists dislike all things vestigial, the Bollinger paper will undoubtedly be paraded on anti-evolution websites with grandiose claims about how “researchers are declaring that they have found a purpose for the human appendix”—and the paper itself unfortunately provides several tasty quote-mines ready to be plucked.

The new hypothesis, to be published in the Journal of Theoretical Biology, was proposed by a group of immunologists and surgeons from Duke University Medical Center. Bollinger et al. suggest that the structure and location of the human appendix has been specifically modified for an adaptive function, namely for housing and preserving beneficial gut bacteria during certain pathogenic infections that otherwise would clear the bowel of all enteric bacteria. Evidently, individuals who had an appendix would have a selective advantage over those individuals who had either no appendix or who had a larger appendix with a larger opening. Presumably after, say, an epidemic of amoebic dysentery, individuals with such an optimally sized appendix would be better able to repopulate the gut with good bacteria and to recover (this is an adaptationist paraphrase; the authors don’t use explicit evolutionary terms). The authors were led to this hypothesis after they noticed that human appendixes (yes, that’s the proper plural for the anatomical structure) contained significant bacterial biofilms, which are notorious for allowing bacteria to withstand all manner of malign assaults, including vigorous mechanical cleaning and chlorine bleaching.

There are two important points to be made about the Bollinger et al. paper, both of which have been completely lost in the wash of media hype. First, this is purely a hypothesis paper, and, aside from cursory physiological plausibility, as yet there is no empirical evidence for the hypothesis whatsoever. A novel hypothesis was proposed; nothing has been scientifically demonstrated. And, in practice, it will be extremely difficult to test this hypothesis. [Note: a point explicitly made by the authors]. Second, even if the authors are correct—that this is a bona fide adaptive function for the appendix—-there is absolutely no basis for the claim that the appendix should no longer be considered a vestige. Quite to the contrary, the proposed function offers even more evidence for the vestigiality of the human appendix.

The proposed adaptive function is no silver bullet

First, the good news. Given the facts, the Bollinger hypothesis is plausible. In fact, from my reading of the literature concerning the possible functions of the appendix, their hypothesis, though imperfect, seems by far the most likely for an adaptive hypothesis specifically. All the other currently favored adaptive hypotheses for the function of the appendix are also immunological. But these others are problematic for two big reasons: (1) the evidence for functionality is wholly based on animal models, like rabbits and mice, whose “appendixes” are not homologous with the human appendix, and (2) they propose a function that is evidently also served by the rest of the cecum/colon. In other words, the function proposed is something that the appendix might do, but the function is not specific to the appendix per se. In contrast, this new Bollinger et al. adaptive hypothesis is the best going because, unlike the others, it is based on human physiological data and because it proposes a reasonable function specifically for the appendix as a distinct structure from the rest of the gut.

However, adaptive explanations are not the only possible explanations. Other plausible, non-adaptive explanations for the appendix exist, and there are some significant problems and questions here for any adaptive explanation that purports to explain the continued existence of the human appendix.

For example, without modern medicine, the mortality rate due to appendicitis would be between 3-10%. This is extremely strong selection against having an appendix. If selection is the only thing at play in maintaining the appendix, then, all else equal, the proposed function must have an even greater positive selection pressure to compensate. But it is hard to see how a “protected safe haven” of bacteria could be so beneficial. Presumably, during an infection that clears the bowel of bacteria, some small fraction of bacteria would be left. Is that fraction really so small compared to the amount in the appendix, the interior volume of which has been compared to the size of a matchstick? The proposed function would also be most effective when intestinal illnesses like dysentery or cholera are frequent. Was this the case for Holocene hunter-gatherer societies, which likely wouldn’t have the water-contamination problems characteristic of modern epidemics? Not just humans, but all hominoid apes have a vermiform appendix (that’s gibbons, orangutans, gorillas, chimps, and humans)—and so the proposed function presumably existed during the last 20 million years of ape evolution. Are severe diarrheal illnesses common in apes?

Ultimately, in order to firmly establish empirical evidence for an adaptive function for some structure, evolutionary biologists stipulate that several necessary requirements must be met:

  • Phenotypic variability: If there is no variation in a given structure, then selection has nothing to choose from.
  • Heritability: There can be strong selection for a trait, but if the trait is not inherited, it won’t increase in frequency in subsequent generations (at least not due to selection).
  • Differential fitness (like mortality) based on phenotype: If all the variants of a structure have the same impact on fitness (e.g., none of them help or hinder, relatively, their bearers in reproductive terms), then there is no selection. And finally,
  • Non-random change in frequency: It’s possible that the first necessary three requirements are fulfilled, yet the structure still doesn’t evolve in a non-random, selection-driven manner (the classic example is in small populations, where genetic drift dominates and can override selection).

So what is the relevant evidence regarding the appendix?

  • How much variation is there in the size of the appendix? Quite a bit. Typically, the human appendix ranges anywhere between 2-7 inches in length, but it is not uncommon to find one under an inch or nearly a foot long. There are many documented, though rare, cases of congenitally absent appendix, where a person is born completely lacking one. So far so good.
  • Are variations in the structure of the appendix heritable? Though it is reasonable to think so (typical heritabilities for morphological traits are around 1/2), to my knowledge nobody has ever looked at this specifically.
  • Is there differential survival among people who lack an appendix versus those who have one? For example, are people who lack an appendix more likely to die from intestinal illnesses? One way to look at this would be to study whether individuals who’ve had appendectomies recover less often from, say, amoebic dysentery or cholera. Nobody has done this analysis yet, and in fact this would be particularly hard to test. Even if a correlation was found between appendectomy and mortality due to dysentery, this wouldn’t establish that lacking an appendix was the problem. It’s likely that people who are susceptible to appendicitis are generally more susceptible to intestinal problems overall. Ideally we’d want to look at people who had healthy appendixes removed incidentally, which would mostly eliminate possible artifactual correlations between appendicitis and mortality.
  • Finally, do we see evolution in appendix size after a selection event? For instance, after an epidemic of cholera, are fewer people in the population born without appendixes, or does the average length/volume of the appendix increase? Nobody knows.

Again, there are other plausible, yet non-adaptive, explanations for the appendix too. The appendix may simply be a detrimental product of historical contingency, similar to other things like crammed wisdom teeth, birth canals narrower than a baby’s head, slipped discs, tail bones, and prostate trouble. Developmental constraints can prevent the complete elimination of a structure—perhaps the mutation that would finally dispose of the appendix is correlated with development of the rest of the gut, and would eliminate the colon too. Perhaps we’re stuck in a local minimum of sorts, unable to get to the global minimum. For example, some researchers have proposed that the appendix would decrease in size, eventually being eliminated, were it not for the fact that small appendixes are more prone to appendicitis (they get blocked and infected easier)—so there is antagonistic negative selection that prevents complete elimination.

All of the above considerations underscore just how difficult it is to establish a true adaptation, how high the evolutionary bar is set for empirical demonstration of function, and how outrageous it is when we see headlines like “Appendix protects good germs” or “Scientist’s [sic] find appendix’s job”.

The appendix can have a function and be vestigial

Bollinger et al. imply in several places (five exactly, including the abstract) that the human appendix should no longer be considered a vestigial structure. This appears to be due to a common misunderstanding of the vestige concept.

A vestige can have important functions—complete non-functionality is not (and never has been) a necessary requirement for a vestigial structure. “Vestige” is a word that has Latin roots and literally means “footprint”, a trace of something. The key, defining element of a vestige is that it has lost an important function. A vestige can only be identified via comparative analysis, as a reduced and rudimentary structure compared to its homologs, one that lacks the complex functions usually found for that structure in other organisms. In discussions with Bill Parker (senior author on the Bollinger et al. JTB paper) and Seth Borenstein (AP reporter), I discussed analogies with bird wings/forelimbs that I think are very instructive.

Everyone agrees that an ostrich’s wing is a vestige—ostriches have wings, which are meant for flight, yet ostriches cannot fly. Nonetheless, ostrich wings may have several important functions: they are used in courtship displays for securing a mate, they shield young birds from the intense desert sun, they enable very quick lateral maneuvers when running at speeds up to 40 mph, and two of their wing digits terminate in fiercely sharp claws that are used in defense. While possibly very important, all of these functions were likely present in the flighted ancestors of the ostrich.

A similar, yet tellingly different, situation is found in the penguin, which has “wings” that have become highly modified for underwater swimming. A penguin’s forelimbs, its flippers, clearly evolved from wings in an ancestral bird, yet a penguin can no longer fly. However, and here is the important difference, the penguin’s flippers have gained an important function that its ancestors did not have—the penguin is an incredibly efficient and skillful underwater swimmer. Penguin flippers are homologous to the wings of birds that can fly, but they are not really vestiges.

Now here are the important lessons:

  • Ostrich wings are vestigial because they have lost an important function, because they are organs with a particular structural arrangement that evolved for a different purpose—a purpose they no longer serve.
  • Ostrich wings are vestigial even though they may perform important functions.
  • Penguin flippers are not considered vestigial, primarily because they have gained an important function that is not found in the ancestral state (and they have been highly modified for that function).

How does this relate to the present Bollinger hypothesis? Analogous to the situation in both ostriches and penguins, the human appendix has lost an important function, namely cellulose digestion (for background and detailed explanation, see “The vestigiality of the human vermiform appendix”). If the Bollinger hypothesis is correct, then the appendix also performs an important immunological function. But is this function “new”, or was it present in the ancestral, cellulose-digesting primate cecum? If the function is new, analogous to the penguin case, then the appendix can’t really be considered a vestige. If the function is old, analogous to the ostrich case, then the appendix is still a vestige. Here is how William Parker puts it:

There is virtually a 100% chance that if we are correct regarding the function of the human appendix, then the cecum of other animals fulfills the same function as the appendix of humans. In fact, much of our data are taken from non-human studies in a variety of species.

It is apparently a case of an organ being good at two functions (bacterial preservation and digestion) evolving to more efficiently carry out only one of those functions (bacterial preservation) while losing the other function (digestion) completely.

In other words, we have here a case that is perfectly analogous to the vestigial ostrich’s wings.

One final note of irony. The authors state that their proposed function is no longer needed in modern society. So, if correct, this would mean that the appendix is doubly vestigial.

References

Acknowledgments

I extend a warm well of gratitude to the many cantankerous PT regulars who gave much help and input for this post, including, in no particular order, PZ Mayerz, Larry Moran, Pete Dunkelberg, Steve Reuland, and Mark Isaak. I have paraphrased many of their very comments. I also thank Bill Parker for allowing me to quote him, and for amiable discussion.

Notes

  1. ” However, absolute proof of such a function may be difficult to obtain since the unique nature of the human appendix may preclude the use of animals to study the issue. Further, it is anticipated that the biological function of the appendix may be observed only under conditions in which modern medical care and sanitation practices are absent, adding difficulty to any potential studies aimed at demonstrating directly the role of the appendix in humans. “

1 TrackBack

New on...science blogs from A Blog Around The Clock on October 12, 2007 10:39 PM

Jonathan Eisen, Rosie Redfield and Douglas Theobald destroy the especially egregious example of bad media reporting on the "function of appendix" paper. Kate does not dance around the issue when discussing a study on the relationship between lapdancers... Read More

41 Comments

“PZ Mayerz”? I thought the post was excellent up to that point. Here is Google’s response to a query on PZ Mayerz: Did you mean: PZ Myers?

I think that’s a joke referencing the common misspelling of PZ’s last name.

I’m glad you posted on this. My own blog entry on the subject is somewhat shorter and more satirical. What I found particularly interesting is that the Uncommon Descent blog - albeit in a way that can easily be disclaimed if they need to - implicitly acknowledges that the existence of the appendix would fit naturally with evolution through natural selection. If it is still here, there would be no surprise if it had a useful purpose in the not-too-distant past.

http://exploringourmatrix.blogspot.[…]is-been.html

As expected, Darwinists will try to spin this around, and claim that this is the kind of thing “evolution would predict”.

Stay tuned!

Nice spin mats. But this is called projection…

JimV:

“PZ Mayerz”? I thought the post was excellent up to that point. Here is Google’s response to a query on PZ Mayerz: Did you mean: PZ Myers?

Yeah, its a joke. Long time talk.origins regulars often use very crazy misspellings of PZ’s last name to one up the people who misspell it every time.

So, Mats, what does Intelligent Design and or Creationism say about the function of the human appendix?

I have two questions about your first requirement for establishing an adaptive function for a trait, which was the need for phenotypic variability.

1. This is more of a question about theory. Variability is certainly required for any ongoing evolution by natural selection, but could not the selection have already occurred, resulting in near complete uniformity of that trait among the population? If this has happened, we certainly would not want to say that the trait is not adaptive.

2. This pertains to the specific case at hand. Since we see so much variability in the appendix today, doesn’t that in itself indicate that the human appendix is adaptively neutral? If it makes no difference to survival or reproduction, then the thing can be big, small, or whatever (within obvious constraints) and everyone survives just fine, passing on their weirdly-sized appendixes to their offspring.

Oh, yeah…one other thing. I like the suggestion of testing appendixes in a population before and after it has gone through a bad cholera outbreak. Even if the appendix had been a mostly useless vestige for much of our evolutionary history, perhaps in historical times when water contamination has been far more common than it (probably) was in the more distant past, appendixes are suddenly being subjected to selective pressures again.

One plausible suggestion for why the appendix doesn’t disappear (this recent reason does seem tenuous, if worth looking into) is that as it becomes smaller it becomes more prone to infection. And since few organs can “just disappear” at once, selection keeps the appendix at the present size just because smaller appendixes cause more trouble.

The appendix has for a long time not been my favorite vestigial, both because it’s hard to be certain that it has no important yet non-crucial function (even though I doubt it does), and because it’s kind of a weird thing that people don’t know much about. The coccyx, our vestigial tail, is so obviously a product of evolutionary constraints, that even if it does have minor functionality, it seems like a much better vestigial to bring up. People can visualize it well. Same with our vestigial hairs and their ability to stand on end, perhaps slightly functional (very low functionality at best), but so clearly is a vestige of our old ape-like coats that it’s fun to watch creos and IDists sputter and spin their implausible tales.

Other animals appear to have excellent vestigials, too, like useless teeth in juvenile platypuses and in unborn whales, legs in pythons, well, you know how it goes. True, it’s homologies again, none of which make sense from a design perspective, yet vestigial organs and genes are particularly poisonous for any ingenuous forms of ID or creationism. Then too, the bizarre fact is that vestigial genes are largely denied (with weaselly modifiers, however, so they don’t have to explain away specific pseudogenes) by IDists, while vestigial organs are, well, what their idiot designer would actually make, along with causing P. falciparum.

What they don’t get is that we need at least one example of such a strangely twisted “designer” before we can identify any such thing as a designer of any kind, if we’re being epistemologically consistent. What is it about analogies that they can’t get the fact that even a sensible analogy requires actually analogous causes for analogous effects, while disanalogous effects require similarly disanalogous causes (like evolution, for instance)?

Glen D http://tinyurl.com/2kxyc7

Mike Z: 1. … could not the selection have already occurred, resulting in near complete uniformity of that trait among the population?

I suppose technically yes, if you want to claim that the modern appendix is optimally suited for surviving cholera epidemics or whatnot. But that doesn’t make much sense to me, as you’d have to maintain that mutations that were able to introduce appendix variability in the past no longer occur today. At the very least, purifying selection should be at work, where non-optimally sized appendixes get weeded out.

2. … Since we see so much variability in the appendix today, doesn’t that in itself indicate that the human appendix is adaptively neutral?

No, not necessarily. The Bollinger argument is that it does make a difference to survival, but you have to have the right environment. Again, it seems like less variability after a cholera epidemic would be a positive sign.

which are notorious for allowing bacteria to withstand all manner of malign assaults, including vigorous mechanical cleaning and chlorine bleaching.

um, ok, so who was the unlucky volunteer that got the bleach enema?

An interesting post Douglas.

I gave up biology after 3rd form (not sure what the equivalent is in schools in the US) but I have learned a few things from your post re. creationist claims about vestigial organs. Speaking of which,they actually beat you to it and put this out on Monday: http://www.answersingenesis.org/art[…]7-quick-news

In a story that could be best described as ”well, what’s new?” researchers are declaring that they have found a purpose for the human appendix (www.foxnews.com). For years, creationists like Dr. David Menton of AiG have debunked the notion that the appendix is a useless leftover of our evolutionary past. Dr. Menton, who taught anatomy for decades at a prestigious medical school, has frequently echoed what many in the medical community have been saying for years: the appendix has a role to play in our gut-associated immune system. While we can live without the appendix when removed, it nevertheless serves a useful purpose.

Seems Dr. Menton has been “on the ball” long before anyone else !

It is possible that the appendix is a “corellation of growth” in that it is not posible to form a functioning mammalian (or primate) cecum without an appendix. Appendicitis although frequently lethal without surgical intervention does not by definition prevent reproduction as it does occur after reproductive age begins. Many more common illnesses in man also do not impede reproduction and are not going to be selected against and some other diseases do provide protection from even worse problems and will therefore have a slight advantage over “normal”. Appendices are remarkably uniform in their radiographic appearances although not in their location (including displaced by pregnanacy and malrotation). Good CT radiologists can find appendicitis because of this and therefore this imaging tool has become the “standard of care” in diagnosis in the USA (as opposed to ultrasonography) even where “classical” findings (vomiting, fever, leucocytosis, right lower quadrant pain and rebound tenderness) are lacking. Many gastroenterological infections such as salmonellosis and shigellosis occur even without “replacement” of the normal enteric flora (primarily E. Coli), while others (cholera, C. difficile enterocolitis) are due to toxins where nothing is actively “infecting” anything (analogous to diphtheria and tetanus). Even in amebic dysentery(E. histolytica), the total number of parasites never comes close to the E. coli still in the colon. Perhaps T. Smith can chime in on this but I can’t believe that there ever is a human GI tract totally devoid of normal bacteria. In fact all the readers of the thumb have more cells of E. Coli in their bodies than of H. sapiens.

John Hawks also has some thoughts on appendixes.

The proper plural is “APPENDICES”

“Appendixes” is homophonic with “appendices” and is an acceptable alternative spelling, according to the OED.

IIUC, it is an option for either meaning of “appendix” (whether the anatomical structure or the additional bit at the end of a book), but is more commonly used as the plural for the anatomical structure than the more literary meaning of “appendix”.

Plural of the structure, from the post:

The new hypothesis, to be published in the Journal of Theoretical Biology, was proposed by a group of immunologists and surgeons from Duke University Medical Center. Bollinger et al. suggest that the structure and location of the human appendix has been specifically modified for an adaptive function, namely for housing and preserving beneficial gut bacteria during certain pathogenic infections that otherwise would clear the bowel of all enteric bacteria. Evidently, individuals who had an appendix would have a selective advantage over those individuals who had either no appendix or who had a larger appendix with a larger opening. Presumably after, say, an epidemic of amoebic dysentery, individuals with such an optimally sized appendix would be better able to repopulate the gut with good bacteria and to recover (this is an adaptationist paraphrase; the authors don’t use explicit evolutionary terms). The authors were led to this hypothesis after they noticed that human appendixes (yes, that’s the proper plural for the anatomical structure) contained significant bacterial biofilms, which are notorious for allowing bacteria to withstand all manner of malign assaults, including vigorous mechanical cleaning and chlorine bleaching.

Peter Henderson: Vestigial does not mean useless. According to Dictionary.com: Biology. a degenerate or imperfectly developed organ or structure that has little or no utility, but that in an earlier stage of the individual or in preceding evolutionary forms of the organism performed a useful function.

Basically a vestigial organ is something that does not perform its original function, like hips in whales. Whales use their hips to help with mating, so they are not useless. But hips are used to attach legs to, but whales do not have legs. But since whales evolved from land mammals, and evolution is a bit of a sloppy designer, they kept their hips. Creationists love to claim that science says that vestigial organs are useless then proceed to show a use for them.

Even though this new finding is interesting, it is still at the hypothesis stage. We will have to wait for more research to come out to see if it is correct.

Vestigial does not mean useless

Yes, gathered that from Douglas’ post Gerald.

I only linked to the AiG article to show that they’ve alredy been buisy saying what you would expect them to say.

Oops, sorry for the mix up Peter Henderson. I guess I’m used to forums where I often hear the old “vestigial means useless” story.

My nephew was born with a short “tail” that had to be surgically removed (doctor said it was not that rare). How do the intelligent designists and creationists explain THAT?

My nephew was born with a short “tail” that had to be surgically removed (doctor said it was not that rare). How do the intelligent designists and creationists explain THAT?

I’ve told my wife (who’s an ex nurse) there are stories like this. She doesn’t believe me !

As expected, Darwinists will try

Creationists display their intellectual dishonesty in ways both big and small. One might write “As expected, they tried …” or “I expect that they will try …”, but Mats’s formulation treats his own fantasy about the future as a validation for his past expectations.

to spin this around

Spin it around from what?

and claim that this is the kind of thing “evolution would predict”.

Stay tuned!

You’re rather late to the party. People have been predicting for years that a function for the appendix would be found. Some of those people are adaptationists who expect features to have selective advantages, and some are creationists who think that all of God’s creation has a purpose. One question to consider is, which group actually does research and discovers such functions?

Popper’s Ghost proudly anounces:

People have been predicting for years that a function for the appendix would be found.

Yes. People like creationist Dr David Menton.

Some of those people are adaptationists who expect features to have selective advantages, and some are creationists who think that all of God’s creation has a purpose.

Adaptationists = Evolutionists in your worldview? So you are saying that the apendoix having a function is something that Darwinists always “knew”?

One question to consider is, which group actually does research and discovers such functions?

Pretty much anyone in the field, darwinist or creationist. But let’s assume that *all* major biological discoveries were made by darwinists. That is not the point. No creationist says that Darwinists don’t make scientific discoveries.

The point is:

1) Are those discoveries because or in agreement with the general darwinian assumption (that life forms are the result of a mindles/impersonal process)

or

2) Are those scientific discoveries in spite of Darwinian myths?

When you focus on who did the discover you are nicely trying to erase/re-write the Darwinian past. Don’t forget who were the ones who said that the apendix is “vestigial”.

Yes. People like creationist Dr David Menton.

fill in the blank:

a broken clock is still right __________

So you are saying that the apendoix having a function is something that Darwinists always “knew”?

No, but you’re saying you’re a moron, yet again.

Don’t forget who were the ones who said that the apendix is “vestigial”.

Did you even read the post, you ignorant cretin?

even if the authors are correct—that this is a bona fide adaptive function for the appendix—-there is absolutely no basis for the claim that the appendix should no longer be considered a vestige. Quite to the contrary, the proposed function offers even more evidence for the vestigiality of the human appendix.

One question to consider is, which group actually does research and discovers such functions?

Pretty much anyone in the field, darwinist or creationist.

I suppose that’s technically true, when there are no creationists “in the field”.

The point is:

1) Are those discoveries because or in agreement with the general darwinian assumption (that life forms are the result of a mindles/impersonal process)

Yes; read the post, moron. Or any of the other scientific literature.

2) Are those scientific discoveries in spite of Darwinian myths?

Have you stopped beating your wife, idiot?

Popper’s Ghost proudly anounces:

Since I pointed out that both adaptionists and creationists have made such predictions, why do you say “proudly”? And why do you misspell “announces”? I can understand that being stupid isn’t your fault, but why are you so dishonest, sloppy, and pig-headedly ignorant, and why do you troll here, frequently posting off-topic and arguing with people who are contemptuous of you and repeatedly justifying that contempt? What do you achieve by broadening the disregard of creationism and creationists?

So Mats, can you name even one scientific discovery that was made because of, or is even in agreement with the assumption that life is the result of an intelligent and purposeful process? Can you name any discoveries that were made in spite of creationist myths?

It bears repeating that the human appendix is regarded as being vestigial because it corresponds to the caecum of other mammals, such as the ones in rodents, horses, and koalas. The caecum is used to store digested food that passes in from the small intestines, where it is further digested by bacteria. In humans, our appendices can no longer do this, thus, it being regarded as being vestigial.

Of course, creationists ignore this entirely in order to continue their divinely inspired wankery.

Um. I don’t see how the appendix having a purpose helps creationists. Before the fall, there was no death and, consequently, no need for an immune system of any kind surely? So why did Adam need an appendix? This is a variation on the that theme of immense theological importance: did Adam have a navel?

Presumably the appendix arose AFTER the fall. Oh wait, evolution can’t increase “information” so Adam had a redundant appendix. The ways of the Lord are truly mysterious.

And medieval style arguments that determine the number of angels on the head of a pin are really tedious.

Um. I don’t see how the appendix having a purpose helps creationists.

Perhaps you don’t grasp the dishonest ad hoc nature of creationist argumentation. “We claim all of God’s creation has a purpose. The appendix has a purpose. That shows we’re right and God created it”. Pointing out the lack of logic, or pointing out something else that shows they were wrong, falls on deaf ears.

Perhaps you don’t grasp the dishonest ad hoc nature of creationist argumentation.

I think Ernest does Popper. He’s just shown how the creationist claim on the appendix having such a function just doesn’t make any sense by their own logic (i.e. no pysical death before the fall etc.) I think he’s made good point !

He’s just shown how the creationist claim on the appendix having such a function just doesn’t make any sense by their own logic (i.e. no pysical death before the fall etc.)

You’re as clueless as he is – it doesn’t have to make sense by logic to help them. Making sense by logic is our criterion for being useful, not theirs. As I noted, it’s helpful because it fits a slot in their “argument” that goddidit. It doesn’t have to logically follow that goddidit; the argument doesn’t have to be sound, or valid, or make sense, or be logical, it only has to be articulable. It’s cargo cult logic – only form, not substance, matters.

The proposed new ‘function’ is actually very lame, given the microbiology of the human gut. Even a very severe diarrhoeal infection will eliminate no more than 99% of the gut bacteria, and no more than 90% of the bacteria in biofilms. Thus the millions and millions of bacterial cells remaining in the gut will be plenty to repopulate it, with no help needed from biofilms in the appendix. Furthermore, the guts of people living under primitive conditions will quickly be repopulated from the environment and from other members of the society, especially because severe diarrhoea will have contaminated the environment with fecal matter.

All it says is

Presumably after, say, an epidemic of amoebic dysentery, individuals with such an optimally sized appendix would be better able to repopulate the gut with good bacteria and to recover

If there’s anything at all to that “better able”, it’s adaptive. But

this is purely a hypothesis paper, and, aside from cursory physiological plausibility, as yet there is no empirical evidence for the hypothesis whatsoever

So I think “lame” is redundant. :-)

Allison Hardscrabble:

My nephew was born with a short “tail” that had to be surgically removed (doctor said it was not that rare). How do the intelligent designists and creationists explain THAT?

Obviously your nephew is half ape. An Abomination in the Eyes of the Lord, etc. A lot of the variations in the human form start to look like abominations if you believe every species - and every race - resulted from a separate act of creation. We’re arguing about bones when the real problem is that a few people want to believe that they are “chosen.”

Re “Obviously your nephew is half ape.”

Non-human apes don’t have tails either, afaik. ;) (Or at least no more often than humans do.)

Henry

I’m not sure if I agree with Rosie Redfield. I take the term “primitive conditions” to mean those of nomadic hunter-gatherers with small populations. Risk of contact with fecal matter would be very low. It’s mainly in cities that you find epidemics of intestinal infection. A problem that is still prevalent today. Perhaps it would be worthwhile checking the appendixes/appendices of people from, say India. If it has any immunological function, it would still be useful today in many countries, despite the “note of irony” mentioned above.

Dr. Theobald wrote another fantastic article, the appendix can have an adaptive function and still be ‘vestigial’, no intelligent evolutionist would claim that ‘vestigial’ is synonymous with ‘worthless’, to imply that vestigial structures have no function or purpose. He is spot on with regards to an ostrich’s wings.

“Everyone agrees that an ostrich’s wing is a vestige—ostriches have wings, which are meant for flight, yet ostriches cannot fly. Nonetheless, ostrich wings may have several important functions: they are used in courtship displays for securing a mate, they shield young birds from the intense desert sun, they enable very quick lateral maneuvers when running at speeds up to 40 mph, and two of their wing digits terminate in fiercely sharp claws that are used in defense. While possibly very important, all of these functions were likely present in the flighted ancestors of the ostrich.”

About this Entry

This page contains a single entry by Guest Contributor published on October 9, 2007 9:20 AM.

Unacknowledged Errors in “Unacknowledged Costs” was the previous entry in this blog.

Retrospectacle for Blogging Scholarship is the next entry in this blog.

Find recent content on the main index or look in the archives to find all content.

Categories

Archives

Author Archives

Powered by Movable Type 4.381

Site Meter