Many Australian Aboriginal cultures have or traditionally had a manually coded language, a signed counterpart of their oral language. This appears to be connected with various speech taboos between certain kin or at particular times, such as during a mourning period for women or during initiation ceremonies for men, as was also the case with Caucasian Sign Language but not Plains Indian Sign Language, which did not involve speech taboo, or deaf sign languages, which are not encodings of oral language. There is some similarity between neighbouring groups and some contact pidgin similar to Plains Indian Sign Language in the American Great Plains.
Sign languages appear to be most developed in areas with the most extensive speech taboos: the central desert (particularly among the Warlpiri and Warumungu), and western Cape York. Complex gestural systems have also been reported in the southern, central, and western desert regions, the Gulf of Carpentaria (including north-east Arnhem Land and the Tiwi Islands), some Torres Strait Islands, and the southern regions of the Fitzmaurice and Kimberley areas. Evidence for sign languages elsewhere is slim, but they have been noted as far south as the south coast (Jaralde Sign Language) and there are even some accounts from the first few years of the 20th century of the use of sign by people from the south west coast. However, many of the codes are now extinct, and very few accounts have recorded any detail.
