Another wave of Austronesian migrants, probably from Polynesia, arrived in Melanesia much later, probably between 4000 and 3000 BC. They settled mostly along the north coast of New Guinea and on the islands to its north and east. When they arrived, they came into contact with the much more ancient indigenous Papuan-speaking peoples. Some late-20th-century scholars developed a theory, known as the “Polynesian theory,” that there then followed a long period of interaction between these newcomers and the pre-existing inhabitants that led to many complex genetic, linguistic, and cultural mixing and other changes among the descendants of all the groups.