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Abstract

About one-fifth of all the world’s languages are spoken in present day Australia, New Guinea, and surrounding islands. This corresponds to the boundaries of the ancient continent of Sahul, which broke up due to rising sea levels about 9000 years before present. The distribution of languages in this region conveys information about the population history. The recent migration of the Austronesian speakers can be traced with precision, but the histories of the Papuan and Australian language speakers are considerably more difficult to reconstruct. The speakers of these languages are presumably descendants of the first migrations into Sahul, and their languages have been subject to many millennia of dispersal and contact. Due to the antiquity of these language families, there is insufficient lexical evidence to reconstruct their histories. We instead use abstract structural features as the basis for population level historical inference, modeling language change as dual process of inheritance and horizontal diffusion. We use a Bayesian phylogenetic clustering method, originally developed for investigating recombining genetic material, to infer the likely contribution of different linguistic lineages to the current diversity of languages. This analysis identifies 10 or 11 ancestral language populations, some of which can be identified with previously known phylogenetic groups (language families or subgroups), and some of which have not previously been proposed. The results show traces of early dispersals, suggest details of (long hypothesized, never before demonstrated) ancient connections between Australian languages and some Papuan groups.