An entire community can hold full conversations without ever speaking

Warlpiri Sign Language, used by an Aboriginal community in central Australia, is a complete language of the hands as elaborate as spoken Warlpiri itself. It flourished because Warlpiri custom bars widows from speaking during a mourning period that can last months or years — during which they communicate entirely in sign, and often become the community's most fluent signers.

— Adam Kendon (foundational documentation), Warlpiri Sign Language — Central Australia