Ways Civilizations interact besides WAR

War is the major way civs interact in all the Civilization series of games.

But what other ways have civilizations interacted historically?

#1 Trading resources
#2 Trading knowledge and ideas
#3 Cultural exchange/influence/conversion
#4 Religion influence/conversion
#5 Immigration

What else?

Ideologisms.

Bump...

civs didn't trade knowledge
at least I cant think of example
certain persons did, selling patents (only since 18th century though)