While research suggests how the Pacific was probably settled, it is harder to explain why.
Among the motives that have been put forward are the need for trade and the desire of junior kinship lines to establish seniority on new islands.
A common reason for seeking new lands is overcrowding. But early Pacific migrations were not forced by the need for more space. In Lapita times population numbers were lower than they would ever be again. Stories of voyages of exile, overpopulation and warfare all belong to the end of Polynesian prehistory, long after the islands were settled. There is also little support for the Pacific being settled by accidental drift voyages – it was clearly intentional.
Sailing away – again
Voyaging in the Pacific had declined by about 1500 CE. In early European times it survived only in three main areas where islands remained very accessible to each other: the Societies and western Tuamotus; Micronesia; and the Fiji/Samoa/Tonga triangle.
In recent decades there has been a huge revival of interest in navigational arts and once again the seaways are being crossed by traditional-style canoes.
Another motive is the need for more resources. On new islands there were huge numbers of seabirds, fish and turtles, as well as other wildlife. As these were used up or brought to extinction, people would once again need to travel on. But this pattern is more typical of people who hunt and gather their supplies than of the sophisticated food cultivators who settled the Pacific Islands.
The questing spirit
It may be that Pacific migration was driven by impulses which were both universal and personal – discovery, prestige, exile, a sense of adventure, wanderlust, curiosity. Technological innovation and exploration have also been essential features of human behaviour for more than a million years.