Purpose of Appendix Believed Found

CambodiaSam sent in this story, which opens: "Some scientists think they have figured out the real job of the troublesome and seemingly useless appendix: It produces and protects good germs for your gut. That's the theory from surgeons and immunologists at Duke University Medical School, published online in a scientific journal this week. For generations the appendix has been dismissed as superfluous. Doctors figured it had no function. Surgeons removed them routinely. People live fine without them. The function of the appendix seems related to the massive amount of bacteria populating the human digestive system, according to the study in the Journal of Theoretical Biology. There are more bacteria than human cells in the typical body. Most are good and help digest food. But sometimes the flora of bacteria in the intestines die or are purged. Diseases such as cholera or amoebic dysentery would clear the gut of useful bacteria. The appendix's job is to reboot the digestive system in that case."

Comments

Polio, Asthma & Allergies

[eldavojohn]

I have studied little biology or medical subjects though I've read studies about this same sort of thing happening with asthma, polio & allergies. I think I've posted about this before but anecdotally I noticed there were no farmers who had allergies or asthma as I grew up and worked on farms with them. The young kids would play in hay and run around in the mud outside when it rained. So it seems that a problem with being an overly hygienic society today (as the article notes) is that we don't expose our young to these pathogens early on so they never adapt to them and suffer exposure to them later. This is why I recommend against anyone installing an air purifier in their home. It's a great idea--if you never plan on leaving your home.

I can't find the research but I thought a long time ago that a German study was done to find out why polio was "a middle class disease." If I recall they found that poor children were exposed to it since birth and rarely suffered from it since they were exposed to it always. The middle class children would be protected as infants but once exposed to it, their bodies would not be able to fight it. The upper class would take all costs to reduce exposure to it at all times--and they could.

Now this research is interestingly related in that appendicitis may be something that occurs due to our lack of exposure to diseases that destroy all the germs in our body (cholera & certain types of dysentery). Should something happen that would threaten this, our bodies respond poorly to it and the appendix flares up. As this article notes, appendicitis occurs less frequently in underdeveloped countries. Perhaps this is more reinforcement for the idea that protecting your children from germs is a double edged sword.

Re:Polio, Asthma & Allergies

[king-manic]

I have studied little biology or medical subjects though I've read studies about this same sort of thing happening with asthma, polio & allergies. I think I've posted about this before but anecdotally I noticed there were no farmers who had allergies or asthma as I grew up and worked on farms with them. The young kids would play in hay and run around in the mud outside when it rained. So it seems that a problem with being an overly hygienic society today (as the article notes) is that we don't expose our young to these pathogens early on so they never adapt to them and suffer exposure to them later. This is why I recommend against anyone installing an air purifier in their home. It's a great idea--if you never plan on leaving your home.

I can't find the research but I thought a long time ago that a German study was done to find out why polio was "a middle class disease." If I recall they found that poor children were exposed to it since birth and rarely suffered from it since they were exposed to it always. The middle class children would be protected as infants but once exposed to it, their bodies would not be able to fight it. The upper class would take all costs to reduce exposure to it at all times--and they could.

Now this research is interestingly related in that appendicitis may be something that occurs due to our lack of exposure to diseases that destroy all the germs in our body (cholera & certain types of dysentery). Should something happen that would threaten this, our bodies respond poorly to it and the appendix flares up. As this article notes, appendicitis occurs less frequently in underdeveloped countries. Perhaps this is more reinforcement for the idea that protecting your children from germs is a double edged sword.

The other way to interpret it is that people with severe allergies and who would suffer from polio are exposed to it early and die. As most of the groups outlined have higher infant mortality. It may not be a full explanation but it's certainly a contributing factor. From a evolutionary standpoint those who would have died from allergies/polio/germs due to a weaker system survive in "middle class" society and thus what is rare among the lower class amplifies overtime in the middle class until it reaches soem steady state %.

Re:Polio, Asthma & Allergies

[JanneM]

It's a little trickier than that. It is clear life in general is very good at adapting to just about anything; there's been experiments done where microorganisms have ben pressured to adapt to conditions no less bad than bleach. But a lot of people forget that most adaptations also have negative effects. And if the bad condition is rare enough then it may simply not be worth it, evolutionary speaking, to adapt to it.

There's a beetle on the British isles that lays its eggs in shallow water. So the female flies around, looking for small water collections (small lakes, ponds, that sort of thing) in which to lay her eggs. But her detection system is simplistic, mainly looking for ground surfaces of a certain size that polarize light. And that includes stuff like wet asphalt and newly washed cars. So there's a lot of beetles diving right into newly clean cars, making a mess at the very least opportune moment.

But even without cars and asphalt, it's pretty clear her detection system is on the rough side. The reason they don't have better "pond detectors" is most likely that the current one is good enough; a lot of the beetles do hit good water, and a more complex system would penalize the individuals with it (in energy and development time as juveniles if nothing else) more than they'd gain by being more precise with their egg-laying attempts.

Similarly, from a bacterias point of view, a disinfected surface is rare - really rare. Any adaptation to in with even a slightly negative side effect is likely to disappear unless the individuals and their offspring can rely on staying in that environment for a long time, making it a separate niche. Which they can't since a disinfected surface normally doesn't stay that way. There is no long-term survival benefit in being good at surviving that environment.

This is why cutting down on antibiotic use would not just slow down resistance, but can actually reverse it. Make the antibiotic rare enough and resistance genes won't remain.

Re:Polio, Asthma & Allergies

[tmosley]

Bacteria can't develop resistance to alcohol without becoming something other than bacteria. If they could, humanity would never have become civilized. Much of the problem with living together in large communities is finding clean water. The easiest way to turn infested water into something you can drink is by fermenting it into an alcoholic beverage. Other antibiotics are more prone to causing immunity, as they attack specific proteins and such, tearing the membrane open. Ethanol just penetrates the membrane and changes the characteristics of the cellular medium, killing the cell.

Re:Polio, Asthma & Allergies

[bodrell]

There are aspects of our immune system that deal with macroscopic threats - parasites, foreign bodies, etc. In modern, industrialized society intestinal parasites and unremoved splinters aren't really a problem so a part of our immune system is left with very little to do. Like a bored child or pet, our immune system goes looking for something to do. It overreacts to pollen, proteins in common foods, and animal dander.

Yup. Right on the money--although I might add rheumatoid arthritis, lupus, type I diabetes, and maybe even autism to the list in the subject line. It's called the hygiene hypothesis, and has a lot of evidence backing it up. The first is that children in Ghana who were dewormed subsequently developed asthma and dust mite allergies. If they became reinfected with worms, the asthma and allergies went away. Recent article (abstract): http://www.informaworld.com/smpp/content~content=a779532758~db=all

Also, people with autoimmune intestinal disorders (inflammatory bowel disease, irritable bowel syndrome, Crohn's) had nearly complete remission of their symptoms when they were voluntarily infected with pig whipworm eggs. The eggs can't fully mature in humans, so the person has to drink more eggs (in a shot of Gatorade) every few weeks. Article: http://www.medscape.com/viewarticle/537189.

Finally, there's the growing field of Metabolomics, which is basically what it sounds like. They've been discovering that gut microflora are incredibly important to our health because they do most of our digestion for us--and if our intestinal bacteria can't metabolize a drug, or turn it into a toxic metabolite, that can hurt us. In addition, bacteria may also secrete immunomodulatory stuff, so people who've had lots of antibiotics may have immune systems that are out of calibration. Link about effect of chamomile tea on gut bacteria (abstract): http://www.nature.com/nrmicro/journal/v3/n5/abs/nrmicro1152.html And since that link is just an abstract, here's another article by the authors with free full text, where mice were innoculated with human baby gut bacteria: http://www.nature.com/msb/journal/v3/n1/full/msb4100153.html

Brace yourselves people, creationist onslaught

[140Mandak262Jamuna]

is coming. Never mind ID did not predict any specific design intent about appendix other than, "we are designed, so there must be some use for all the useless organs". But that won't stop them from predicting immediate demise of Darwinian evolution.

Re:So we're all scumbags ..

[tomhudson]

Well, bacteria are the most populous living organisms in the world, and they're developing resistance to all our antibiotics, so its only a matter of time before we see stuff like ...:

[_] I for one welcome our bacterial scum pond overlords
[_] I have no intestine, you ignorant clod scumbag!
[_] Imagine a beowulf cluster of ... oh, they're ALREADY a cluster ... and drug resistant - I guess we're cluster-f$cked!
[_] All your base nucleotides belong to us
[_] In Soviet Russia antibiotics kill YOU!

Mind you, we're talking about a culture that still insists on doctor-shopping to get antibiotics for viral infections, and over-indulges in anti-bacterial wipes, plastics, etc., to the point of both compromising our own immune systems, and breeding super-bugs.

Re:Reboot?

[TheRaven64]

The metaphor predates CPUs by a good few decades. The machines for which the concept was invented were very early stored program computers. Originally, computers had their software hard-wired, and running a new program meant rewiring the computer. The next generation, starting with the Manchester Baby, stored their programs in the same way as they stored data and so encountered the problem of bootstrapping since they no longer had a hard-coded program. They had to have a simple program hard coded that would allow them to pick themselves up by their bootstraps and load the stored program. By the time microprocessors and things like the x86 BIOS were around the term was already old.

Re:another body part that is often yanked

[jez9999]

There was also a study showing that foreskin removal lowers the risk of transmitting HIV. It's an unfortunate, but probably correct, fact. I think it should be emphasized that it's not some useless/evil part of the male anatomy, though.

Re:You don't actually *need* gut bacteria

[Anonymous Coward]

My stress-induced digestive issues have resulted in an almost total lack of digestive flora. Have you ever tried to pass food that is only partly broken down? It is NOT fun. I challenge you to live a life where you are entirely dependent on enzyme-rich foods like kefir to only have to spend 3 hours in the bathroom, instead of all day. We'll see how much you don't need them.

Purpose?

[Brandybuck]

Does everything have to have a purpose? That's far too deterministic a philosophy for my tastes. Maybe the appendix doesn't have a purpose, is not part of a plan, has nothing whatsoever to do with survival of the fittest. Maybe it's just a quirk of intestinal development. Maybe its benign enough that there was no reason [sic] to cull it from the gene pool.