It’s been conjectured by some researchers that maybe this is the case, particularly for infants. But there’s very little evidence for it. As far as I’m aware there have been no studies that are able to statistically distinguish between people with and without an appendix in terms of actual heath outcomes

Otoh, I wouldn't say that dismisses the appendix having a potential role. Part of the problem is we barely have a grasp on gut flora and it's full impact on human health, and several studies show that impact can be over years including potentially being one cause of dementia.

I believe it’s only posited to be useful for isolated small groups where everyone might get the same stomach bug at the same time, and have no other humans around with a healthy gut biome to “re-infect” them. Which explains why in dense modern society we couldn’t find a difference that the appendix makes, because we get reinfected with healthy microbiome from sharing germs with all the other humans in our big cities - some of whom didn’t just get a terrible stomach bug at the same time as us.

> Which explains why in dense modern society we couldn’t find a difference that the appendix makes, because we get reinfected with healthy microbiome from sharing germs with all the other humans in our big cities - some of whom didn’t just get a terrible stomach bug at the same time as us.

Do you have any citations for that? Perhaps it differs by city and region, but many modern cities with good sanitation systems are exceptionally clean - you're not getting frequently reinfected by others' gut flora unless there is a catastrophic problem with the sewer system. People with things like C. difficile infection can have chronic disease for years, and fecal transplants have only recently been recognized as a good treatment in those cases - point being you have to have an actual fecal transplant, you're not just going to "get reinfected with healthy microbiome from sharing germs with all the other humans".

If true, lockdowns would have had an effect on those without an appendix?

It would be interest to see how historically contact with X other people has changed over time. I don’t think you need a big city to mix with a lot of people. I imagine in older times there are fewer people but likely to be closer to each other - people sharing beds (not stupidly associating bed with sex) and tribes of families mingling close lower instead of nuclear family. By contrast the city apartment is the hermetic seal around a small number of people choosing to live together. But a modern concept: corporations, jobs and careers ensure people keep mixing up with people outside.

If that’s the case, shouldn’t we see more adverse effects of appendectomy in areas with stricter hygiene customs?

That is my understanding. Same function as tonsils.

You are correct. The Wikipedia page has a diagram explaining the process [0].

[0]: https://en.wikipedia.org/wiki/Appendix_(anatomy)#/media/File...

Fully anecdotal, but I got my appendix removed at 19. After 2-3 years i started to have problems and found out that I can no longer process milk(protein), not allergy but intolerance and I started to have issues with "quality". I get bloated and my stomach hurts. Before that I had no issues and had perfect movement. So yeah I didn't "needed it" but quality of my life went down.

Possibly related, but that's a pretty common age to develop lactose intolerance in the general population.

Not lactose

Milk allergies are different from being lactose intolerant. I developed a mild allergy to dairy in my 30 or so - or so it was discovered then. With lactose intolerance, you can at least take a pill - not so much for an actual allergy. My one child has a much more severe dairy allergy and will get a very upset stomach even with a little dairy.

We both have our appendix.

Though to your point, whether you can develop a milk allergy later in life I am not sure.

In your case I would really doubt if apendix was the cause. As a teen I also loved milk, pancakes, pasta, etc, but around early 20s started to notice that they are bad for me. Now if I eat a lot of milk and glutamine I get digestive issues, skin rashes, etc. My apendix (afaik) is intact.