…and this is a 
Since I just chastised the misleading presentation of this paper in the press (and I must emphasize that the odd focus on Darwin is not in the paper at all), we can now take a closer look at the paper itself. The data is actually cool to see, and represents a large amount of work; I still have some criticisms for the interpretation, though. The fundamental question is whether the structure of the appendix was specifically selected for, and the authors are on the side of 'yes'. I'll come down on the side of 'maybe'.
But first, an important caveat. Creationists have long been yammering about the appendix: they are absolutely positive that it must have an important function, because God wouldn't put it there unless it had a purpose. This paper will not help them. The heart of the work is a phylogenetic analysis of the distribution of the appendix in mammals which uses evolutionary theory: no evolution, this work vanishes in a puff of logic. If creationists try to claim this paper proves something they've been claiming all along, then they didn't read it and didn't understand it — it'll be a clear case of circular illogic.
To follow along with the story, you have to be clear on the layout of a small piece of mammalian plumbing. The little cartoon below illustrates the juncture of the small intestine with the large intestine, a portion of your gut that you'll find inside your abdomen on the lower right side.
When you eat something, it first goes into the stomach, where it's treated to an acid bath, some enzymes, and a lot of muscular churning to break it up. Then it's squirted into the small intestine (colored orange), where the acids are first neutralized and more enzymes are tossed onto the watery, mushy soup that the food has been rendered down into, called chyme. The primary job of the small intestine is to suck all the nutrients out of the chyme and pass them on to the circulatory system.
Once as much of the good stuff has been leeched out of the chyme as your system can do, the soup is passed on to the large intestine (salmon colored in my cartoon). This stuff is still very watery — if you've ever experienced diarrhea, that's what it is at this point. The primary job of the large intestine is to resorb water from the waste, condensing it down into the thick, pasty glop we all know and love as excrement. The large intestine is basically the sewage treatment plant here.
The interesting thing about the transition is that it makes a couple of other odd dead-ends. The cecum (pink) is a small pouch that goes nowhere, while the appendix (red) is a slender projection from the cecum. These are variable in size both within a species and between them — some humans are born without an appendix, and within the majority that have them, there's at least a two-fold variation in size. Between species, the variation is even greater: most mammals don't have an appendix at all, and some have huge ceca and appendixes. The enlarged cecum in most of these species is used as a fermentation chamber, in which hard-to-digest food resides while resident bacteria help break it down.
The diagram below illustrates some of these forms — to confuse you slightly, they're all upside down from my cartoon, with the appendix always drawn at the top.
The cecal appendix (a through l) or appendix-like structures (m through o) in a variety of mammals. The cecum ⁄ appendix is oriented toward the top of each drawing, the distal end of the small intestine toward the left and the proximal end of the large intestine toward the bottom. (a) human, Homo sapiens; (b) Pongo pygmaeus, orangutan; (c) Lepilemur leucopus, sportive lemur; (d) Lasiorhinus latifrons, Southern hairy-nosed wombat; (e) Oryctolagus cuniculus, rabbit; (f) Phalanger gymnotis, ground cuscus; (g) Anomalurus derbianus, scaly-tailed flying squirrel; (h) Trichosurus vulpecula, common brushtail possum; (i) Bathyergus suillus, Cape dune mole-rat; (j) Atherurus africanus, brush-tailed porcupine; (k) Castor canadensis, beaver; (l) Microtus pennsylvanicus, meadow vole, shown with a partially uncoiled large bowel; (m) Phascolarctos cinereus, koala; (n) Ornithorhynchus anatinus, platypus; (o) Tachyglossus aculeatus, echidna.
These images are taken from the Smith et al. paper, and illustrate its greatest strength — it consolidates a lot of scattered information about the distribution of appendixes in one place. They also discuss the variability of morphology; it seems there is some ambiguity in exactly what an appendix is. They used a strict definition of the appendix as "a relatively narrow and extended, close-ended structure at the apex of the cecum that is clearly distinguished from the cecum by a relatively abrupt change in the diameter of the bowel between the cecum and the appendix" and discovered that there were cases it did not cover. Some species had something that clearly looked like an appendix, but didn't have a cecum. Others had a a cecum that gradually tapered into a slender tube, lacking that abrupt change in diameter. That complicates the analysis, so they actually did two: one that used the strict definition and excluded some cases, and one that used a broader definition that included every species that had something vaguely vermiform dangling off the appropriate region of the gut. They then mapped the distribution of appendixes onto a consensus phylogeny of the mammals, and produced the tree diagram below.
The tree on the left is using the strict definition of an appendix, and the one on the right uses the broader definition. Taxa that have an appendix are in red, taxa in which there is a mixture of species with and without an appendix are in blue, and those without any appendix at all are in gray.
(Click for larger image)
Phylogenetic tree of mammalian relationships with appendicular characters mapped onto it. A mammalian molecular consensus phylogeny was taken, and appendicular and cecal characters were mapped onto the constraint tree as described in the Materials and methods. Results from Analysis 1 are shown by solid lines, which indicate the presence of a true appendix. Results from Analysis 2 are shown by the solid lines and by the checkered lines, the checkered lines indicating the presence of an appendix-like structure. On the left are shown results from analyses considering all taxa with variable expression of the appendix the same as taxa with consistent expression of the appendix. On the right are shown results considering all taxa with variable expression of the appendix as a separate state (indicated by the blue colour). Colour and pattern codes are as follows: grey, appendix absent; red, appendix present; red checkered, appendix-like structure present; blue, appendix variable; Blue checkered, appendix-like structure variable.
That's interesting: the only groups that have an appendix are the Glires (rodents and rabbits), primates, monotremes, and some marsupials. There's definitely a pattern to the distribution: it is not the case that the appendix is a random glitch in the organization of the gut, but is maintained consistently in some lineages for as long as 80 million years, and is consistently lost in others.
The data are useful to have and provide considerable food for thought; where I disagree with the authors is in the interpretation of that data. I don't think purely morphological data give us enough information to resolve the issues they bring up.
Here's what the authors conclude from that distribution. The most parsimonious explanation is that the ancestral state of mammals was to lack an appendix, so that the majority of extant mammals are exhibiting the primitive, appendix-less state. The appendix then independently evolved 2-4 times, with the lineages that acquired it also marked by frequent secondary loss of the structure. They argue that this necessarily implies an adaptive function for the appendix, otherwise it would not have been retained in so many of the primates and glires.
They also provide a possible function. In many cases where the cecum is very large, that function is digestive — this is an area of the gut that can be expanded into a fermentation chamber. In others, like us humans, it is too small to have that role, but what it may be is a small reservoir of bacterial biofilms that are resistant to loss during diarrheal episodes, and provide a source for rapid recolonization of the gut flora after disease strips them away. They have demonstrated the presence of biofilms in the appendix, and also in the proximal colon of outgroups that lack appendixes — so this property of supporting colonies of bacteria in this region of the gut is ancient.
I'm not entirely convinced. If the appendixes in marsupials and euarchontoglires are actually homologous, that should imply that their last common ancestor had a cecum/appendix…and the pattern is explained by widespread and frequent loss of the organ. The authors acknowledge this idea, but admit that there's also a problem with analyzing it: it depends on loss being far more likely than gain, and there aren't any probabilities that we can assign to such events. Fair enough. It does mean, though, that this analysis is insufficient to come up with an answer.
What I'd like to see is patterns of gene expression. That region in the plumbing where the small intestine becomes the large intestine is an interesting transitional zone which must be defined by some kind of patterning molecules; furthermore, I'd expect some kind of gene regulatory network has to be at work in that area to specify the different regions of small intestine, cecum, appendix, and large intestine. What are those genes? Which ones are expressed in the different regions? How do they interact and how are they regulated? You can see how my brain is turning over: I want to know about the developmental and molecular events going on here. That's where we'll be able to resolve the questions of appendix evolution.
I'm also unconvinced by the argument that retention of a feature for 80 million years is necessarily evidence of selection for a specific function. Another possibility is that it is entirely structural: there is a patterning pathway that sets up the transition from small to large intestine, and as a side effect it defines a few intermediate zones, the cecum and appendix. These are mostly harmless, and so are retained as entirely neutral characters that are not easily pared out without disrupting gut function. I say mostly harmless, because one lesson of the phylogeny is that a lot of lineages seem to have edited the structure out altogether. Again, it could just be loss of a neutral character, but it could also be an indication that usually, the appendix is a detriment.
A more solid answer would emerge if, for instance, the molecular networks behind the formation of the appendix in monotremes and humans were compared, and found to use the same toolkit of genes — then we'd have to regard it as highly probable that they are homologous, and the last common ancestor had an appendix. Or conversely, if the mechanisms used by the afrotheria, the xenarthra, and the other mammalian groups that lack an appendix to switch off appendix development were identical, that would suggest that the last common ancestor of the eutheria had that mechanism, lacked an appendix, and those euarchontoglires definitely did re-evolve the appendix.
Show me trees built from genes, then maybe I'll accept the interpretation with more confidence! I just think that one thing these data do show us is that the appendix is a remarkably labile organ, making the appearance or absence suggestive but not conclusive.
As for the argument that one function of the appendix that is significant in modern human populations is as a bacterial reservoir for recovery of gut flora after losses due to disease, that seems entirely reasonable. However, the fact that the appendix has an incidental function that can be useful to individuals in specific circumstances does not mean that the appendix isn't a vestigial organ, nor does it necessarily mean that its retention has been selected for. That some modern human populations have significant mortality from diarrheal symptoms (from cholera, for instance) seems to me to be a relatively trivial factor in a study that shows persistence of the appendix over many tens of millions of years, especially when no evidence of differential survival by individuals having or lacking an appendix is known.
I'm being a bit negative here, but it's largely because that distribution is so interesting and suggestive, and points the way to where we should be looking to answer the question of why we have an appendix. I also have my biases — I incline more to believing the organ is mostly neutral in us, and favor explanations based on the architecture of the gene regulatory networks — and would really love to see some molecular data behind the pattern (I also think it might resolve some of the complications and ambiguities of the morphology).
It's a good paper, but I get a rather different message from it. What it says to me is, "More genes! More development!" But then, I confess that that's what most papers say to me, anyway.
Smith HF, Fisher RE, Everett ML, Thomas AD, Randal Bollinger R, Parker W (2009) Comparative anatomy and phylogenetic distribution of the mammalian cecal appendix. J Evol Biol. 2009 Aug 12. [Epub ahead of print]
Life Science
Comments
Posted by: Celtic_Evolution | August 25, 2009 10:23 AM
So you're saying we should be seeing just such a proclamation from the DI any day now... right?
Posted by: Brownian, Most Vicious & Petty of Pharyngulites
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August 25, 2009 10:30 AM
Great piece, PZ. Now, do one on the evolution of the S aureus that infected me during my appendectomy.
*Grumble, grumble*...frakkin' med students, touchin' stuff and not scrubbing in again...*grumble*
Posted by: Brownian, Most Vicious & Petty of Pharyngulites
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August 25, 2009 10:32 AM
*Grumble, grumble*...frakkin' open HTML tags...*grumble*
Posted by: MK | August 25, 2009 10:35 AM
That was just an afterthought. Addendum in the plan.
Posted by: phein | August 25, 2009 10:38 AM
Ah, you forgot the most important purpose of all: To show us the need for God's existence, since a useless organ could NOT have evolved on its own!
[Somehow maintains straight face.]
Posted by: OctoberMermaid | August 25, 2009 10:41 AM
I can pretty much guarantee you that the only line that creationists will pay attention to is this, "I also have my biases..."
And then they'll go off on their little "Same data, different perspectives" creationist museum nonsense without ever thinking any deeper about it than that.
Posted by: Knockgoats | August 25, 2009 10:44 AM
The little cartoon below illustrates the juncture of the small intestine with the large intestine, a portion of your gut that you'll find inside your abdomen on the lower right side. - PZ
OK... *rummage, rummage* got it! Now, what did you want me to do with it?
Posted by: Alyson Miers | August 25, 2009 10:45 AM
If creationists try to claim this paper proves something they've been claiming all along, then they didn't read it and didn't understand it — it'll be a clear case of circular illogic.
Circular (il)logic is the only type that works! Let the data-twisting begin!
Posted by: Raynfala | August 25, 2009 10:49 AM
Show me trees built from genes, then maybe I'll accept the interpretation with more confidence!
I noticed we're talking about tubular structures. So, would balloon-animal analysis help seal the deal?
*ducks*
Posted by: Celtic_Evolution | August 25, 2009 10:52 AM
The paper does a good job of leading you towards likely conclusions, but I agree with PZ... I think there is more data that is needed before those conclusions can be seen as plausible or likely... as PZ noted, a follow on to this paper incorporating an in depth study of gene expression and molecular development will help ferret out the evolution of the appendix as function or structural by-product.
Interesting stuff... and once again, presented in a manner that a layperson such as myself can follow along and easily learn.
Posted by: Thorne | August 25, 2009 10:53 AM
Do you really think the Creationists will want to dirty their little minds with the details of an area of the body that is, quite literally, full of crap?
Posted by: Ten Bears | August 25, 2009 10:58 AM
Having recently had my appendix "lasered away", and twenty years ago suffered the freak out of a single parent having their child cut open... it has long been my understanding the cecum is much larger in earlier evolutionary iteration, and that it's primary purpose is in the digestion of raw meat.
"Hard to digest foods", omnivorous species... I'd have to actually see the dataset but there appears to be a pattern.
Posted by: Chris Caprette | August 25, 2009 11:02 AM
I agree with your reservations about the conclusion of this paper. It seems to me that one can readily recolonize one's gut after a bout of colon-cleansing diarrhea simply by eating. Many foods contain bacteria that normally reside in our gut. After all, how did the bacteria get there in the first place?
That some people do lack an appendix suggests that loss isn't necessarily maladaptive. So, we return to why do we keep it if losing it isn't harmful. I seem to remember some time in the not-to-distant past a paper (possibly one you posted about) that suggested that one reason humans retain a vermiform appendix despite the fact that it occasionally gets inflamed and ruptures was because gradual reduction of the organ would result in a higher frequency of obstruction and rupture. In this case, the only way to get rid of it safely appears to be a change in developmental regulation that prevents its formation entirely.
Anther thought, bowel diverticula (which the appendix is) are pretty common occurrences and frequently cause problems. Suppose that a diverticulum was fixed early in primate evolution, perhaps through a founder event or population bottleneck, and then for the reason mentioned above was never lost, no adaptation necessary? Just food for thought. Elucidating the regulation of development of this region of the gut would certainly help figuring out the answer to this question. You should get going on that right away :)
Posted by: NewEnglandBob
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August 25, 2009 11:07 AM
"maybe" isn't a side.
Posted by: Knockgoats | August 25, 2009 11:10 AM
The tree on the left is using the strict definition of an appendix, and the one on the right uses the broader definition. - PZ
Other way round, surely? The tree on the left shows some taxa with all members having an appendix, where that on the right has only some with an appendix - so the latter must be using the stricter definition.
Posted by: stogoe | August 25, 2009 11:11 AM
@15:
But if you choose not to decide, you still have made a choice.
Posted by: Eamon Knight | August 25, 2009 11:11 AM
Do you really think the Creationists will want to dirty their little minds with the details of an area of the body that is, quite literally, full of crap?
And this would be different from the normal contents of the Creationist mind in what way, exactly?
Posted by: pete | August 25, 2009 11:12 AM
Maybe it is.
Posted by: Glen Davidson | August 25, 2009 11:15 AM
Yes, I, too, thought of the paper that suggests that the appendix isn't lost because losing entails even worse maladaption. But over tens of millions of years, that explanation seems inadequate to me.
For what it's worth, I've long thought the appendix was dicey to use against creationism, especially since the evidence that it is a vestige of anything useful has been so sparse. Better vestigials are platypus and baleen whale teeth (which may function in development, but are clearly vestiges, and fall out before they are weened), and goose flesh among humans (if functional, only very minimally).
The best evidences of "poor design," however, involve adaptation to a new way of living, where an Archaeopteryx is adapted to flight, but partially held back by its preceding terrestrial form. Then it's not a matter of "deterioration" (it isn't with platypus and baleen whale teeth, either, but the pseudoscientists will try to claim it), nor is it a matter of any known method of achieving "poor design," it is solely due to evolution.
Glen D
http://tinyurl.com/mxaa3p
Posted by: Chris Caprette | August 25, 2009 11:29 AM
I still like the saying that if there was a designer it was a civil engineer because only a civil engineer would run a sewer through a recreational area. Other, less humorous examples (from vertebrates) that come to mind are the position of the glottis (which leads to choking necessitating an epiglottis and complex muscular control) and the inverted retina, neither of which makes sense except in light of evolution.Posted by: MK | August 25, 2009 11:31 AM
How come the imbecile bobs without any scientific training started giving "opinions" on scientific matters? This is not for you dudes, just as cows are not supposed to opine on how to make burgers.
Posted by: Heather F. Smith | August 25, 2009 11:32 AM
Thanks for your great summary of this paper, PZ! I agree that molecular and developmental data would contribute to a more thorough understanding of this interesting structure.
I just want to point out that one of the arguments behind the appendix evolving partially or entirely as a safe-house for commensal bacteria is the fact that in the few nonhuman taxa that have been evaluated such, there is also a biofilm present in the appendix, including the rat in our study and the koala. Yes, it could still be a case of convergence, and the biofilm could be secondary to the appendix’s original function (whatever that might have been). However, it seems less likely to me that this is the case given that every taxon evaluated thus far (admittedly an extremely small number) shares the trait that indicates this function. Plus, the outgroup to mammals in our study, the frog, exhibits a concentrated biofilm in its proximal large bowel suggesting that the immunological function of this portion of the large intestine may have been present in vertebrate evolution since before the origin of mammals, and before the appendix itself. However, frogs have short and quite simple large intestines (they’re insectivorous), and while I’m not an expert in amphibian anatomy by any means, I could see why there would be less of a need for a protective reservoir of bacteria in a simpler gut. I agree that just the fact that the structure has been retained for 80 million years (whether or not you buy that argument) is not sufficient evidence of selection for a function; however, the fact that the structure may still perform the same function for which it initially evolved supports the argument for it being selected for. The appendix is found variably or is even absent in several primate taxa, without any apparent patterning of this trend by dietary category or behavior. To me, another interesting question is why these particular primates lack an appendix while the rest possess them. However, it also demonstrates that the appendix is not always maintained in taxa whose ancestors had them.
Right. So, more molecular data and more histological sections of appendices in a wider range of taxa, and we’ll get to the bottom of this. Any volunteers?
Posted by: Galbinus_Caeli | August 25, 2009 11:33 AM
Thank you for this. As a very recent appendectomy patient (still bandaged), I find this discussion very interesting.
Posted by: Runciblius | August 25, 2009 11:34 AM
The last time this subject came up (several months ago,
I think) it seemed that other primates had larger
cecum/appendix complexes in relation to how large a
percentage of their diet consisted of leaves. This
would, I guess, be the 'fermentation chamber' PZ
mentioned. Does the appendix have a distinct function
in those species which eat lots of leaves?
Posted by: jj | August 25, 2009 11:42 AM
Earth?Posted by: jj | August 25, 2009 11:48 AM
Good review, and it sounds like the authors actually did a good job - they have written a paper, with what seems to be a decent analysis, which have in turn prompted more questions! The more we find out, the more questions we have, leads to more information. That's what I love about science, critical thinking!
Posted by: Heather F. Smith | August 25, 2009 11:51 AM
Runciblius,
The appendix appears to be acting as a fermentation chamber in species that having a very wide voluminous appendix (rabbits, koalas); however, it's too small in most primates to do much real fermentation. You're remebering correctly about the cecum, though. Highly folivorous (leaf-eating) primate species tend to have either enlarged ceca or stomachs to ferment the otherwise indigestive cellulose found in plant cell walls.
There does seem to be a trend within primates that those with larger ceca have higher frequencies of appendices. It's unclear what might cause this trend, and it doesn't seem to characterize other nonprimate species.
Posted by: me | August 25, 2009 11:52 AM
what if it's one of those stupid mutations that, because its on the inside, no one could see, but the original organisms that sprouted them were a little hotter on the outside so they had more offspring and here we are with appendices? maybe that's why our livers are on 1 side, or why i have a deviated septum... i wont get all "the lord works in mysterious ways" but he sure seems clumsy sometimes with this life-form junk... :) and if it isnt about devine intervention (i'm agnostic by the way) i wouldnt expect any perfection from evolution. if it's a slow improvement with everything being useful, i would have stronger fingernails, right? :-)
Posted by: Epinephrine | August 25, 2009 11:53 AM
@ Heather F. Smith
Thank you... from pedants everywhere
Posted by: Knockgoats | August 25, 2009 11:53 AM
BTW, does the paper have an appendix?
Posted by: mikecbraun | August 25, 2009 12:01 PM
Maybe it is the remnants of a part of the digestive system that was needed with our ancestors' more plant-based diet? Just conjecture.
Posted by: MikeM | August 25, 2009 12:15 PM
It took a lot of guts to write this, PZ.
When I had my appendix taken out a few years ago, the surgeon told me they'd removed a healthy appendix. Further testing in their lab showed that I had actually survived a bout of appendicitis at some point in the past, even though I don't remember ever having any pain.
But that's when they discovered my "thickened ileum" -- Crohn's disease.
So, PZ, if there are appendixes, why is there still Crohn's disease? Huh? Hah, I got you on that one.
Finally off prednisone. Man, run away from that drug if you can (but don't take my advice on that one...).
Posted by: devbiologist | August 25, 2009 12:22 PM
Thanks for the great post, PZ! You've fed my brain this morning.
Posted by: Brock | August 25, 2009 12:30 PM
other mammalian groups that lack an appendix to switch off appendix development were identical, that would suggest that the last common ancestor of the eutheria had that mechanismI think that first use of "appendix" should be "mechanism". Fifth-to-last paragraph, last sentence.
Posted by: wÒÓ† | August 25, 2009 12:35 PM
Answers.
Caecum and ye shall find 'em.
Posted by: Aaron | August 25, 2009 12:41 PM
If creationists try to claim this paper proves something they've been claiming all along, then they didn't read it and didn't understand it — it'll be a clear case of circular illogic.
Right...because that's stopped them before.
Honestly, I expect they'd be more likely to cite the article written ABOUT this publication, and just fabricate what the publication talks about. Being disproven publically has never stopped them before from repeating it to their scientifically illiterate constituency.
Remember the "Darwin was wrong" debacle? And the recent NatGeo "Evolution thrown on its end" title?
Posted by: Jennifer B. Phillips | August 25, 2009 12:41 PM
Knockgoats@16: Indeed! Legend has it that
...or so I've heard tell.Stogoe@17: *Sigh* You just had to go and bring up "Free Will", didn't you? That practically guarantees a creationist infestation. Thanks, man. Thanks a LOT. *eyeroll*
PZ: I agree, it seems premature to propose an ancestral state from these data alone, and I second your call for a more genetically driven exploration of appendix development. Looking at linkage could also be informative. Maybe the appendix building genes are just along for the ride with something more crucial to gut development in these particular mammals?
Posted by: Ryan Egesdahl | August 25, 2009 12:46 PM
Heather F. Smith #23
IANAB (I am not a biologist), but from a logical standpoint this argument leaves me unconvinced. The problem is that the apparent function of a morphological characteristic cannot be used to reason its selectivity; it's like trying to reason the necessity of religion by its apparent benefit. The data suggests that the appendix has an apparent benefit for those organisms that retain it (whatever that benefit may be) but nothing more. If we are to accept that the appendix is retained as anything more than a neutral adaptation, we would need data that suggests differential selection, and the only current way of doing that is by molecular analysis.
I would agree that this paper is interesting, but it is only preliminary and suggests further work to do; there are no conclusions that can be made by it, suggestive or otherwise. We should investigate more to find out the hows and whys and whether the apparent function of the appendix is as convincing upon more detailed analysis, just as you have suggested, but without any encumbrance of previous conclusions.
Posted by: Akiko | August 25, 2009 12:53 PM
The appendix as a back up reservoir for lost gut flora is ludicrous. Just as you said, then millions of people would not be dead from diarrhea, the number one killer of children under the age of 2 years. I think the biggest clue as to the presence of an appendix is why does it so often become inflamed? Perhaps the mechanism behind this mysterious inflammation could yield clues. Is the appendix trying to start functioning in some capacity and then becomes inflamed? Is is vulnerable to certain bacteria? I would also like to see some gene sequencing work in this area. I think the appendix has been written off for too long as useless therefore unimportant enough to study. A neglected mystery in our bodies.
Posted by: Rick | August 25, 2009 1:04 PM
Great post doc... I learned a little something about the mammalian gut! Interesting stuff.
Posted by: Laura | August 25, 2009 1:05 PM
This was maybe not the best article to read on my lunch break.
Mmm... chyme...
Posted by: Stripe
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August 25, 2009 1:05 PM
I'm impressed! You've refuted every argument before it's even been made! How truly astounding you are!
Perhaps you'll give a creationist a little shot at trying anyway. What can it hurt given that you've already won?
It's my opinion that evolutionists get their assumptions horribly wrong. Take this one:
That's stupid. The most parsimonious explanation is that the ancestral state of mammals was to have a well developed appendix. With a near universal change in diet so came a tendency to not need the full organ. The YEC trump card over evolution is always that it is far easier for a biological feature to degrade, become smaller or lose function than it is for the same feature to upgrade, grow larger or add functionality.
How'd I do?
Posted by: TiG | August 25, 2009 1:06 PM
MikeM - Congrats on being prednisone-free! I too have the dreaded Crohn's and this article was fascinating to me. I might be a weirdo since you might say I devour anything regarding the digestive system. I've always wondered what appendices were for, since mine was taken out so long ago and as far as I know nothing is different. I'd venture to say vestigal at best, but I'll look forward to more sciency-types figuring it out!! =)
Posted by: Peter G | August 25, 2009 1:06 PM
The fact that a burst appendix can take you out of the evolutionary sweepstakes suggest to me that it does indeed have some function. I've always thought the idea that it was our own on board petri dish to be a reasonable hypothesis but if not that then some other function will doubtless be discovered. As a bacterial culture dish it may also serve as part of the immune system by cultivating harmful bacteria in a controlled environment where the body can deal with it immunologically speaking. In any event there must be some useful function or it would have been selected against.
Posted by: uncle frogy | August 25, 2009 1:11 PM
as one who has had some extreme bouts of diverticulitis I find all discussions about digestion and diet interesting and compelling. there seems to be much we do not know and I await more results. thanks for your analysis, AOL had a "head line" piece this morning that said vary little
Posted by: Dr.Woody
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August 25, 2009 1:12 PM
Does the fact that 70% or so of both rodents and simians manifest this development suggest the possibility of a specific common ancestor?
Humans are very ratlike under certain circumstances (and rats behave a lot like humans, commonly, too)...
just askin...i got no rat in this race...
Posted by: Ryan Egesdahl | August 25, 2009 1:15 PM
Stripe #43:
I like that - "trump card". Because it is clearly much more likely that there was some "proto-mammal" that had a well-developed appendix that only changed over time than having something that grew from a single genetic mutation into the phenotypic variation we see now. I can see where someone might be tempted by that right up until the "well-developed" part; then we have to ask where that appendix came from. Invariably, the answer is "Goddidit" and there ends the questions. Creationism in any form kills scientific investigation because there is always some point where a creationist will stop investigating and give an unsatisfactory knee-jerk answer.
I think you demonstrated the creationist position well enough, but for some reason I remain unconvinced by it. How strange is it that I demand evidence?Posted by: Knockgoats | August 25, 2009 1:18 PM
How'd I do - Stripe
Badly. You failed to make a distinction between the authors' interpretation of the evidence, and PZ's.
Posted by: Ryan Egesdahl | August 25, 2009 1:25 PM
Peter G #45:
Not necessarily. Neutral adaptations are retained all the time. If the appendix has "no function", then it could be retained. In general, maladaptive and adaptive traits have a selection pressure tied to survivability, which must also be tied to reproductivity. In the case of the appendix - well, as long as there isn't a reason why something only kills large numbers of people with one before reproduction, there wouldn't be a reason for it to be selected out.
Yes, I know this is an amateurish view of evolution, but IANAB.
Posted by: Knockgoats | August 25, 2009 1:27 PM
The YEC trump card over evolution is always that it is far easier for a biological feature to degrade, become smaller or lose function than it is for the same feature to upgrade, grow larger or add functionality. - Stripe
While the evolutionist trump card over YEC is that it is supported by reams of evidence from all branches of biology, geology and paleontology, while creationism is supported by quote-mining and making stuff up.
Posted by: Celtic_Evolution | August 25, 2009 1:27 PM
I'm impressed! You've managed to confuse the meaning of "every" with "one". How truly astounding you are!
Ahhh... I get it... that was meant to be sarcastic. Good thing I read it twice or I would have just assumed you were being an asshole.
Well... you put the first sentence in the wrong place... OH... and of course you forgot to back up anything you're claiming with any actual evidence... but otherwise it's ordinarily unimpressive.
Posted by: MikeM | August 25, 2009 1:30 PM
TiG @44: Thanks. I really didn't realize how hard prednisone is on the body.
My GE doctor worked hard to convince me to switch to Humira, which I have done. Didn't want to give myself shots. After two 4-day stays in the hospital this year, I was convinced. At $700/shot, I'm glad I'm not paying for it.
Crohns hurts. I sometimes wonder, though, if the unappreciated appendicitis I had who-knows-when didn't lead to my Crohns. If there is some validity to the theory that, somehow, the appendix serves to replenish digestive system bacteria, you'd think there might be some connection.
Diabetes, cataracts, bone-thinning, blood vessel weakening... Yes, indeed, prednisone has it all. Oh well, at least it's cheap.
Posted by: F | August 25, 2009 1:34 PM
Awesome. Thanks for the opinion along with actual content from that paper. I've only seen Science Daily type synopses so far.
Posted by: amphiox | August 25, 2009 1:43 PM
#40: Since the putative function of the appendix is the replenishment of gut flora after a diarrheal illness, you cannot fairly use diarrheal mortality as an argument against it. The appendix may well do nothing at all to protect against diarrheal illness, and still maintain a role in repopulating the gut flora after recovery by other means.
When we're talking about the commensal gut flora, I think we also need to consider the possibility that it was the gut flora themselves that evolved to exploit the appendix/cecum as an environment where they could establish stable biofilms, after the appendix appeared for other reasons.
The intestinal tract has a very wide variety of microenvironments and structures within it that can provide a haven for commensal gut flora, and I would be very surprised if the appendix turned out to be the only reservoir of biological importance.
Appendicitis is not an unreasonable candidate for a negative selection pressure that resulted in the loss of a putative primitive appendix in the majority of mammalian lineages.
Does anyone out there know if ruminants have large cecums? Just thinking that since they have multi-chambered stomachs that are used as fermentation chambers, a large cecum might be redundant for them, and so not evolve in that lineage. If so, in that lineage, the appendix may have been lost simply as a incidental consequence of shrinkage of the cecum?
Posted by: Anonymous | August 25, 2009 1:47 PM
What is the purpose of hymens? How did they come to be?
Posted by: AdamK | August 25, 2009 1:48 PM
@ Heather Smith
Danger! You are entering an inadvertent puns area! Please reduce the speed of your discourse! Have a nice day.
Posted by: Galbinus_Caeli | August 25, 2009 1:48 PM
A number of commentators have suggested that the tendency for the appendix to become septic could be counter evolutionary. As a counterpoint, note that most cases of appendicitis affect adults over the age of thirty. Until very recently most people were done with most of their reproduction by age thirty. If you aren't having kids, evolution doesn't have much use for you.
Posted by: amphiox | August 25, 2009 1:49 PM
"The YEC trump card over evolution is always that it is far easier for a biological feature to degrade, become smaller or lose function than it is for the same feature to upgrade, grow larger or add functionality." - Stripe
How so? Evolution readily accommodates the loss and degradation of function.
OTOH, why should an all-powerful creator design features susceptible to degradation over time, why would an all-benevolent creator allow features he designed to degrade over time, and why would an all-knowing creator not foresee that some features are prone to degradation over time and take appropriate countermeasures?
Posted by: Eamon Knight | August 25, 2009 1:50 PM
Diabetes, cataracts, bone-thinning, blood vessel weakening... Yes, indeed, prednisone has it all. Oh well, at least it's cheap.
Oh great, I've got a cat on the stuff at the moment, as the latest in a months-long series of problems and therapies. But as you say, at least it's cheap (especially compared to the antibiotics he was previously on).
Posted by: Nerd of Redhead, OM
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August 25, 2009 1:52 PM
Nice explanation PZ. I too, would be interested in seeing how the appendix is formed, and what other control genes it is tied to in the genome.
Posted by: Chiroptera | August 25, 2009 1:55 PM
Stripe, #43: The YEC trump card over evolution is always that it is far easier for a biological feature to degrade, become smaller or lose function than it is for the same feature to upgrade, grow larger or add functionality.
The evolution trump card over YEC is how it explains the pattern of groups that have an appendix -- they fit nicely onto the phylogenetic tree.
How'd I do?
Posted by: Eamon Knight | August 25, 2009 1:57 PM
A number of commentators have suggested that the tendency for the appendix to become septic could be counter evolutionary. As a counterpoint, note that most cases of appendicitis affect adults over the age of thirty.
And perhaps just as important, it's also rarer in those with high-fiber diets (or so I've heard) -- which most of the human race ate, until very recently (and still eats, if they aren't rich enough to afford an unhealthy Western diet).
Posted by: amphiox | August 25, 2009 1:58 PM
#2: Let's not be too hard on the poor medical students. S. aureus is ubiquitous enough that they needn't have been the vector. :-)
#53: There is a documented link between appendicitis and Crohn's disease, but it is very small. But it is unclear how many of these appendicitis cases were actually early manifestations of Crohn's, given how RLQ pain is a common symptom of Crohn's.
#58: The incidence of appendicitis in children, and the death rate from appendicitis in children prior to modern surgery, is plenty high enough, I think, to invalidate that argument. What we don't know is how long in our evolutionary history have we been subject to the current appendicitis rate. If, as some have suggested, modern diets play a big role in increasing the risk of appendicitis (with presumably traditional hunter-gatherer diets not contributing a very high risk), then the scourge of appendicitis may have only dated to historical times, perhaps only as far back as the invention of farming, in which case it may simply be that there had not been enough time for evolution to completely eliminate the appendix before modern surgery came along and alleviated (mostly if not completely) that negative selection pressure.
Posted by: amphiox | August 25, 2009 2:01 PM
Predisone is a powerful drug, with many side-effects. It is also a very effective drug.
If you should need it or benefit from it you should not be afraid to take it. It is, as always, a matter of balancing the risks of the side effects with the likelihood of the benefits accrued.
Posted by: Dania
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August 25, 2009 2:03 PM
The 'magic man in the sky did it' explanation is so much more parsimonious, isn't it?
Posted by: PZ Myers
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August 25, 2009 2:05 PM
Hey, this is personal! I had acute appendicitis when I was 8 or 9 -- if it weren't for the emergency surgery I received, I'd be dead.
Posted by: Heather F. Smith | August 25, 2009 2:22 PM
Like PZ, I also had my appendix removed. I wonder if my interest in the topic is partially driven by appendix envy.
Posted by: Tulse | August 25, 2009 2:27 PM
It's all due to The Fall, silly! Everything got fucked up and degraded by The Fall. If it weren't for The Fall we'd be livin' disease-free forever with our coconut-eating Tyrannosaur buddies!
Posted by: Peter G | August 25, 2009 2:36 PM
Ryan @50. I think you missed my point. It isn't a neutral adaptation if it serves no function but its' presence kills a significant number of people who have it.
Posted by: Brownian, Most Vicious & Petty of Pharyngulites
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August 25, 2009 2:47 PM
Yeah. Stripe whined,
What do clowns like you have besides "Goddidit" and "X was perfect until the Fall. Every wrong thing is because of the Fall. Did we mention the Fall?" (Oh, and "We hate gays")? Is there more to refute? Every line of 'evidence' besides blanket denial you crooks manufacture have been refuted. Dembski's '3 little engines' anyone?
The fact that you can parrot the word 'parsimonious' doesn't mean you know what it is, idiot. Parsimony requires evidence for context. It would be parsimonious if we saw older organisms with more, well-developed appendices, but we don't. We see the opposite. We see exactly what evolution would predict and the exact opposite of what YEC predicts.
Go on, then. Start denying the evidence. It's all you little fucking liars have.
You waste valuable time and resources with your stupidity. You're parasites and leeches who prey on the young, the gullible, and the uneducated, and you bite the hands of those that feed you, such as the scientists whose real research saves your pathetic, miserable little lives.
The points you've argued will be refuted numerous times here on this blog with multiple lines of evidence. You will ignore the evidence. You will lie. What else is there for you to do? You will waste time.
And you ask what the harm is? You rotten, selfish twit.
Posted by: Rebekah | August 25, 2009 2:55 PM
#40: "...then millions of people would not be dead from diarrhea, the number one killer of children under the age of 2 years."
As someone who studies diarrheal disease, cholera namely, I can tell you that these people do not die from the failure of bacterial recolonization, but rather from massive dehydration and/or damage to the epithelium. Labeling people's studies as "ludicrous" based on incorrect assumptions is juvenile and irresponsible.
Posted by: Richard Wolford | August 25, 2009 2:59 PM
This is off topic, but I saw a couple of folks having a discussion about Crohn's Disease. I have a related disease, ankylosing spondylitis. Any bloggers here, preferably doctors, have any posts about this disease? I'm still researching what I have and generally like everyone who posts here, so thought I'd ask.
Oh, and I still have my appendix. This was another great post, I always learn when I come here.
Posted by: jb | August 25, 2009 3:09 PM
@67-68:
My family is really good at catching the symptoms of appendicitis... mostly because none of us have one post-childhood.
Posted by: Sid Schwab | August 25, 2009 3:12 PM
As a surgeon who's taken out, give or take, a thousand of the little critters I remain unconvinced of any significant function other than to have put some butter on my bread.
I've seen people with (presumably) congenital absence of the appendix; others with merely a fibrous stripe where the appendix should be. (The latter might be due to undiagnosed appendicitis which resolved without treatment. Who knows?)
The paper presents an interesting hypothesis, but no evidence for it. Many papers have compared, retrospectively, appendectomized patients to "normal" ones and have no difference in acquisition of future problems. (One paper suggested a higher incidence of Crohn's disease, which I question because there's a number of people with Crohn's who get their appendices removed via a wrong diagnosis. Another suggested a LOWER incidence of ulcerative colitis.) Over all, there's not been significant CLINICAL evidence of adverse effect of appendectomy, long term.
It seems to me the ideal study to test the hypothesis of the paper would be random selection of people to be divided into two groups: one gets the appendix removed, the other, not. Then give them both a diarrheal illness (well after recovery from the operation), and test, by collecting stool samples, the rate of repopulation. Any takers?
Posted by: Sven DIMilo | August 25, 2009 3:12 PM
must...not...bring up...the word......"data"...
Posted by: amphiox | August 25, 2009 3:20 PM
#69:
But. . . but. . .
An all-powerful creator surely could have designed The Fall. An all-knowing creator certainly would have foreseen The Fall.
But an all-benevolent creator allowing The Fall?
It is here that my frail attempts at comprehending theology crash and burn, every time.
Posted by: LKL | August 25, 2009 3:21 PM
To combine the premises of the paper and PZ, *if* the appendix evolved as a reservoir for helpful gut bacteria, and *if* it is an ancestral feature, then it seems likely that taxa for which hindgut fermentation is important would be the least likely to have secondarily lost their appendixes. Given that several large hindgut fermenters (horses, elephants, etc) are among the taxa without appendixes, one of those premises must be incorrect; either the appendix did not evolve for that function, or it has evolved independently in several lineages.
I don't know enough about taxonomy and the relevant lineage's diets to determine if those with appendixes had hindgut fermentation (or at least folivory) as an ancestral condition (which might support the authors' premise).
At least we seem to be leaving behind the old, 'the appendix has GALT! Therefore it must be beneficial!' canard.
Posted by: amphiox | August 25, 2009 3:24 PM
#75: Maybe we wouldn't have to go with the diarrheal disease route. A good dose of oral antibiotics should do pretty much the same trick.
Or maybe we canvas hospital GI wards to recruit patients to participate in a study after they recover from their diarrheal illness?
I have a feeling getting both funding and ethics approval for these types of projects is going to be a bit tricky.
Posted by: amphiox | August 25, 2009 3:27 PM
#73: Hmm. Crohn's and Ulcerative colitis are inflammatory bowel diseases, but ankylosing spondylitis isn't. I'm not sure you can say that they are all that related, other than the fact that they all may have some autoimmune component.
But then again, rheumatology and immunology are not my areas of specialty.
Posted by: LKL | August 25, 2009 3:30 PM
Do other (non-human or non-primate) taxa ever die of appendicitis? And does some of the human variation (large vs. small appendix) have an advantage over the rest in terms of frequency of appendicitis or positive resolution of appendicitis?
Is there a difference in recovery time after cholera, or other diarrheal illness, for those who have no appendix vs. those who do?
Posted by: mikecbraun | August 25, 2009 3:32 PM
Is the appendix's tendency to become inflamed and/or harm the individual really relevant in the saga of the appendix? It does not seem to impact the debate about function or lack thereof historically--tonsils can do the same, as can gall bladders, hearts, kidneys, livers, etc. This just may be an environmental stress reaction or consequence of our lifestyle, as amphiox noted @ #64, and may be a red herring. The tailbone was not always just for landing on during drunken sledding excursions, and the fact that now it's just a nub to land hard on says nothing of its former and current usefulness or uselessness. Does this make any sense, or is it just babble?
Posted by: Tulse | August 25, 2009 3:35 PM
It's all about free will, dude. Even though He might have known what would happen, could have forseen it all, even made it all, God couldn't intervene and still give us free will. You know, just like because your toddler has free will you can't intervene if he runs out in the street. It sucks, but what's a loving parent who believes in free will to do?
Posted by: Ryan Egesdahl | August 25, 2009 3:39 PM
Peter G #70:
No, I caught it. I was simply making the statement that adaptivity is tied to reproduction. If most people who have a trait are only killed by it after reproducing (as is the case with an appendix), then the trait is not maladaptive for the purposes of selection. There's also data to show that diet has much to do with appendicitis anyway - that the modern Western diet seems to contribute much to its incidence; more agrarian societies tend to have much less occurrence of death by appendicitis. (I wish I could find the data, but I am no longer on a university subscription.)
You are correct in your assessment of appendicitis, but that fact alone does not make the appendix a maladaptive trait. For the purposes of selection, it can be considered essentially neutral unless more research can show otherwise.
Posted by: mokele
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August 25, 2009 3:40 PM
Rather than messing about with genes and such, wouldn't the logical next step be to simply test the functional hypothesis?
Find the a cheap, small, easy-to-work-with species with a well defined appendix & associated bacterial films, get a few hundred, split them into control, appendectomy, sham surgery, and possibly some method to totally remove biofilms (cecal amputation?). Then infect them with some sort of diarheal disease, track their progress, cure them all once they reach a predetermined stage, and chart the rate of bacterial recolonization (as well as other salient variables indicating overall health).
Personally, I find a direct functional test more convincing than anything else. Of course, it'd be a huge pain in the ass, and cost a fair amount, but I'm betting you could write a pretty compelling grant application with what you have so far.
Posted by: amphiox | August 25, 2009 3:42 PM
#83:
Yeah, but my free will is already limited by the fact that there are some things my brain is simply not capable of conceiving of, and hence some choices I can never choose to make.
I cannot comprehend in any meaningful way a probability of one in four quadrillion. I cannot choose to become telepathic. I cannot hold my right elbow in my right hand, no matter how much I might want to choose to do so.
So why couldn't our benevolent creator simply designed us all to be incapable of conceiving of harming other people. It would be such a pitifully minimal limitation on our free will compared to how he has already seen fit to limit us. We would be so much happier and healthier, and we would hardly notice the difference in freedom. We was gipped, man!
Posted by: amphiox | August 25, 2009 3:46 PM
#82: What it does show is that however and whenever appendicitis reached the prevalence in the human population that we observe today, a changing environment results in a trait that may have been formerly neutral or even helpful to one that is detrimental, and another change in the environment subsequently removes the detrimental effect.
It's the stuff evolution is made of.
Posted by: Ryan Egesdahl | August 25, 2009 3:50 PM
mokele #85
The opportunity for unintentional puns on this topic is simply remarkable, isn't it?
Posted by: mikecbraun | August 25, 2009 3:53 PM
I see what you're saying, amphiox. That does not, however, tell us anything about its former function, if any. Maybe it is just a hitchhiker that is expressed with some more important trait at this point. You make (a) good point(s), and it would be interesting to see if there is a trend toward the appendix being done away with, as it were, by evolution, or if it does indeed need to be there in order for something more important to develop or take place (molecular study comes in here again).
Posted by: Peter G | August 25, 2009 4:02 PM
Ryan@84 I would accept your argument completely if appendicitis were generally to occur when humans were past their reproductive years but this is not true. It afflicts all ages of humans and prior to the advent of modern medicine was a common cause of death.
Posted by: Rosie Redfield | August 25, 2009 4:10 PM
Speaking as a microbiologist, it's absurd to postulate that the appendix is needed as a reservoir of bacteria. The numbers of bacteria in our gut are vast (10^13? 10^14?), and even very severe diarrhoeae would leave billions of them in place. Biofilms are notoriously hard to eradicate and there's no need to postulate any special mechanism to preserve them.
Posted by: Peter G | August 25, 2009 4:12 PM
Forgot to add the link. The incidence of appendicitis is highest among adolescents and young adults. http://www.springerlink.com/content/rnrwyur8vu5wymvb/
Posted by: Richard Smith | August 25, 2009 4:20 PM
This is all quite informative. Much moreso than a text I used to have on the subject - somebody'd removed all the pages of extra info at the end of the book.
PS: What's the most common ailment among witches? Crone's disease.
Posted by: MikeM | August 25, 2009 4:23 PM
Short-term use, absolutely. Long-term use, try to avoid it.
I used to just touch a doorframe a little too hard with my forearm, and it would bruise or even bleed. Been off it since April, and this tendency is clearly going away.
Humira is a little scary, too. Read the TB and lymphoma warnings on it. That's why I avoided it for so long, but I couldn't keep going to the emergency room. At some point, the risks became acceptable.
My doctor told me, stay on prednisone long enough, and there is a 100% chance of side-effects. That was good enough for me.
Posted by: Peter G | August 25, 2009 4:26 PM
RR@91 You are correct I think in arguing that it's function is solely to act as a reservoir of recolonizing bacteria although this is possible. It is not well placed to serve this function. It is difficult to imagine a mechanism whereby the appendix could distinguish between "good" and "bad" bacteria. It makes more sense for it to be part of the immune system. It still could be acting as a controlled area of interaction with the immune system and it's location on the exit side makes more sense from the point of view of functionality.
Posted by: Ryan Egesdahl | August 25, 2009 4:28 PM
Peter G #90:
Actually, appendicitis has always affected people aged 30 and over more than any other group, and it seems to have much to do with diet. Even only 60 years ago, it was expected that by that age, a person would already have been married and had a child. Even so, appendicitis was never a major cause of death, however common it was. There is also evidence to show that cultures having a diet consisting of high amounts of fiber have a much reduced incidence of appendicitis in the population. And finally, the rate of appendicitis is decreasing as more people in Western society move to healthier diets.
There simply isn't any evidence to show that the appendix is a maladaptive trait. I'm not saying it couldn't be, but we don't have data to back up such a notion. All the evidence available at this time (to me) suggests that the appendix is a neutral trait.
Posted by: Ryan Egesdahl | August 25, 2009 4:42 PM
Peter G #92
I cannot retrieve that article, since I am no longer on a university account. However, the abstract suggests that the article is more about the rate of misdiagnosis in these cases and that more attention should be paid to improving the accuracy of tests. In any case, the rate of appendicitis cases has been decreasing over the years as popular diet has changed to high-fiber and low-fat. That would render any argument about the incidence of appendicitis being highest within any age range irrelevant without corroborating data that takes diet into account. If that article addresses this issue, I can't tell from the abstract alone.
However, none of the above is relevant to the fact that appendicitis in societies with high-fiber diets (closer to what the diet was thousands of years ago) would seem to have been rare, based on what we now know. That would also mean that appendicitis wouldn't have been a significant adaptive pressure in any respect.
Posted by: amphiox | August 25, 2009 4:44 PM
#96:
A peak incidence beyond the age of peak reproduction does not mean it has no effect on reproduction! Even though most common in the over 30 bracket, appendicitis in children and young adults is plenty common enough to have a selective effect (and the reproductive rates of individuals over age 30, even in hunter-gatherer societies, is high enough for things affecting their mortality to have significant selective effect). Let's also not forget that mortality of individuals over age 30 is believed to have a significant impact on the survival of grandchildren during our species' evolutionary past, and hence is a factor subject to natural selection.
Also, mortality is not the only issue to consider. Appendicitis is associated with infertility in young women. (Although there is some controversy here - the evidence is not clear cut)
Whether the appendix is detrimental (I prefer this to maladaptive), beneficial, or neutral is going to come down to quantifying its varying effects over time, and the magnitude of those effects are going to fluctuate independently of one another over time. Not the easiest thing to do with any reliability.
Posted by: Sven DIMilo | August 25, 2009 5:06 PM
"Chyme" is an excellent Scrabble word.
Posted by: Richard Smith | August 25, 2009 5:16 PM
Due to a rare chemical imbalance in my digestive system, the slurry in my large intestines produces gases even without bacterial activity. I am one of the few that suffers from wind chyme.
Posted by: Peter | August 25, 2009 5:17 PM
I'm not sure how you could say that the article I cited is about misdiagnosis of appendicitis. It is a statistical analysis by age and sex of people who were shown to have life threatening appendicitis and that was 76% of the population studied that were suspected of having it. It is in no way a study of misdiagnosis. The title of the paper is quite enlightening.
Posted by: Richard Smith | August 25, 2009 5:18 PM
BTW, I know it's pronounced with a hard "ch", but at least it works on paper...
Posted by: Peter G | August 25, 2009 5:42 PM
I can't help but wondering Mr Smith, if you have a resonant frequency.
Posted by: Ryan Egesdahl | August 25, 2009 5:44 PM
@amphiox #98: I'm not arguing that anything that occurs after the age of peak reproduction has no effect on reproduction. I'm just arguing that it, in this case, it would cause an insignificant selective pressure. The incidence of appendicitis in hunter-gatherer societies would, by current understanding, have been somewhat rare. The effect of appendicitis on the mortality rate would therefore have produced little or no selective pressure against having an appendix.
I'm also not saying that the appendix doesn't have some function, even if we don't fully know what it is (or isn't). We also don't have any reliable data to suggest that lack of an appendix is either beneficial or detrimental in the long run because we've only removed the appendix to treat illness. But to say that because removal of the appendix does treat an illness that the appendix is a maladaptive trait is fallacious. One does not imply the other.
Posted by: Ryan Egesdahl | August 25, 2009 5:49 PM
Peter #101
Every article is constructed to address a particular point. In this case, the final sentence of the abstract should tell you what they were addressing:
"We suggest this observation deserves attention regarding clinical diagnosis and treatment decision-making for patients with suspected acute appendicitis."
Yes, it's a statistical analysis, but they were looking for something in particular. Without the raw data in your hands, you wouldn't be able to make other inferences.
Posted by: Jamie Gillett | August 25, 2009 5:55 PM
I always enjoy it when you write about science - you are one of the writers that make it interesting and easy to understand.
Posted by: Ken
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August 25, 2009 6:04 PM
Many of you may already be aware, but did you know that if you stretch out a man's small intestine from end to end, that man will die?
Posted by: amphiox | August 25, 2009 6:06 PM
#104: But how do we define "insignificant", and how do we determine when some effect is "significant" or not. Statistical analyses demonstrate that even very, very small selection pressures can, if persisting for long enough, result in enormous ultimate impacts. So the real question is, what is the magnitude of the varying selective pressures upon the appendix, how long have they been in play, and how are they changing with time?
As I said before, I don't like the term "maladaptive". The appendix exists in humans. So either it was at one time (and maybe still) adaptive, or it is contingent and neutral, or it is detrimental but contingent in a manner that has so far preserved it from purifying selection forces (having the formation of the appendix related to developmental regulatory networks critical to some other highly beneficial/essential developmental process that cannot be readily changed would be one example), or it is the whim of a inscrutable creator. I do not know of any other option (sans number 4) that evolutionary theory allows.
I also don't think we should be referring to "hunter-gatherer" societies as the only ones of relevance when considering the evolution of the human appendix. We didn't stop evolving when we invented farming, or industry, or medicine. Selective forces were in play throughout historical time and continue to be in play today, and so things like the modern diet and whatever relationship it might have to appendicitis is relevant to the discussion of its evolution in humans. And do not forget that in the medical literal appendicitis predates modern surgery - it's an old disease, so we have to be careful what we are talking about when we talk about "modern" diets.
As I see it, the facts of medical history make it quite plain that there was a definite period in time where appendicitis was an enormous source of mortality, and the having an appendix was, in that environment, a significant detrimental trait. Detrimental enough that any counterbalancing putative benefit would have had to have been huge, as in Loch Ness Monster huge, as in large enough to have been so obvious that the fact that we did not discover it 200 years ago is good evidence for its non-existence. Admitted this is just my opinion, but that is how I see the evidence as I understand it.
What we don't know is how long this period of negative selection pressure lasted. If it was very brief, spanning only a few centuries or a millennia, say from the widespread adoption of high fat, high starch diets to the development of safe modern appendectomy surgery (and reliable diagnosis of appendicitis), then it is quite reasonable that such a brief period would not have created enough cumulative negative selection pressure to eliminate the appendix from the population. But that doesn't mean that during this period the appendix was not a detrimental trait.
Posted by: Peter G | August 25, 2009 6:13 PM
"This prospective study was performed to investigate epidemiological characteristics in terms of the age- and sex-specific incidence in patients with perforated and nonperforated appendicitis." Doesn't seem to call for much inference to my way of thinking. With regards to the relationship between diet and the incidence of appendicitis there does not appear to be uniform agreement: http://www.bmj.com/cgi/content/abstract/290/6475/1125
Posted by: Heidi | August 25, 2009 6:47 PM
There is something vitally important here that creationists are, intentionally or not, completely missing.
This is how science works. Somebody writes a paper. Then every scientist who reads it can give their opinion on the data. Just like PZ did. Scientists don't just sit there and say "oh, well it's on paper, so it must be true." Scientists continually scrutinize each other's work. What is important in science is not that the person who wrote the paper is right. What is important is whether or not their conclusion is sound. If it needs more work, as this seems to need, they go back and get more data. Then they see where it takes them from there.
And this is precisely why science succeeds, where "this old book says so" utterly fails. Because if someone puts forward a scientific hypothesis, if it's wrong, no one will hesitate to tell them so. Whereas if something in the old book is demonstrably wrong, the answer is "that part is just metaphor," or "that was for a different time." The idea that it's just wrong is apparently unacceptable.
Posted by: beanjavert | August 25, 2009 6:53 PM
I love it when PZ talks about stuff like this; its much more stimulating than talking about creationist bull all the time.
Posted by: truth machine, OM | August 25, 2009 7:16 PM
[distinguishing myself from #56]
How'd I do?
Not bad if you're a Poe who is trying to illustrate the sort of sloppy thinking of creationists that is evident in nearly every line of your post (although even your illogic is no match for that of Akiko, who AFAIK isn't a creationist). For example, you might as well say that the Holocaust denialist trump card is that it would have been far easier to let the Jews go about their business rather than somehow get them into gas chambers and ovens ... despite the fact that, not only does the evidence show that they were put into gas chambers and ovens, but we know how this occurred and why.
Posted by: Ryan Egesdahl | August 25, 2009 7:54 PM
amphiox #108:
Actually, the question is first whether the null hypothesis is valid. The null hypothesis in regards to evolutionary adaptivity is always "the trait in question is neutrally adaptive", and before you can start answering whether any trait is adaptive or maladaptive, you must first determine that it is not neutrally adaptive. We haven't answered that question yet, and the paper before us hasn't either. The term is merely a statement that a trait tends to reduce the capability of an organism to pass its genes on to another generation and nothing more. There is some evidence that this is the case with appendicitis, but none of it is clear because we don't fully understand its causes yet. Also, there is some evidence that the appendix is adaptive if we are to accept the claims of the paper before us. But at no point have we been able to discard the null hypothesis. Modern medicine, diet, and the like are functions of another adaptation humans possess: intelligence. We are only talking about the appendix, so we have to talk about what was before modern conveniences to avoid muddying the waters with irrelevant details. Since we have no time machine, we have to study cultures that exist as close to that type of society as possible and try to work backwards. More to the point, we don't know what the mortality or morbidity rates were before modern medicine and modern diets. Remember, it was only relatively recently that we learned that gout has almost nothing to do with "unhealthy living". No matter how old a disease is, we can't make assumptions with historical data we do not have. As stated before, the evidence to back up this position does not exist. We also cannot look at history to find the data because we have no independent verification of the facts behind any symptoms or diagnoses - largely due to medical practices that did not exist at the time. Yes, but I am talking about right now, in the context of this paper. What it was in the past is not relevant.
That's because what you quoted is so general as not to propose a question. When you're looking at why a study was done, you need more than a simple overview statement. The last sentence of the abstract presents the question to be answered. I never said there was; however, that article was written in 1985. For perspective, even a biology class is generally considered obsolete after two years. The claims the authors of that paper make may still be valid (there is a 2008 article that references it), but I would be surprised if the conversation on this topic had ended there. Besides which, lack of agreement about facts does not change the nature of those facts. I can concede that diet may not be the only explanation for appendicitis - or even an explanation, but we still don't know what does cause appendicitis in the first place. All we have are correlational data.Peter G #109:
Also, the paper you reference is only relevant to the discussion in a peripheral sense. What is at issue is what may have been different as to the function of the appendix that may or may not be true today. I am only presenting possible counterarguments to show what is not known about that function, nothing more. As I said to amphiox, we haven't found a way to discard the null hypothesis - the research you provide would be highly speculative in determining what evolutionary pressures may or may not have contributed to the retention of vestigial organs simply due to lack of relevance. We need more data.
Posted by: Rorschach | August 25, 2009 9:34 PM
Whatever the evolutionary advantage is that kept the appendix around for 80 million years had better be good, because an infected appendix sure means death for that particular animal.
So really, an appendix in a world without surgeons is probably not what you want.
To the question of whether the appendix was specifically selected for, I'd go with a maybe, but not likely.
Posted by: Rorschach | August 25, 2009 9:37 PM
That should read : "without surgeons or antibiotics" in my 114.
Posted by: amphiox | August 25, 2009 9:47 PM
#113: Well, if we're going to talk about right now, then we have very good evidence on the magnitude of the detriment of the appendix. We know what the current rate of appendicitis is, we know what the likelihood of rupture if untreated is, we know what the likelihood of misdiagnosis is, we know the post-appendiceal rupture infertility rates in women, we know the outcome of surgery, and we know the complication rates of surgery.
This basically adds up to a small, but definite detriment, which is essentially only small because surgery has advanced to the point where it is relatively safe (but not 100% so, and it never will be). The uncertainties on the detriment of the appendix are all historical. Limiting ourselves to the here and now, we know pretty much exactly how detrimental the appendix is, right now.
What we don't know is what the magnitude of benefit the appendix gives to humans right now. How important is recolonization of our commensal gut flora in modern societies where diarrheal illnesses are rare thanks to sanitation? What role does commensal gut flora play in our health and survival right now? If it does turn out to have some relation to inflammatory bowel disease, how much of an association is it, and how much does IBD reduce an individual's reproductive success, in a modern world with advanced medical treatment?
What we have is very solid evidence pertaining to the magnitude of the detriment, and essentially almost no idea at all as to the magnitude of the potential benefit, if it even exists at all.
So you can either say that we do not know enough to make any informed comment at all about the benefit/detriment/neutrality of the human appendix right now, or we can say that given very good evidence of detriment, and no clear idea yet of any putative benefit, but with available studies demonstrating no statistical significant differences over time between people with and without appendices setting an lower limit to the detection threshold on how big that benefit can possibly be (or else these studies would have found something), the proper provisional hypothesis is that the appendix is detrimental at the current moment in time in humans, pending further data.
Posted by: Fil | August 25, 2009 9:50 PM
Nice article PZ, I enjoyed reading the second installment. It struck me what an odd grouping of animals retain (or develop) an appendix and what don't.
"That's interesting: the only groups that have an appendix are the Glires (rodents and rabbits), primates, monotremes, and some marsupials."
One wonders, is there perchance anything else linking these groups that could explain them sharing an appendix, apart from what you have already alluded to? If the little tadger is from a common ancestor, it's a fair way back to link simians and echidnas say....and a long way apart too.
On a personal note, Mrs Fil was living in a remote West coast town here as a preschooler (her dad was the town doctor, recently graduated) she developed acute appendicitis and was "rushed" to hospital on the "ABT" steam train...a tiny narrow-gauge rack and pinion hill climber. Once decayed but now restored, it's a tourist's delight, a journey through fabulous wilderness.
http://www.westcoastwildernessrailway.com.au/history.asp
Posted by: anaxagoras | August 25, 2009 10:11 PM
In response to varied posts:
-- Whether vestigial or not, selected-for or not... the idea that the appendix has a function now in us is, well, cool. :)
-- As to the reasoning that the appendix probably doesn't have the hypothesized function because many people do die of diarrhea (e.g. cholera), especially children--how many more would die if they didn't have appendices? Also, the immune systems of 2 year old children and adults are definitely NOT equivalent, and the hypothesized function is connected with immune function, so you would expect it to not work as well in young children.
-- Someone said that the lack of difference in health and survival of people with and without appendices argues against the hypothesized function. However, people with access to modern medicine to get their appendices removed when necessary will probably also have access to modern medicine and proper sanitation to mitigate morbidity from cholera and other diarrheal diseases (not to mention that people without modern medicine or sanitation are usually co-infected with other things they would have to fight to survive after they survived the diarrheal event).
Posted by: John Morales | August 25, 2009 10:18 PM
anaxagoras @118,
As I understand it, the main causes of death from diarrhea are dehydration and loss of elecrolytes, not the loss of gut flora. If so, that is a spurious reason.
Posted by: Ryan Egesdahl | August 25, 2009 10:21 PM
amphiox #116:
Remember, we have to discount the effects of modern medicine and culture on the data because we are looking at the function of the appendix itself. To do that, we have to look at historical trends. Just because we are looking at the present does not mean we look only at the present.
Yes, I know it seems I am going back and forth on this, but I'm trying to point out that historical data matters to this in the sense that we have to know what the contributions of modern culture are to appendicitis in order to estimate its impact in an evolutionary sense. What we cannot do is to talk only about history and ignore the present.
We have no solid evidence regarding specifically the appendix and its function. What we have is a measure of the efficacy of modern medicine in treating its ailments. In order to understand the potential detriment of possessing an appendix, we have to know what the mechanism(s) of appendicitis is (are) and what the effect of modern culture and medicine are in treating it.For clarity, imagine you have tonsillitis. One might be persuaded that the tonsils are vestigial and should be removed in the healthy adult without concern - and that idea has been presented before. It's only recently that the tonsils have been identified as an immune repository, or a place where the body traps infection in order to develop an immune response before global systemic infection. The same thing is happening with the appendix: because we understand the problems of the appendix much more than its benefits, we assume that it is "useless" and discount its role in the body. It may very well be the case that the appendix is a maladaptive trait that we have overcome with modern medicine, but we don't know enough to make that determination.
Similarly, we could say that either or both of the appendix and the tonsils are maladaptive with respect to modern society (medicine, diet, culture, sanitation, etc.), but that isn't relevant to this discussion.
We can say no such thing because we only understand its ailments, and not very well. We understand essentially none of the benefits of the appendix; the paper in discussed in this post only points to a potential line of investigation. For that matter, the appendix may only be a maladaptive trait with respect to modern civilization, and I could believe that position with the proper data to support it, but it isn't relevant to this discussion.And the proper null hypothesis is that a trait is neutral because it is the general case: most new traits in species are neutral phenotypic changes. Environment largely determines the selective pressure of that trait. Since we do not understand the environment surrounding the selective pressure on the appendix, we have to limit ourselves to the most general view the evidence allows.
Posted by: Rorschach | August 25, 2009 10:23 PM
John M @ 119,
I have a problem with this biofilm-restoration of gut flora argument exactly because of that.
With severe diarrhoea, you die from dehydration, subsequent kidney failure etc, and loss of electrolytes, not from lack of restoration of gut flora if you happen to not have an appendix.
Posted by: anaxagoras | August 25, 2009 10:23 PM
Heather Smith (#23) said:
"I just want to point out that one of the arguments behind the appendix evolving partially or entirely as a safe-house for commensal bacteria is the fact that in the few nonhuman taxa that have been evaluated such, there is also a biofilm present in the appendix...."
I remember when I first started hearing about biofilms, scientists who study them were finding them in all sorts of places, that biofilms are pretty ubiquitous in the environment. (Kinda scary to think about... could lead a person to wash hands 50 times a day...) Also I've been told that a lot of the areas inside the body that are supposed to be "sterile", according to the textbooks, really aren't--we just don't have a good understanding of the populations of the microflora that normally inhabit us. This makes me wonder:
Where in the human body have biologists looked for biofilms and NOT found them? How remarkable is it that there are biofilms in the appendix?
Posted by: Ryan Egesdahl | August 25, 2009 10:24 PM
That should read that the most general view is the most specific that the evidence allows. Sorry for the confusion.
Posted by: Peter G | August 25, 2009 10:24 PM
"For perspective, even a biology class is generally considered obsolete after two years." Remind me again Ryan:when did Darwin write the Origin of Species. That must be really out of date and unworthy of citation. Perhaps you'll be kind enough to offer a single link in support of your arguments so I'll have an equal opportunity to pretend that it doesn't say what it says in black and white.
Posted by: anaxagoras | August 25, 2009 10:33 PM
Rorschach (#121)
"With severe diarrhoea, you die from dehydration, subsequent kidney failure etc, and loss of electrolytes, not from lack of restoration of gut flora if you happen to not have an appendix."
People who live without modern sanitation are usually co-infected with lots of different things. The appendix wouldn't help someone survive one bout of cholera. The issue would be the health status of the person who has just survived severe diarrhea, how well they would be able to resist the next punch. Without the usual complement of friendly bacteria in the gut it compromises the ability to deal with the next nasty bug, at least compared with a healthy individual.
Posted by: Ryan Egesdahl | August 25, 2009 10:38 PM
Peter G #124:
Please. You don't need to be rude to get your point across. In any case, your rebuttal is irrelevant, as I did not say the article is unworthy of citation. I have cited years-old articles before when relevant. You, however, did not "cite" an article so much as referenced it in its entirety without the context of applicability. If you want to say the article you referenced is applicable, despite its date, you'll have to show where its claims are still supported and discredited in current discourse.
Besides which, you are making the claims here, not me. I've proposed potentialities to you as problems in reasoning for you to overcome in presenting your argument, but you may also note that I specifically stated my willingness to accept that those potentialities may be unsupported in literature. In reference to the 1985 article you presented, I stated my acceptance of the proposition that there may be alternative causes of appendicitis to diet. Since I do not have current literature from which to draw any conclusions (since you have presented none), I cannot state one way or another my position on the issue. You have to convince me. If you want to claim evidence that the appendix is a maladaptive trait based upon medical data, it will take more than a single outdated article and one I can't read to convince me. Until you do convince me, I remain unable to discard the null hypothesis on this issue.
Posted by: John Morales | August 25, 2009 10:46 PM
Rorschach, thanks for the confirmation.
anaxagoras,
Fair enough, though you've moved from a proximate to a secondary cause here, and such deaths would likely be attributed to sepsis, not to diarrhea.
Note that this is a similar circumstance to the above — the loss of protection caused by the absence of pre-existing flora which occupy that niche. It's the main reason why I choose not to use anti-biotic handwashes — the principle being leave well enough alone! :)
cf. Human Microbiome Project (HMP).
Posted by: Rorschach | August 25, 2009 10:46 PM
Well, for one it doesnt seem to make sense to me that evolution would put all its chips on the one area in the gut to be dependent on for gut flora restoration after a diarrhoeal illness.
And it's not the case that a diarrhoeal illness somehow "purges" the bowel from all bacteria anyway, you get inflammation of the bowel wall with cell shedding and inability to reabsorb water and nutrients and such, depends on the bug, but the picture of the bowel flora regenerating from one particular area after having been completely sterilized or something, is misleading IMO.
Anyway, interesting topic.
I still think the detrimental effects, based on our knowledge to date, outweigh the assumed benefits by far.
Posted by: anaxagoras | August 25, 2009 11:19 PM
Sorry, my comment (#125) should have been directed at both John M (#119) and Rorschach (#121). Didn't mean to leave you out.
Posted by: Ryan Egesdahl | August 25, 2009 11:21 PM
Rorschach #128:
As related to modern society, I agree with you. I don't think I want a doctor just cutting out a part of my body willy-nilly, though. Knives creep me out.
Posted by: truth machine, OM | August 25, 2009 11:27 PM
I have a problem with this biofilm-restoration of gut flora argument exactly because of that.
With severe diarrhoea, you die from dehydration, subsequent kidney failure etc, and loss of electrolytes, not from lack of restoration of gut flora if you happen to not have an appendix.
Fallacy of denial of the antecedent: Diarrhea kills. Restoration of gut flora doesn't prevent diarrhea. Therefore restoration of gut flora doesn't prevent death and isn't adaptive.
Death from diarrhea is a red herring that has no bearing on the gut flora argument. Gut flora serve many purposes, and an ability to readily restore them is adaptive.
Well, for one it doesnt seem to make sense to me that evolution would put all its chips on the one area in the gut to be dependent on for gut flora restoration after a diarrhoeal illness.
No one (other that you) said anything about putting all the chips on one area. The issue is simply what function(s), if any, the appendix has; there is no implication that it plays any exclusive role in survival of the organism.
Y'know, there's no point to having logic books on your shelf if you don't put what's in them into practice.
Posted by: Sven DIMilo | August 25, 2009 11:30 PM
the Machine!
Posted by: truth machine, OM | August 25, 2009 11:34 PM
I don't think I want a doctor just cutting out a part of my body willy-nilly, though. Knives creep me out.
My tonsils and adenoids were removed when I was a child; I miss them.
Posted by: anaxagoras | August 25, 2009 11:39 PM
On a different train of thought....
I've been thinking about MikeM's subjective impression of the link between appendicitis and Crohn's disease, and also Peter G's analogy of appendix as "our own on board petri dish". Maybe the biofilm idea might work in a different way from what the authors of the paper suggest. A major task of the immune system is differentiation of "self" from "nonself", and in the gut this is an especially tricky thing because the immune system needs to tolerate the helpful bacteria while still fighting harmful bacteria. To my knowledge (a few years old, granted), immunologists haven't figured out how the immune system makes the distinction in this case. Perhaps the biofilms in the appendix play a role in instructing the immune system which bacteria should be tolerated? Then, the inflammation of appendicitis may mis-direct the immune system to attack things that it shouldn't. I don't know much about Crohn's--would this be consistent?
Oh, and John Morales, I don't use anti-biotic soaps or cleaners either. Immunologically speaking, what doesn't kill you usually does make you stronger. :)
Posted by: truth machine, OM | August 25, 2009 11:40 PM
the Machine!
I shouldn't be here, as I have important things I need to get done. But then, that's why I'm here: it's a procrastination mechanism.
Posted by: John Morales | August 25, 2009 11:42 PM
tm, I think both Rorschach and I are arguing that the linkage between morbidity from diarrhea and the putative function of the appendix as a reservoir of bacteria as a justification for its evolutionary benefit seems spurious, no more.
Posted by: truth machine, OM | August 25, 2009 11:50 PM
tm, I think both Rorschach and I are arguing that the linkage between morbidity from diarrhea and the putative function of the appendix as a reservoir of bacteria as a justification for its evolutionary benefit seems spurious, no more.
To repeat myself, this is a red herring, because that isn't the justification that is given for its evolutionary benefit. And if you would read what Rorschach and I wrote carefully (not a habit of yours) Rorschach did "more" by suggesting that the failure of this linkage is an argument against restoration of the flora being an adaptive function of the appendix but, as I said, that's a fallacy of denial of antecedent. And he did even "more", by arguing that it is implausible that evolution would put such a function solely in the appendix -- a rather fundamental misunderstanding of selection and adaptation.
Posted by: truth machine, OM | August 26, 2009 12:00 AM
the linkage between morbidity from diarrhea and the putative function of the appendix as a reservoir of bacteria as a justification for its evolutionary benefit seems spurious
This alleged linkage goes back to Akika's ridiculous post:
The appendix as a back up reservoir for lost gut flora is ludicrous. Just as you said, then millions of people would not be dead from diarrhea
Of course, PZ said no such thing, because he knows that it isn't simply the loss of gut flora that causes death from diarrhea. In fact, he directly contradicted Akika:
reasonable != ludicrous
Posted by: Ryan Egesdahl | August 26, 2009 12:05 AM
truth machine, OM #133:
So were mine and so do I. Doing so almost killed me, too, in a sense; it was the time my mother discovered my penicillin allergy.
Posted by: Rorschach | August 26, 2009 12:13 AM
Might be.Not sure anyone knows that for a fact.
Glad we're back to the fallacies, however this one wasnt mine, I was pointing out that the argument that was being made for a evolutionary advantage of the appendix by ways of gut flora restoration doesnt convince me because it has no bearing on the course of any illness causing disturbance of said flora, be that infective diarrhoea or whatever.It would only have an effect after, and if, you survived the illness causing the disturbance first.
Care to explain why you think it is?
Posted by: amphiox | August 26, 2009 12:15 AM
Ryan Egesdahl, I only limited my discussion in post #116 as a direct response to this comment of yours in #113:
"Yes, but I am talking about right now, in the context of this paper. What it was in the past is not relevant."
You are not just "seeming" to go back and forth on this. You ARE going back and forth on this. It was the whole point of my previous posts that the past is relevant.
"we have to discount the effects of modern medicine and culture on the data because we are looking at the function of the appendix itself"
True, but that was not the point of my argument. I was talking about the relative benefit/detriment of the appendix right now, in the current environment in which it finds itself. Modern medicine and culture are part of that environment and cannot be discounted.
"We can say no such thing because we only understand its ailments, and not very well."
We have a very good understanding of the morbidity and mortality associated with appendicitis and its treatment. We may not know precisely what causes it or how it develops relative to gut microbiology or immunology, but we do not need to know these things to know the magnitude of the detriment associated with appendicitis. We know this magnitude very well.
"We understand essentially none of the benefits of the appendix"
This is not true. We have compared the health outcomes of people with and without appendices and have found no major significant differences. This sets an upper bound on the magnitude of any potential benefit of appendix function in the current environment. Any larger benefit would have been noticed in those studies.
We know the magnitude of one major detriment of the appendix very well, and we know the maximal possible benefit the appendix can provide, all within the context of the present environment. That is more than enough to estimate the likelihood of the appendix being detrimental or beneficial for humans in the present environment, and enough to extrapolate as to the balance of detriment/benefit of the appendix in the past, so long as we admit to assumptions derived on present observations extending into the past that may turn out not to hold, and thus compel us in the future to alter our extrapolation.
The issue of the appendix being currently a net detriment or net benefit is a question independent on the evolutionary history of the appendix, independent of its status as vestigial or not, independent of whatever function(s) it may turn out to have. These are all very interesting questions, and each informs us about the other, but we don't need to necessarily know all that much about one before we can say anything intelligible on the other.
On the question of relative benefit/detriment we in fact don't need to know anything at all about mechanisms or function or history. We need to know only one thing - magnitude of consequence. That boils down entirely to mortality, morbidity, and fertility rates compared between individuals who have appendices and individuals who do not, individuals who get appendicitis and individuals who do not. To answer this question we don't need to know why or how (which we need to know for the other questions), only what - and we have pretty good data already on the what, enough to make the preliminary judgment that the appendix is more likely than not detrimental in humans living in the first world, at the present time. Yes, the proper null hypothesis is neutrality for the trait in question. But we already have more than enough data test the null hypothesis and find it wanting.
This is my only point. I actually agree with you on most of the rest of what you've been posting.
Posted by: John Morales | August 26, 2009 12:17 AM
tm @131, it's probably my lack of acuity, rather than lack of care.
However, if I read what you wrote carefully, I get a confusing message:
So, restoration isn't adaptive, but an ability for restoration is? As I said, confusing.
Posted by: truth machine, OM | August 26, 2009 12:19 AM
I have a problem with this biofilm-restoration of gut flora argument exactly because of that.
Try to get it through your head that a bad argument for something is not a good argument against it -- that's a false dichotomy. Even if a thousand bogus justifications for a claim are soundly refuted, that does not pose any "problem" for the original claim.
[man, I really am wasting my time here]
Posted by: truth machine, OM | August 26, 2009 12:26 AM
it's probably my lack of acuity, rather than lack of care.
It's both. Ripping out of context part of my statement of the fallacy that Rorschach committed and treating it as a statement I am making is certainly not careful reading:
Do I really have to explain to you, as if you were a child, that if something is a fallacy, that means that the conclusion isn't valid?
Posted by: amphiox | August 26, 2009 12:30 AM
We've been going back and forth talking about the appendix from the perspective of the mammals, as an adaptive trait. We shouldn't forget to also consider the issue from the perspective of the gut flora, either.
The cecum is prime real estate for colonic flora, where they get first crack at the nutrient rich effluent coming out of the small bowel, before the reabsorption of water and nutrients occurs further down the large bowel, and before other colonic flora have a chance to exploit the same resources. It shouldn't be surprising to find biofilms being established there, as was described in the frog outgroup in the paper.
And if a diverticulum forms in the cecum for whatever reason, it wouldn't be surprising that the local gut flora would take advantage of it and establish a biofilm in it.
The resulting situation would be an appendix functioning as a reservoir for colonic flora, but the reason the appendix evolved and was preserved in some lineages and not in others may have nothing to do with this at all. The gut flora may just be exploiting this refuge for no other reason than because it happens to be there.
Posted by: John Morales | August 26, 2009 12:41 AM
tm @144,
No, that I understand. What I don't quite follow is how you apply it in this instance.
To recapitulate:
Denial of the antecedent: If p then q; not-p; therefore, not-q.
Rorschach: With severe diarrhoea, you die from dehydration, subsequent kidney failure etc, and loss of electrolytes, not from lack of restoration of gut flora if you happen to not have an appendix.
tm: Diarrhea kills. Restoration of gut flora doesn't prevent diarrhea. Therefore restoration of gut flora doesn't prevent death and isn't adaptive.
I don't consider that you've correctly paraphrased Rorschach. Can you please clarify?
Posted by: truth machine, OM | August 26, 2009 12:47 AM
Might be.Not sure anyone knows that for a fact.
No one knows for sure that gut flora serve many purposes? Don't be ridiculous. Since they do, the ability to restore them is obviously adaptive. Whether the appendix actually does that, to a degree that offsets its negatives, is what we don't know. (And let's not play this silly creationist game of demanding that we be "sure" of things, that we know them "for a fact"; all we need is to "know" them in the usual sense of empirical parsimony.)
however this one wasnt mine
I pointed out yours. As is your habit, you don't address my actual words.
I was pointing out that the argument that was being made for a evolutionary advantage of the appendix by ways of gut flora restoration doesnt convince me
But it's NOT the argument being made. ALL of the arguments being made here about morbid diarrhea are being made AGAINST the linkage. It's a STRAWMAN; the positive claim is not and never has been that restoration of gut flora prevents death from diarrhea. Since it's a strawman, beating it down does not pose a problem for the original claim -- an "entirely reasonable" one, as PZ said -- that "one function of the appendix that is significant in modern human populations is as a bacterial reservoir for recovery of gut flora after losses due to disease".
It would only have an effect after, and if, you survived the illness causing the disturbance first.
Yes, that's right. But it doesn't matter when it has its effect in order to for it to be adaptive, to provide a marginal increase in fitness.
Care to explain why you think it is?
I already did: that something provides an increase in fitness does not in anyway entail exclusivity of function.
I really must leave this all too familiar pit of sloppy thinking and go take care of business. Bye, guys.
Posted by: Ryan Egesdahl | August 26, 2009 12:53 AM
amphiox #141:
This is the concern I had, to which I alluded in that comment: that I wasn't successfully getting my point across. I'd blame it on the Asperger's, but I've had too many years of living with it for that to be an excuse.
How about we reset this conversation? I'm getting the feeling that we're not disagreeing about the same topics here. You're talking about the "current environment" and I am not; I am merely talking about the present independent of environment. What I want is evidence suggestive of adaptive and maladaptive pressures on human beings that have appendices in the present, independent of other traits like intelligence (meaning modern medicine and diet, etc.). Historical data would be needed to obtain that information, as would current medical statistics.
The only positions that I maintain here is that there is a null hypothesis that the human appendix is a neutral trait (since most traits are) and that sufficient evidence has not been presented to enable me to reject it. No amount of declaring "appendicitis!" over and over again will convince me, either, since that means you are rejecting potential benefits out-of-hand. Show me that, independent of modern medicine, possessing an appendix is harmful enough to reproductive capability to be a significant selective pressure, and that there are either no benefits or that the benefits are outweighed by the potential for harm. If you can show me these things, I will be able to reject the null hypothesis and accept your claims. You have not done so - you have only made claims that such evidence exists, which is contrary to my understanding of the facts.
Posted by: Rorschach | August 26, 2009 12:57 AM
@ 145,
Excellent point, and more likely than the evolutionary benefit theory.
I agree.And in terms of vestigial or not/evolutionary advantage, I wrote above that this advantage better be good, because peritonitis from a perfed appendix usually means death for poor ol' skippy.
tm,
care to explain how this syllogism you posted @ 131 as (rather distorted) representation of my argument, could possibly even formally be a FDA without the premise being in the form of a conditional?
Now you are misrepresenting what I wrote.I was obviously referring to your claim that we know that this is adaptive, I wasnt disputing the bit about the gut flora serving many purposes.Please, you can do better than that.
Posted by: truth machine, OM | August 26, 2009 12:58 AM
I don't consider that you've correctly paraphrased Rorschach.
That's because you're broken. I pointed out and addressed what he wrote, which you have simply ignored in your snipping: "I have a problem with this biofilm-restoration of gut flora argument exactly because of that." Go read what I wrote about that in #143. And what I wrote about a red herring. Death from diarrhea is irrelevant, since no one ever claimed that restoration of gut flora prevents it. Pointing out that it doesn't prevent it does not pose "a problem" for the "biofilm-restoration of gut flora argument", which rests on the general value of having intestinal flora. But it seems that the marginal nature of most adaptability and fitness is too subtle for you.
Posted by: truth machine, OM | August 26, 2009 1:02 AM
Now you are misrepresenting what I wrote.
No, you are, blatantly; you snipped off the part -- "Since they do, the ability to restore them is obviously adaptive." -- that addressed exactly what you say you were referring to.
Please, you can do better than that.
You apparently can't. Same old same old.
Posted by: John Morales | August 26, 2009 1:11 AM
tm @150,
Um, that was my opinion @119.
My issue was with my perception that you mischaracterised Rorschach's claim, but I hereby desist from arguing that further.
--
PS I too am a procrastinator... so I feel unapologetic in reminding you of your more pressing concerns! :)
PPS If I'm broken, then the average person is demolished.
Posted by: truth machine, OM | August 26, 2009 1:12 AM
care to explain how this syllogism you posted @ 131 as (rather distorted) representation of my argument, could possibly even formally be a FDA without the premise being in the form of a conditional?
Are you really so incompetent that you can't get from what I wrote to the standard form?
If restoration of gut flora prevents fatal diarrhea, it's adaptive. Restoration of gut flora doesn't prevent fatal diarrhea. Therefore restoration of gut flora isn't adaptive.
Of course the conclusion doesn't follow because preventing fatal diarrhea is not necessary in order for restoration of gut flora to be adaptive. Pointing out that restoration of gut flora doesn't prevent fatal diarrhea is arguing against a strawman.
Sheesh.
Posted by: Rorschach | August 26, 2009 1:14 AM
tm @ 131 :
Death from diarrhea is a red herring that has no bearing on the gut flora argument. Gut flora serve many purposes, and an ability to readily restore them is adaptive.
me @ 140:
Might be.Not sure anyone knows that for a fact.
No snippets left out.You just misinterpreted what I said. As if I would dispute that gut flora serves many purposes, sheesh.
Posted by: truth machine, OM | August 26, 2009 1:17 AM
Um, that was my opinion @119.
And yet Rorschach said that this irrelevancy is "exactly" why he has "a problem" with the position of Smith et. al.
My issue was
Sigh. This is so familiar. You said that you and Rorschach were saying "no more" -- but it's precisely Rorschach's "more" that I had addressed.
If I'm broken, then the average person is demolished.
No argument there.
Posted by: truth machine, OM | August 26, 2009 1:27 AM
As if I would dispute that gut flora serves many purposes, sheesh.
As I noted, you disputed either that or what logically follows from it. As I said, it's ridiculous to dispute that gut flora serves many purposes -- you agree; oh goody. Therefore it is adaptive. We KNOW this. I didn't "misinterpret" what you said, I accounted for all possible interpretations, each of which is absurd or pointless.
And that's where we are. Just what the hell is your point? Do you have some argument against this paper? Because pointing out that a lack of flora isn't how diarrhea kills isn't one.
Posted by: Rorschach | August 26, 2009 1:29 AM
tm @ 153,
I see your point, thanks for clarifying.Long way though from "diarrhoea kills" to "If restoration of gut flora prevents fatal diarrhea, it's adaptive."
The proposed theory is that biofilms in the appendix might help restore normal gut flora after a diarrhoeal illness and that this is good in evolutionary terms.
What I tried to point out was that a) the idea that the gut gets purged of all bacteria with every gastro bug is overly simplistic, and b) that I fail to see how this could be of any great benefit given that you have to survive the illness first to even get to the point where this could then help you recover.
I can see now how this second point could be seen as FDA,so thanks for pointing it out.
Posted by: Pikemann Urge | August 26, 2009 1:39 AM
Geez, we can't have a discussion without flaming. Yikes. I see amphiox is here but tmax isn't. Oh well, maybe TM,OM can add some useful comments to these points:
- Appendicitis begins in the colon, implying dietary causes
- Appendicitis can be cured non-surgically
- The appendix lubricates the ascending colon
- The appendix assists peristalsis
Now we're moving from biology to medicine but... any comments appreciated.
Posted by: Rorschach | August 26, 2009 1:49 AM
@ 158,
google is your friend.
Of course it can be "cured" non-surgically,with antibiotics.The natural course is 30% perforation.
The rest of those statements you threw out look pretty non-sensical.
Posted by: truth machine, OM | August 26, 2009 1:50 AM
the idea that the gut gets purged of all bacteria with every gastro bug is overly simplistic
Whose idea is that?
that I fail to see how this could be of any great benefit given that you have to survive the illness first to even get to the point where this could then help you recover.
Who said benefits have to be great?
I can see now how this second point could be seen as FDA,so thanks for pointing it out.
The FDA was, once again, in your taking a bad argument for something as an argument against it when you said in #121 -- which I quoted when I said it was an FDA -- that the "spurious" (indeed) argument about diarrhea is "exactly" why you have "a problem" with Smith et. al.'s argument. This is my general point about logic and has nothing to do with evolution or the details of this paper or the arguments for or against -- the existence of a spurious argument FOR a proposition can never serve as "a problem" -- an argument AGAINST the proposition.
Posted by: truth machine, OM | August 26, 2009 1:54 AM
Geez, we can't have a discussion without flaming.
There have been discussions without flaming, therefore it follows that we can have them.
Posted by: TheVirginian | August 26, 2009 2:00 AM
I just wish evolution had de-selected me for having an appendix, so that when I was fairly young, my parents would not have had to rush me to a hospital in the middle of the night for an emergency appendectomy.
Maybe God knew before I did that I would become an atheist and therefore was trying to kill me before I became damned to eternal torture, dunked in a sea of fire with a worm (or whatever it is, maybe my flaming, very painful appendix) gnawing at me from within, without any hope of surgical removal this time.
All I can say is, god or evolution (can't be both) work in very mysterious and sometimes painful ways!
Posted by: Rorschach | August 26, 2009 2:00 AM
Seems to me to be implied in the proposition that there is a need, via some sort of bacterial reservoir in the appendix, for from-the-grounds-up recolonization after a diarrhoeal illness.
And I dont think that's what happens.
Well, point taken.
Posted by: truth machine, OM | August 26, 2009 2:10 AM
Rorschach, let me present what I think is your argument, devoid of FDA elements:
Because you have to survive the flora-flushing illness first to even get to the point where restoration could then help you recover, and because the flora aren't completely flushed, it doesn't seem that the benefits of restoring flora are sufficient to outweigh the costs of potential appendicitis.
If that's fair, let me point out that this might be an argument for why many animals don't have appendices, but it's not an argument against the appendix functioning to restore the flora, since we do have appendices.
Posted by: Rorschach | August 26, 2009 2:17 AM
This was addressed, I think by Amphiox, upthread.
Mortality, morbidity and fertility rates between humans with or without appendix are the same.
Which would hint that the function of the appendix, whatever it is, is rather less obvious than being the sole restorator of the gut's flora.You would think that would be a really important survival trait.
Posted by: truth machine, OM | August 26, 2009 2:23 AM
Seems to me to be implied in the proposition that there is a need, via some sort of bacterial reservoir in the appendix, for from-the-grounds-up recolonization after a diarrhoeal illness.
And I dont think that's what happens.
Couldn't a bacterial reservoir in the appendix aid in recolonization after such an illness? Again, the benefit need not be great, nor the function exclusive.
But there is certainly a valid point here, which is that the more marginal the benefit, the weaker the argument is that the trait was selected for.
Posted by: Rorschach | August 26, 2009 2:24 AM
Sorry,mistake in 165. Should read health outcomes instead of fertility,since this is in regards to benefits of having an appendix.
Posted by: truth machine, OM | August 26, 2009 2:44 AM
This was addressed, I think by Amphiox, upthread.
I don't see any connection between what I wrote and and what he did; my point was a logical one, that net maladaptivity is an argument for why a trait such as an appendix is lost or doesn't occur, but it can't be an argument against a function that reduces the maladaptivity of an existing organ.
Mortality, morbidity and fertility rates between humans with or without appendix are the same.
I believe he said that the rates show that appendices are on net maladaptive in modern humans.
Which would hint that the function of the appendix, whatever it is, is rather less obvious than being the sole restorator of the gut's flora.You would think that would be a really important survival trait.
Uh, so you're arguing that the appendix must have some other function, one much more important than restoration of gut flora, yet less obvious? Well, as PZ said, it's possible that the caecum and appendix "are retained as entirely neutral characters that are not easily pared out without disrupting gut function" -- that would be enough to explain why we have an appendix even though it causes problems. If it also functions as a repository from which gut flora can be restored -- an "entirely reasonable" proposition he says -- so much the better.
Posted by: Rorschach | August 26, 2009 3:30 AM
No,Im saying that if having an appendix had important health benefits such as gut recolonization, we should be able to pick that up comparing health outcomes to people without an appendix.
And they seems to be no diffference.
Posted by: GuyGene | August 26, 2009 4:13 AM
Sounds like you are reaching for a solution again. It is very simple, the appendix has a purpose no matter how small its role may be. Case closed.
Posted by: Rorschach | August 26, 2009 6:14 AM
Sounds like you're a braindead dimwit who is regurgitating BS he was fed by his MacPastor or brainwashed parents.
Posted by: Ryan Egesdahl | August 26, 2009 6:38 AM
How rude the commentary around here has become! In any case...
GuyGene #170:
You're reaching if you say there is any purpose for an appendix at this point. First, there's no data to support such a conclusion. Second, "purpose" is not a very good term to use in biology. If you mean "function", then most likely you are right. Rarely does any part of the human body not serve some function, though not all functions are essential to life. If you truly mean "purpose" as in some transcendent revelation, well...I shouldn't have to tell you that such discourse has no place in scientific discussion.
Oh, and case most certainly not closed. In science, the case is never closed, or we would be missing the point of doing it.
Posted by: Rorschach | August 26, 2009 6:43 AM
No it hasnt.
GuyGene has shown himself to be a close-minded dimwit not only on this thread, and Im calling him one.
Thats not rude, thats fact.
Posted by: John Morales | August 26, 2009 6:48 AM
Ryan @172, indeed.
However, consider 'wisdom teeth' (third molars).
When I was a teenager, one of mine caused problems, and after an X-ray, I had all four extracted in one operation (under total anesthetic — chipmunk cheeks and significant pain for a week or so afterwards!).
They do serve a function (mastication), but I think they're pretty close to vestigial; they are problematic in many people.
'Intelligent design', my arse.
Posted by: Ryan Egesdahl | August 26, 2009 10:22 AM
Rorschach #173:
No need to become defensive because the comment wasn't directed at you specifically. I was talking about the namecalling I was seeing earlier. If that's just playful banter, then forget about it.
Besides, I called him out on his comment as well. My style is to make someone feel stupid. I just didn't know at the time I didn't need to try so hard.
Posted by: Ryan Egesdahl | August 26, 2009 10:29 AM
John Morales #174:
They don't serve a function in people that never have them emerge, as in my case. That was what I meant by "rare" when I said it. Most structures in the human body have existed for thousands if not millions of years, so it stands to reason that nearly every one of those structures would have some "function", even if it is only to be a cavity where a beneficial opportunistic infection is allowed to thrive.
Your arse is intelligently designed? I've seen some of those before. I like to look at pictures of them. No need to send pictures of yours, though - I have plenty for now.
Posted by: Stripe
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August 26, 2009 11:03 AM
Ryan Egesdahl - I don't find it strange that you demand evidence. Why would I think that?
Knockgoats - I though I solely referenced PZ's. No? I don't think I quote-mined or made any stuff up. But if you'd like to share where you think I've gone wrong...
Celtic_Evolution - I didn't forget to provide evidence. I was talking about assumptions. One needs no evidence to share an assumption.
amphiox - It's not a surprise, no matter what you're studying, that things tend to break down. Claiming that evolution accommodates the loss and degradation of function is not evidence for evolution.
Chiroptera - I would say the pattern of groups that have an appendix is easily explained by alteration in diet. Given that even in a single species the variation can be at either extreme I find no reason to have to rely on a common lineage to explain the patterns.
Dania Author - Who claimed any such thing as an explanation?
Tulse - Gee, your language is really bad. :|
Posted by: Sven DIMilo | August 26, 2009 11:11 AM
Third molars are not in any way vestigial; they are full-sized functioning molars for a lot of people. If aything is vestigial, it's the human jaw itself, which (for presumably adaptive reasons) which has shortened from the usual mammalisn (and even primate) snout just about as far as it possibly can shorten. This leaves often insufficient room for the wisdom teeth, but then they don't emerge until most of our ancestors had done most of their reproducing anyway.
Posted by: Tulse | August 26, 2009 11:22 AM
Quite right, my perspicacious interlocutor -- I am profoundly chastened by your observation.
Posted by: Dania
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August 26, 2009 1:01 PM
You're right. You didn't claim it explicitly. But you did say you were a creationist. As far as I know, creationists reject evolution as an explanation for life's diversity and believe that each species (or kind, or baramin... whatever) was independently created by
a magic man in the skyGod. Keeping this in mind, when you saidI understood you were proposing that mammals were created with a well developed appendix, and then
after the Fall, some animals changed their diets.
Now, maybe I was wrong in making these assumptions. If that was the case, I apologize. So, what exactly were you arguing for @43? If you feel like I misinterpreted your position, maybe you should clear things up?
Posted by: amphiox | August 26, 2009 1:25 PM
Stripe #176:
There is a pattern to loss and degradation in nature. The most interesting thing is it doesn't happen to everything. Only somethings are seen to degenerate with time, while other systems have been preserved intact, in some cases, for over 3 billion years.
The pattern is very specific and very obvious across multiple traits, and evolution explains this pattern very well.
Without evolution we are left with the inscrutable whim of capricious creator, who sees fit to preserve some things and let others degrade, with no rhyme or reason, other than to deliberate make it appear as if all life forms descended from a single common ancestor.
Believe this if you will, but don't lie and try to say that this is rational.
Posted by: Stripe
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August 27, 2009 2:03 AM
Tulse - Wow. I wasn't expecting you to take that seriously. :)
Dania Author - You're right. I didn't claim it explicitly. As a creationist I do reject evolution by random mutation and natural selection from a common ancestor as an explanation for life's diversity. I do believe that each kind was independently created by God. When I said all I did I was not presenting evidence. I was simply saying how far more reasonable (parsimonious, maybe) it is to assume that a feature degraded from a better one than to assume it developed from creatures entirely without.
Your assumptions may have been right, but they're not really relevant, are they?
amphiox - I'm not lying. In fact I've not made the claims that you are accusing me of. I think you need to stop jumping to conclusions and respond to what I've said rather than what you wish I'd said.
Evolution kinda has to explain things, doesn't it? But without evolution I'm sure we could come up with an alternative, right? I am certain that all the rationality and reasonableness that gave us evolution is just as capable of coming up with something else. :)
Posted by: Dania
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August 27, 2009 6:58 AM
Stripe,
And yet you accuse the authors' interpretation of the evidence to be "stupid" and unparsimonious. Look, you're the one who posits the existence of a supernatural being to explain that which is easily explained by the ToE. That is stupid and unparsimonius.
You're right. You were not presenting evidence. You were simply ignoring it.
Here, let me quote Brownian @70:
See your problem?
Posted by: Stripe
|
August 27, 2009 10:40 AM
No, I don't see the problem. I made none of the claims you are asserting I did and see no need to.
Posted by: amphiox | August 27, 2009 11:09 AM
Stripe, I didn't say you were lying, I said "don't lie". I'm asking you not to lie.
You are implying that your creationist position is "parsimonious". It is isn't.
You are implying that there is evidence supporting your position. There isn't.
These positions of yours are falsehoods. Perhaps you believed in them at the time you made them, in which case you are not lying. But I was not accusing you of lying then.
You may have valid spiritual, social and emotional reasons to continue believing as you do, and I have no problem with what you choose to believe, so long as you don't force it on me or others.
But now you have been here and been exposed to the evidence that these beliefs are not based on reason. Further arguments from you stating or implying that they are WILL be lying.
I am asking you not to do that.
Posted by: Dania
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August 27, 2009 11:43 AM
The problem is that you don't apply the principle of parsimony consistently or at all. If you did, you wouldn't be a creationist.
What claims am I asserting you did that you did not?
Posted by: Stripe
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August 27, 2009 12:44 PM
Dania - Your first response to me was, "The 'magic man in the sky did it' explanation is so much more parsimonious, isn't it?"
That is not my explanation.
I do accuse the authors' interpretation of the evidence as being "stupid" and less parsimonious than my own. But that accusation did not rely on anything in your response.
I was not ignoring evidence, I was quoting an explanation and sharing what I regard as a better one. You do realise that explanations are not evidence, right?
I see now that you've suggested some evidence as being against me. Would you like to discuss the evidence for and against the competing explanations?
But if you're just going to insist that creationists can never contribute anything of value It's not going to be worth my time, is it?
amphiox - I'm not implying anything. I stand firmly upon the idea that it is more reasonable to assume that a feature degraded from a fuller example than to assume that a feature arose where there was no feature before. This holds true for any field of science you want to name. You need not bring up that I happen to be a creationist and try to insist that this somehow disqualifies me or makes me a liar.
If you consider my comments in this thread to be "forcing" things on others then perhaps you need to grow a thicker skin, no?
I'm open to examining evidence, but for you to insist that I must either abandon what I believe or be a liar is a profoundly unhelpful statement to make. Who knows? It might be you that is the one who is wrong.
That's possible, right? You might be wrong, right?
Posted by: Nerd of Redhead, OM
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August 27, 2009 12:51 PM
Stripe, show us your idea is scientific by citing the peer reviewed scientific literature to back up your assertions, starting with concept that creationism is a scientific idea. Until you can do that, your unscientific arguments will always fail in a scientific debate.
Posted by: Dania
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August 27, 2009 2:21 PM
Let's get something out of the way first. I do not necessarily agree with the authors' explanation. I'm not entirely convinced that the appendix independently evolved 2-4 times, as the authors claim. My position is that more data is needed. So, don't expect me to defend their interpretation against your proposed explanation, because I think it's possible (maybe even likely) that the common ancestor of all mammals had an appendix.
But that's not what you mean, is it? Your "explanation" is not that the last common ancestor of all mammals had an appendix. Of course not, because you're a creationist. What you would propose as an explanation is that mammals were created (when? how? by whom?) with an appendix. That isn't parsimonious. It's problematic because it raises more questions than it answers, and because it requires the existence of a never observed entity.
Who said creationists could never contribute anything of value? If you think you have something to contribute to our current scientific understanding, please do it. But, as you surely know, the place to do that is... the peer reviewed scientific literature. You don't do science on a blog. You can talk about it, sure (that's what this thread has been all about). But the peer reviewed scientific literature is where science is done.
This doesn't mean I don't want to engage you. In fact, I will happily do it. Maybe you have some evidence I was not aware of? Maybe you can show me that, after all, creationism has some merit? Who knows, maybe I'm wrong and you're right. I'll simply follow the evidence wherever it leads me. So, all you have to do is show me that the evidence leads to creationism and I'll change my mind. Evidence is all I'm asking for.
Posted by: truth machine, OM | August 28, 2009 5:27 AM
But if you're just going to insist that creationists can never contribute anything of value It's not going to be worth my time, is it?
While it's possible that some creationist somewhere can contribute something of value, you yourself never do because you're grossly ignorant and your thought processes are crap, so indeed your posting here is not worth your time, so you might as well stop.
Posted by: truth machine, OM | August 28, 2009 5:31 AM
I stand firmly upon the idea that it is more reasonable to assume that a feature degraded from a fuller example than to assume that a feature arose where there was no feature before.
It's not an assumption, you git, it's an inference from the evidence. What you are standing firmly upon is the idea that ideology trumps fact.
Posted by: truth machine, OM | August 28, 2009 5:36 AM
No, I don't see the problem. I made none of the claims you are asserting I did and see no need to.
Danina, only an imbecile would offer this sort of response to your post; you will never reach him.
Posted by: truth machine, OM | August 28, 2009 5:42 AM
Evolution kinda has to explain things, doesn't it? But without evolution I'm sure we could come up with an alternative, right? I am certain that all the rationality and reasonableness that gave us evolution is just as capable of coming up with something else. :)
Just as, without elliptical orbits for the planets, all the rationality and reasonableness that gave us elliptical orbits is just as capable of coming up with something else.
My hypothesis to explain someone like Stripe is fetal alcohol syndrome.
Posted by: truth machine, OM | August 28, 2009 6:07 AM
No,Im saying that if having an appendix had important health benefits such as gut recolonization, we should be able to pick that up comparing health outcomes to people without an appendix.
Well, perhaps you're just a terrible communicator. In any case, I've already explained why this is wrong: "net maladaptivity is an argument for why a trait such as an appendix is lost or doesn't occur, but it can't be an argument against a function that reduces the maladaptivity of an existing organ". See, we know that a tendency toward appendicitis is a deleterious feature of the appendix so, if there's no statistical downside to having an appendix, we would expect some countering beneficial feature. And if there is a statistical downside, it might well be even worse if such a beneficial feature were absent. Any way about it, since the statistics reflect net adaptivity, there's no inferential path from the statistics to presence or absence of some specific trait that only contributes to the net; your "should be able to" is simply false.
Logic: you're stunningly bad at it.
Posted by: John Morales | August 28, 2009 6:25 AM
tm @193,
Perhaps. If Rorschach* had written "No,Im saying that if having an appendix had important net health benefits (via such as gut recolonization), we should be able to pick that up comparing health outcomes to people without an appendix.", would you have such a problem with what he wrote?
Or perhaps, he's not a great communicator?
(Leaving aside relative competence vs. absolute competence)
--
* I do wish you'd indicate who you are quoting; many times I have to paste and search to find the relevant comment from which you quote.
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Posted by: Grant Dexter | August 28, 2009 12:49 PM
Stripe here...
Nerd of Redhead - No idea is shown scientific by being cited in any forum. No exception for peer reviewed scientific literature. And you've made the same mistake as all the others who have responded to me. The fact that I am a creationist is of no relevance to any evidence I might provide.
Dania - What I mean is exactly what I said. PZ Myers believes the most parsimonious explanation is that modern animals descended from a common ancestor that lacked an appendix. I find it far more reasonable to assume that creatures descended from creatures that had better appendixes. My "explanation" has started and finished there.
You implied that creationists could never contribute anything of value when you said, "The problem is that you don't apply the principle of parsimony consistently or at all. If you did, you wouldn't be a creationist".
I do not agree at all that peer reviewed scientific literature is the only place science can be or is done. Why would you say something like that? Especially when you claim that, "Evidence is all [you're] asking for"?
Evidence for the fact that common descent plays an insignificant role in appendix development is included in the original post, Appendixes "are variable in size ... within a species ... some humans are born without an appendix, and within the majority that have them, there's at least a two-fold variation in size."
Large variation within a single species shows that something other than common descent has the greater impact on the makeup of the appendix.
Posted by: Nerd of Redhead, OM
|
August 28, 2009 1:05 PM
Stripe/Grant idiotically bleats:
Sorry, if you were following the rules of science, you would believe in evolution due to the overwhelming evidence. That fact that you don't indicates your methods and thinking are not scientific, and everything you say must be put through a fine filter to determine the truth from the fiction. Like creationism is scientific, which is a total fiction. As is also indicated by:Sorry, that is the only place that science is done. Which is why creationism is wrong, and your opinion on this is irrelevant.Posted by: Dania
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August 28, 2009 1:47 PM
Obviously. No serious biologist would claim that the last common ancestor of all animals had an appendix. We still don't know how it looked like, but it must have been simpler than, say, a sea sponge. Are you sure you meant animals?
Really? Your "explanation" starts and finishes there? So, you don't think you need to explain where the first "creatures that had better appendixes" came from? Is it turtles all the way down?
No. I implied that creationism is not parsimonious. It isn't. I've already told you why.
Yes, evidence is all I'm asking for. I and all the other scientists. But even if you managed to convince me, your ideas would still have to pass the peer reviewed process to be taken seriously by the scientific community. That's how science works, whether you like it or not.
What is that even supposed to mean? All it shows is that the appendix is not being actively selected for, thus allowing for large variation within that species. It really is just that. I don't see how that helps your case.
Posted by: Grant Dexter | August 28, 2009 2:44 PM
Nerd of Redhead - I can follow the rules of science which justifies my skepticism of evolution and holds me accountable to the evidence. That you dismiss any ideas I might share based on my skepticism of a theory only shows that it is you that is acting against the "rules of science".
For a scientist everything everyone says must be put through a fine filter to determine the truth from the fiction. That you single out groups and label them suspect is no reflection on my nature.
Nerd of Redhead - If you insist science can only be done within a peer reviewed environment then you've just eliminated the validity of a large number of the scientific revolutions that characterise our history. I believe you should give up this notion that people must think alike or subscribe to some system in order to be doing science.
Dania - A serious biologist might claim that the last common ancestor of all animals had an appendix if he were to examine the evidence and adopt a hypothesis other than evolution. I am sure I meant animals.
I don't think I need to explain where the pre-existing creatures came from unless we are going to start discussing something else. I deliberately limited the scope of my statement so that we might be able to discuss the evidence that has been presented already. I'm not willing to devote a lot of effort into a broad defence of YEC on this thread.
Large variation within a single species shows that something other than common descent has the greater impact on the makeup of the appendix. Humans can be born with no appendix or they can be born with different categories. These differences are not due to a different evolutionary path for each. They are due to other considerations.
Posted by: Stripe
|
August 28, 2009 2:48 PM
Ahah. Typekey remembers me again. :)
Posted by: Dania
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August 28, 2009 4:39 PM
Ah, a variation of the old "Newton was not peer reviewed!" defense. Typical. Also, irrelevant. The methods of publishing scientific work have changed since then. Peer review is how science is done now. The fact that things were different when those "scientific revolutions that characterise our history" were made doesn't change that fact.
What other scientific hypothesis is there to adopt? Note the emphasis on scientific. Can you formulate it in scientific terms? Remember, it has to explain all the evidence that the ToE explains and it can't be contradicted by any evidence. And don't forget to explain how said hypothesis could be falsified... that's important too.
Oh, and the theory of evolution is not an hypothesis. It's a theory. I'm not nitpicking, this distinction is crucial in science.
OK, but it's a pertinent question. Your explanation raises even more questions than it answers. That's not a good thing.
And how does the evidence presented support your statement? You have not explained that. And you also ignored Brownian's point.
"Something other..." Are you being this vague on purpose? Do I really need to ask what you think this "something other" is?
Indeed. And I've already said what those "other considerations" are. It has to do with the low or absent selective pressure to keep the appendix in humans. The ToE accounts for that, while you haven't even attempted to provide a coherent explanation.
Posted by: Stripe
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August 30, 2009 7:31 AM
Dania - Newton was not peer reviewed is not a defense! It's a fact.If you think science must be done according to what a majority considers "proper" then you're flat out wrong. Most scientists do adhere to the peer review system these days and most who don't never get very far. But saying that this is how it is done has no weight against actual evidence. Something passing a peer review is not evidence for it.
There are thousands of scientific hypothesis one could adopt. They're called ideas. :)
Asking further questions about an idea might be a good idea if you've first understood the idea. Something that raises more questions is not necessarily a bad thing. It might simply be a sign of a very confused audience.
I've explained how does the evidence presented supports my statement. Brownian's insistence that older animals have lesser appendixes is fairly comical. I wonder which fossilised appendixes he's been studying. :)
Yeah, I've been vague with what I think this "something other" is. I think that creatures have an innate ability to respond to their environment. Thus two similar populations in two different environments will quickly develop unique characteristics because of their differing responses to the environment rather than because of random mutations and natural selection.
Posted by: Nerd of Redhead, OM
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August 30, 2009 7:50 AM
Stripe, scientific revolutions come from within science, not from the outside. Quite lying like that to try to justify your ignorance, stupidity, and just plain bullshitting. You have nothing to offer to a scientific debate, any more than the anti-AGW people, and your failure to cite the literature is all we need to see. You have no real idea how science is done, and I speak as a 30+ year practitioner of science. Science isn't about ideas, but evidence. Which you have no idea of how to interpret.
Posted by: John Morales | August 30, 2009 8:10 AM
Stripe:
Well, that's vague, alright! ;)
BTW, Stripe, if both populations adapt to their current environment over time, aren't they responding similarly (i.e. adapting), rather than differently?
Heh.
Posted by: 'Tis Himself, Quel Dommage
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August 30, 2009 8:17 AM
Most of these "ideas" are in a subgroup called "dumb ideas" or a related subgroup called "stupid ideas."
Science isn't about having an idea and seeing if it's true or not. Science is about looking at the evidence and coming up with an explanation. Testing this explanation is done by finding other evidence and seeing if the explanation applies to this new evidence. That's how science works.
Posted by: Knockgoats | August 30, 2009 8:23 AM
Grant Dexter
A serious biologist might claim that the last common ancestor of all animals had an appendix if he were to examine the evidence and adopt a hypothesis other than evolution. I am sure I meant animals.
You are a complete ignoramus. You quite obviously haven't the slightest idea what the scientiifc meaning of "animal" is.
I'm not willing to devote a lot of effort into a broad defence of YEC on this thread.
Because you know very well your idiot bletherings would be torn to shreds.
Posted by: 'Tis Himself, Quel Dommage
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August 30, 2009 8:29 AM
Reading this, I really doubt you have any idea about how natural selection works.
Posted by: Dania
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August 30, 2009 2:15 PM
It's an irrelevant fact that creationists like to use to defend themselves when we ask them why they're not disputing evolution under the peer review process. If you have evidence that will falsify evolution, why aren't you working on your article for Nature or Science? If you think you have evidence for creationism/ID, why don't you put it out there? Why don't you bring it to the attention of the scientific community? What's your problem?
But that is how it's done. You have to convince the experts in the relevant field that your ideas have merit, and to do so you have to present rigorous, evidence-based arguments in its defense. That's what peer review is.
It's an indication that your work was at least considered worth being looked at. Of course that passing the peer review process is just the beginning. Your work will be continually subjected to scrutiny after being published.
You have no idea what a scientific hypothesis is, do you?
I haven't understood the idea because you haven't stated it clearly. Really, I think you're a bit confused. Read the title of the paper again: Comparative anatomy and phylogenetic distribution of the mammalian cecal appendix. Why the hell did you start talking about animals?
Badly, if at all.
FFS, Stripe, Brownian clearly meant older organisms evolutionarily speaking. Like when we say that sharks are older than humans. Now, I know you don't accept that. But then you can't really spin the results shown in this paper in your favor, because it is entirely based on evolutionary theory.
Look at this phylogenetic tree. Do you accept that all those species share a common ancestor? If you don't, forget this paper. Nothing in it makes sense if you deny common descent.
*sigh*
Still vague. What makes you think that? What is this mysterious 'innate ability'? How do the creatures 'respond to their environment'? By what mechanisms?
I'm not sure what you mean by that. Are you saying that speciation occurs not because of natural selection and genetic drift, but because of 'an innate ability to respond to their environment'? Evidence?
Posted by: Stripe
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August 30, 2009 11:42 PM
John Morales - If both populations adapt to their current environment over time they might well be described as responding similarly (i.e. adapting), rather than differently. But I didn't say that because I meant something else. :)
'Tis Himself - Sure, many ideas are dumb. But I see no real difference between your two descriptions. How is, "Having an idea and seeing if it's true or not" substantially different from, "looking at the evidence and coming up with an explanation"? If you had an idea and wanted to test it would you not use evidence?
Dania - I am "putting my idea out there". What are you talking about?
I do not accept that all species share a common ancestor. I know this paper assumes evolution as a fact. I know nothing in it makes sense because of that. Professor Myers made that pretty clear in the beginning. I was attempting to share something that stayed away from the areas he said I should not mess with.
Yes I am saying that animals adapt because of 'an innate ability to respond to their environment'. The evidence I have already shared.
Posted by: Nerd of Redhead, OM
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August 30, 2009 11:52 PM
We don't give a shit what a creationist thinks about scientific ideas. What part of that statement don't you understand? Especially when they are wrong, but can't admit it. The genetic evidence is just too compelling. You are to ignorant to have any good ideas, and too stubborn to learn anything. Your posts are just a waste of your time.Posted by: Dania
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August 31, 2009 5:35 AM
I'm talking about engaging in the evidence for evolution via academia. As Nerd pointed out, scientific revolutions come from within science. If you want to disprove evolution (and that would be quite a revolution), you have to do it by doing science.
Thanks for not answering my questions above.
Except that the evidence doesn't support your idea, and is not problematic for evolution. YEC doesn't explain the evidence you shared better that the ToE.
Posted by: Dania
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August 31, 2009 7:18 AM
I said "evidence", not "idea". I know you have a lot of (stupid and uninformed) ideas. The problem is that you have no evidence to back them up.
Posted by: Stripe
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August 31, 2009 11:00 AM
Dania - I have used the words evidence and idea both. You're going to have to rightly divide between the two.
Thanks for the discussion. :)
Posted by: Dania
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August 31, 2009 2:42 PM
But you haven't presented evidence to back up your idea. And you haven't stated your idea clearly. Oh, and you also ignored my questions. And didn't bother to address most of the points I made. In other words, you've been evasive since the beginning of this discussion.
I don't think you've ever been interested in an honest debate. But then, that's exactly what I've learned to expect from creationists...
Posted by: Nerd of Redhead, OM
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August 31, 2009 2:52 PM
Using the words improperly mean nothing. If you have no idea on how scientific ideas are formulated, and what they should do, or what scientific evidence entails, you have nothing but empty vacuum for what you say. Which is what we have been saying all along. Evolution is a scientific theory, and is only changed by more science.Posted by: bercugebestho | September 19, 2009 12:52 AM
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