When did Austronesian peoples begin arriving in the New Guinea region?

Austronesian peoples began arriving in the New Guinea region by sea from Southeast Asia approximately 4,000 years ago. By 3,500 years ago, they had established themselves in parts of the Bismarck Archipelago, a presence evidenced by the distinct pottery, tools, and shell ornaments associated with the Lapita culture.12

These arrivals occurred long after the initial settlement of the region by the ancestors of Papuan peoples, who had occupied the Sahul continent at least 40,000 years ago. Upon their arrival, the Austronesian speakers encountered populations already established in the Bismarck Archipelago, leading to a complex history of cultural and economic interchange between the two groups.12