Almost 10 years back when I was a kid, we had a picture in our school text of wild buffaloes drinking water from a river - which was visibly muddy. I asked my mother of why we need to drink filtered water when they needn't. The question still persists now!

Do wild animals have better immunity? Has the potency of the human immune system reduced in the course of evolution due to better hygiene (different from hygiene hypothesis?)? Do animals also suffer from infections (like giardiasis which are known to spread by drinking contaminated water) and hence lesser life expectancy (due to lesser hygiene?)?



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