Why were many Aboriginal people bilingual or multilingual?

Multilingualism was common among many Australian Aboriginal peoples, particularly in densely populated coastal and subcoastal areas. This widespread ability to speak multiple languages was facilitated by the nature of social organization across the continent.1

Language boundaries in Australia were generally marginal or irrelevant to political organization. Instead, these boundaries were frequently crosscut by extensive kinship and marriage networks. Because social life and appropriate behavior were deeply rooted in these complex kinship systems, individuals often interacted across groups that spoke different languages. Consequently, the necessity of navigating these interconnected social and marital relationships encouraged the development of multilingualism as a standard practice for many Aboriginal people.12