Culture evolves most quickly if the communities in that culture are made of a mix of strong and weak ties.
The spread & evolution of language & culture over time are both most rapid in societies made up of a mix of strong and weak ties.
If a society is only made of strong ties, culture becomes stagnant. Everyone does everything the same, therefore evolution comes slowly, only really changing with generations.
If a society is made of only weak ties, they influence each other, but only slightly. WIthout the presence of strong ties to reinforce certain behaviors, your little behaviors and turns of phrase aren’t picked up by others.
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Related
- Nonce - how new words are sometimes formed