ahhh, so the munchers went extinct because...,oh well that’s just a detail, and then the immune system evolved to continue killing off it’s host in the little beastie’s place. but all that must confer a reproductive advantage on the host because these auto-immune diseases are positively rampant.
stupifying indeed.
For the most part, the parasites didn’t go extinct. But things like wearing shoes and using outhouses instead of just pooping on the ground significantly limited them.
For example, hookworm used to be endemic to the southeast US, but is now so rare that researchers had to go to Africa to get a healthy sample of them. But they were needed because of an association they had with asthma. In this case, severe, life threatening asthma, unresponsive to other medicines.
Their effect only lasts for a few months before people have to be re-inoculated with them, but that is for a few months of not suffering terribly, or even dying.
Another good example was for the horrific Crohn’s disease, that was associated with whipworms. On a hunch, instead of infecting people with human whipworms, which is a serious infection, they gave them pig whipworms, that are similar but can only live in the human body for a week or two.
And some of their test subjects went into lasting remission. Which is not bad for an otherwise “incurable” disease.
But wait, there’s more. Now the research is focused on the gut flora bacteria (typically 300 to 1000 different types), that are both interactive with our immune systems, *and* interactive with other microorganisms and parasites.
And nobody is even trying to figure out how many viruses live within us, and how they relate. Though they guess that at least half of them keep the bacteria under control.