Australia and New Guinea: sundered hemi-continents of sound

Humans have occupied Sahul for at least 65,000 years; until 9,000 years ago Australia and New Guinea were one continent. Apart from the Austronesian arrival around New Guinea's coasts 3,200 bp, there is no evidence of linguistic immigration into Australia or New Guinea. It is therefore surprising that they form two distinct phonological realms rather than sharing some similarities across this relatively recent human boundary. I survey the principal characteristics of both Australia and New Guinea, then make this more concrete by focussing on languages of Southern New Guinea, close to Australia. Although modern languages from this region differ strikingly from Australian languages in their region, reconstruction of their ancestral sound-systems by the comparative method suggests this has not always been the case, suggesting earlier similarities spanning the Torres Strait have gradually been erased as these languages converged in their phonological systems with other Papuan languages to their north.