Eli5: How did native tribes drink from rives and streams without getting sick if they couldn’t boil the water?

Question

I know that the rives and streams had less man made pollutants, but what about parasites and such.

In: 4

Answer 1

Drinking untreated water was one of the most common causes of death for humans all over the place before modern sanitation and people just did their best and accepted water borne illness as a normal part of life.