Wine, ale, tea is all boiling and processing water for safe use. Every culture had fermented safe foods, too. Some fermented enzymes are essential for healthy gut bacteria, which affects the entire bodily system. They weren't ignorant of the difference between safe and rotten and how to fix it. It's tea time, is governed by need to drink, not just etiquette, isn't it?
There were fewer contaminates. We drank from streams in Virginia when I was a boy. We drank from mountain streams in New Mexico and Idaho, too. There are more pollutants everywhere, now. The cattle are wide spread, crapping out nearly all clear water sources in Arizona. It used to be very different and not that long ago.
Watching Naked and Afraid, I noticed that many of the participants got licked by the water. People used to dig deep to get at filtered water, like animals do. Animals can smell water below the surface. Need water, watch what the animals do and follow their lead. But when I do that, some f... cow has already pissed in it.
When traveling in south and central America, I would get sick from water. The locals handled it. They were used to it. They had built up immunities. It is just like vaccine works, they adapted to they environment and newcomers get sick. Just like those small pox blanket gifts to the Indians, or the demise of 25 million Native Americans when Europeans arrived with simple diseases that they had no immunity to. The Europeans got sick, but it killed the native population wholesale.
Jbee