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.