system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why did China, India, and some other countries, realize that boiling water makes it much safer, but other countries (e.g. in Europe) didn't catch on to this until thousands of years later, only in modern times?

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gpt
Imagine a world where the only way to spread news was to spend months riding, now imagine a world where there was deep distrust of the world outside nations. Now take this and add a reality with no science. 

There was no requirement to boil water with the population of Europe until such time as cities became a thing - for most of the period of history water was perfectly safe as villages would have a well or river and keep their excrement away from it.