The appendix does not help humans digest cellulose. That is why it is considered to be vestigial.
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@pevaquark & @T_aquaticus & @jpm :
I don’t believe anyone gets anywhere disputing Vestigial anything. Too much room for problems with terminology and so forth.
Letting vestigial topics dominate the discussion is like letting the Koch Brothers dominate a conversation on Global Warming by discussing how clean their coal is.
The topics (whether it be clean coal, or vestigial organs, or % Chimp DNA - - though endless interesting - - are not low-hanging fruit in regards to the main issue of defending and educating Evolutionary principles.
In a paper referenced by the paper @Ashwin_s linked above it does indicate that the appendix has appeared 38 times and been lost 6 times. An interesting paper by the way.
The Cecal Appendix: One More Immune Component With a Function Disturbed By Post‐Industrial Culture
https://onlinelibrary.wiley.com/doi/full/10.1002/ar.21357
And from the Conclusion
So even if Darwin got it wrong in general (he was only aware of the appendix in humans) it still supports evolution as the appendix appears as needed.
Yes @Ashwin_s I know you will argue that this just means evolution is not falsifiable. I prefer to think that the theory of evolution is robust enough to account for new data.
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Why do you think it disappeared? Not a whole lot of fossil appendixes (?) around. Are you saying it independently evolved 32 times? References?
You aren’t taking into account the history of the theory. I agree there isn’t much that could disprove the theory, TODAY. That’s a sign of strength. 150 years ago? There was tons! But an overwhelming amount of evidence gathered since then have come to the same conclusion. Common ancestry. The odds are of so many disciplines coming to the same conclusion just by coincidence is extremely low. we aren’t going to throw out a crazy successful theory because of a few anomalies. No theory in the history of science has EVER agreed with every empirical observation. The fact that evolutionary theory can accomodate new and unexpected data so well is because it’s been so successful in explaining a wide range of data. Also, I’m not sure the human appendix is vestigial either due to the number of times its evolved independently but it’s something I haven’t put much time into thinking about. Finally, vestigial is defined independently of evolutionary theory. A vestigial trait is a reduced and rudimentary structure compared to the same structure in other organisms. If functional, they perform relatively simple, minor, or inessential functions using structures that were clearly designed for another purpose
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The paper I cited claims that…
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. The appendix has evolved minimally 32 times, but was lost fewer than seven times, indicating that it either has a positive fitness value or is closely associated with another character that does. These results, together with immunological and medical evidence, refute some of Darwin’s hypotheses and suggest that the appendix is adaptive but has not evolved as a response to any particular dietary or social factor evaluated here.
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https://www.sciencedirect.com/science/article/pii/S1631068312001960
Right now, I am just glad someone is willing to admit the appendix is non vestigial. 
Frankly, I find it hard to believe the appendix evolved 38 or 32 times (maybe @jpm does too). … It just means that the appendix is found in places where it should not be (according to CA) around 30+ times… and is assumed to have emerged on its own.
If you want to see that as a strength, it’s your choice.
Sigh…
Neither does the brain (digest cellulose)… is it vestigial.
We can’t insist an organ have the function we want it to have… there is no evidence the appendix had anything to download digesting cellulose… if the paper I cited is true… it’s the contrary. It had nothing to do with it.
You’ve made this false equivalency here and seem to be making up arbitrary definitions of what vestigiality means apart from any scientific definitions.
Same argument from a few days ago that again seems to be based off of a fundamental misunderstanding of what the word even means:
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The appendix, as part of the caecum, does help digest cellulose in other species.
No. If you read the Laurin paper it appears to have evolved twice and it only appears in those descendants. I think of it as evolution finding a tool which it then uses only when necessary. It appears when conditions render the presence of the appendix an advantage and disappears when it is no longer an advantage.
How do you know that digesting cellulose is the main function of the appendix? Or the first function that evolved, for that matter?
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Previously it was thought that the sack-like rabbit appendix served primarily as a reservoir for the bacteria involved in hindgut fermentation. That explanation, however, did not account for the absence of an appendix in other animals with similar digestive systems or for its presence in humans.
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Does the appendix serve a purpose in any animal? | Scientific American
@pevaquark:
Both my comparisons to cancer as well as the brain were to drive home that some assumptions are wrong.
1)An organ susceptible to sickness is useless.
- Cellulose digestion is the major function of the appendix.
It can happen two ways as far as I see.
- convergent evolution.
- on and off switches in the genome. (In which case nothing is truly vestigial).
Option 2 sounds a little Lamarckian. I thought the paper was referring to option 1. Can you share which part of the paper you are referring to?
It is kind of hard to miss. From the section
And a little further down.
So the paper still supports Common Descent even if the appendix is not vestigial. There are further references to papers supporting the idea of ‘constitutional responsiveness’ but I haven’t had time to chase them down.
Hi Bill,
I know the paper supports common descent even though the appendix is vestigial. Never claimed otherwise.This entire chain of discussion happened because i mentioned in passing that the appendix was not vestigial and people here disagreed with me strongly.There were even references to being influenced by “anti-evolutionary” creationists…
‘‘constitutional responsiveness’’ is an interesting term: it refers to the “ïnherited ability to respond to environmental variation.”
Recurrent phenotypes is the phenomenon of the phenotypes being found (in this case the appendix) across the evolutionary tree. I found a good paper to explain the phenomenon. i will quote some interesting information and the source.
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Recurrent evolution has most commonly been studied at the level of organismal phenotype (fig. 2), comprising an extremely rich field with hundreds of articles spanning three centuries exploring a wide diversity of recurrent phenotypes and lineages (Scotland 2011). A central concern of phenotypic work has been understanding the physical or genetic causes for recurrence. This pursuit often focuses on distinguishing between convergent evolution and parallel evolution (a distinction which itself has been extensively debated; Arendt and Reznick 2008; Scotland 2011). Generally, the distinctions follow etymology: parallel comes from the Greek for “beside” + “each other” (Παρα + αλληλος) and thus involves lineages with initially similar starting points arriving at similar endpoints by taking similar paths; on the other hand, convergence comes from the Latin for “with or together” (com-) and “to incline, tend toward” (vergere) and thus generally involves lineages with different starting points taking different paths to arrive at similar endpoints. For instance, one proposed distinction between parallelism and convergence focuses on the starting points for the two lineages: whether similar (closely related species, parallel) or different (distantly related species, convergent). Another proposed distinction focuses on paths (the specific genetic mutations underlying the changes) taken by the two lineages—whether the same (parallel) or different (convergent) (Arendt and Reznick 2008). Importantly, the two proposed distinctions are related since, because of their higher genetic and developmental similarities, closely related species are more likely to evolve similar traits by identical genetic changes than are species with more disparate biology (although this is not always the case; Arendt and Reznick 2008).
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This drawing will give you an idea what they are talking about.
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Recurrent evolution of the same genomic characteristics suggests predictability of evolution, elucidating the rules of genome evolution by revealing commonalities of evolutionary forces experienced across disparate lineages (Conway Morris 2009). We believe that the wealth of recurrent genomic features indicate unappreciated similarity of fundamental forces across lineages. Although the large number of genomic characters and finite nature of sequence space implies that genomic recurrence may sometimes occur simply by chance (see below), many cases have now been unearthed that suggest specific forces driving genome evolution down similar paths in different lineages. Identifying and understanding these forces or causes are perhaps the major challenge of the study of recurrent genome evolution.
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Source:Widespread Recurrent Evolution of Genomic Features - PMC
There is a difference from suggesting change driven by random events as opposed to change directed by “Laws of nature”. I find this paper and line of investigation very very interesting.
Really? This is what one of the authors would think of what you said:
“The creationists have misinterpreted, either mistakenly or deliberately, our work,” Laurin says. “I was horrified when I found out what they wrote about my paper. And since I’m the author, I can tell you it’s a very severe misinterpretation when they stated that our results indicated that the appendix had no evolutionary pattern.”
What do you think of Laurin’s statement?
All in all, what is your main point at this point? What is your hypothesis? What justifies your analysis of a single statement in a paper to be more valid than multiple authors with doctorates in relevant fields that spent years analyzing data?
You have singled in on one statement from their paper while ignoring most of it. How about we check out Laurin’s 2017 paper too on the appendix:
Morphological evolution of the mammalian cecum and cecal appendix
There are several highlights I suppose but:
The great differences in evolutionary rates, and especially the high evolutionary rate of the cecal appendix in Euarchontoglires, support our earlier suggestion (Laurin et al.,2011; Smith et al.,2013) that this character is a recurrent phenotype. It is particularly recurrent within Euarchontoglires, with numerous transitions in rodents and primates, and it is essentially ubiquitous in lagomorphs. Interestingly, the heterogeneous pattern of this recurrence appears to be explained better by the phylogeny than by the ecological factors tested.
The appendix does appear is nested hierarchies determines via other means with a few interesting appearances. If you reject nested hierarchies, then you don’t have any argument to begin with I think.
As for the appendix being vestigial, that’s hard to say. For the 12 species who lost the appendix it certainly was for them for a time before it was gone altogether. And while it serves some purpose for humans, it’s hard to imagine it faces any selection pressure for us anymore (though it clearly once did as the paper establishes very well- the appendix is NOT vestigial for mammals as a whole and has some use for us, but for many mammals they lost it entirely as it was vestigial and then disappeared).
Also, that’s my fault entirely. I apologize for my presumption. The appendix and vestigial structures/genes in general as misunderstood and misused by many anti-evolutionary creationists (I notice you put it in quotes most likely because you reject the possibility of being an evolutionary creationist). I wrong assumed you were just parroting their common arguments.
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Recurrent phenotype means that the phenotype/trait evolved independently again and again… i.e, they did not share the trait with a common ancestor.
The evolutionary mechanisms by which this is supposed to have happened is convergent evolution and parallel evolution.
This kind of conclusion can be arrived at only if the re-emergence of the trait cannot be explained in terms of inheritance from a common ancestor.
To paraphrase …
The authors are claiming the same… and they believe it happened by evolutionary means.
The paper does point to an “evolutionary pattern”- That of recurrence…
I dont know about creationists, but i certainly would question the “random” nature if this recurrence.
I see. So what does this figure mean?
The top part of the figure was the 2013 paper showing 5 appearances of the appendix and then inherited. The updated paper was corrected- there was only one appendix appearance in this clade and it was inherited by all the common descendants (though a few lost it).
Wrong for the appendix. The other appearances are interesting though and the reasons for them are discussed in the paper- the morphology of the appendix plays a role, but all in all there may be a deep evolutionary link (like the hox genes for fish fins and human fingers).
Can you clarify? The paper discusses what natural features led to its appearance and which things didn’t.
Are you saying the paper was incorrect?
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Corroborating this view that the appendix has an adaptive function is the finding in this study that the appendix has evolved a minimum of 32 times in mammals.
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Have they retracted the above claim and reduced the overall no: to 1?
The figure you cited shows the appendix as having appeared 5 times. Its easy to count. Have the authors updated this finding with a different figure? The drawings in the paper i have access to look like this:
The top part shows the cecum… and the bottom half records the presence/absence of the appendix.In the drawing,Strepsirhini developed the appendix 5 times while the cecum was present throughout the clade indicating one common ancestor for the cecum.
Yes.There may be a deep evolutionary link… such a Pre-programmed code in the DNA which allows the appendix to developed as and when it is needed. We will be able to evaluate how “evolutionary” that possibility is when we get more concrete info about it.
I was saying the same thing you said. I don’t think the process of the appearance of the appendix is random. There must be some mechanism which controls the appearance and disappearance of the appendix.
Current Darwinian evolution is stochastic.However, if the appendix appears and disappears based on environmental stimuli, the mechanism is unlikely to be stochastic. There will be a clear cause and effect sequence… There must be some kind of stimuli which cause particular genes to switch on/off etc. And it will be very exciting to understand these things.
I dont reject nested heirarchies as an observation of nature. My only point is that a nested heirarchy will form only if there is a specific/well defined element of regulation applied on random changes.I dont see natural selection providing the kind of regulation (because its a tautology that is not well defined).
Look, if you accept the Laurin paper, its time to put this story to rest. There is no statistical evidence that the importance of the appendix changes based on change in diet. The environmental factors that make it necessary to have an appendix are not clear.
lets just conclude and say that there is no evidence to the claim that the appendix is vestigial in human beings.
Apology accepted. I don’t keep these things in mind. People just keep asking why i am harping on this while it really doesn’t disprove evolution… and i have to explain.
Frankly, i would love to bring this discussion on the vestigiality of the appendix to a close.
All of us seem to agree on the facts right now… we are just nitpicking on semantics (I think semantics is important. But i don’t think discussing it will be all that fruitful).
Though i did learn from the discussion. and found some interesting papers.(I am especially keen on reading up on recurrent phenotypes)
So thanks to all for that.
@gbrooks9, @T_aquaticus, @jpm , @Bill_II, @AMWolfe
i think that different diet may cause less cases of appendicitis:
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