A new paper released earlier this month discusses the discovery of Lapita pottery in the interior of New Guinea dating to 3,000 years, which suggests that the Austronesian-speaking peoples who colonised the Pacific did not only skirt the coastlines, but had some interaction with the inland as well.
Earliest Pottery on New Guinea Mainland Reveals Austronesian Influences in Highland Environments 3000 Years Ago
PLOS One
DOI: 10.1371/journal.pone.0134497
Pottery brings to life the path of early Pacific people
ABC News, 3 September 2015
Archaeological Dig in Papua New Guinea Unearths 3,000-Year-Old Pottery
Sci-news, 3 September 2015
Austronesian speaking peoples left Southeast Asia and entered the Western Pacific c.4000-3000 years ago, continuing on to colonise Remote Oceania for the first time, where they became the ancestral populations of Polynesians. Understanding the impact of these peoples on the mainland of New Guinea before they entered Remote Oceania has eluded archaeologists. New research from the archaeological site of Wañelek in the New Guinea Highlands has broken this silence. Petrographic and geochemical data from pottery and new radiocarbon dating demonstrates that Austronesian influences penetrated into the highland interior by 3000 years ago. One potsherd was manufactured along the northeast coast of New Guinea, whereas others were manufactured from inland materials. These findings represent the oldest securely dated pottery from an archaeological context on the island of New Guinea. Additionally, the pottery comes from the interior, suggesting the movements of people and technological practices, as well as objects at this time. The antiquity of the Wañelek pottery is coincident with the expansion of Lapita pottery in the Western Pacific. Such occupation also occurs at the same time that changes have been identified in subsistence strategies in the archaeological record at Kuk Swamp suggesting a possible link between the two.