The last migrations were to the distant points of Polynesia – Hawaii, Easter Island and New Zealand – and to South America.
The eastern Pacific is virtually empty, and huge areas of ocean had to be crossed to find remaining islands. The chance of any voyage resulting in a new discovery was low. It would have been pointless to send migratory canoes carrying people, plants and animals. Probably, exploring voyagers made discoveries and then returned home; migrating voyagers could then set off, sailing directly to known destinations.
The further east you sail in the Pacific the more difficult it is to navigate. Over time, voyagers had learnt how to navigate this part of the ocean. Computer-simulated voyages suggest that homecoming canoes must have been increasingly reliant upon latitude sailing: returning navigators would use zenith stars (which at their highest point shine directly over a known island) to reach the latitude of their destination while still upwind of it. They would then run downwind to reach the island.
In prehistoric voyages from central East Polynesia to islands at its distant margins, canoes generally made round trips – the prevailing winds did not normally allow voyagers to return directly. They had to stop at islands along the way, or use different weather systems.
Southward to New Zealand
Lying in a band of prevailing westerly winds far south of the tropics, New Zealand presented a severe challenge to Polynesian navigators. A good way to reach the country was to sail with easterly tail winds across the top of an anti-clockwise rotating high-pressure system. Early summer, before the cyclone season, is an ideal time to make the journey. Two replica canoes, Hōkūle‘a and Hawaiki nui, did just this in November 1985.
Another approach is to use northerly winds behind a high-pressure system or on the leading edge of an advancing frontal system, a cycle which recurs about once a week.
Exploring canoes may have followed migrating birds, as told in Māori tradition. The long-tailed cuckoo comes to New Zealand from tropical Polynesia in October, and shearwaters would have been observed flying south in September. People would have known that land lay in that direction, but not how far away it was. The first landfalls were probably on the northern North Island, with the rest of the country being explored later.
The Chatham Islands
The Chatham Islands were settled from New Zealand by Māori. The islands were the extreme destination in prehistoric migration, because they lie in a belt of westerly winds that would have been very difficult to return against. Not surprisingly, they were the last Pacific islands to be reached (some time after 1300) – much later than South America (some time before 1000).
The influence of sea-level changes on Pacific migrations
Around 10,000 years ago, warming global temperatures caused polar ice to melt and the world’s sea levels to rise. Some 6,000 years ago sea levels reached a high point of a few metres above present levels, and over several thousand years they slowly dropped. It probably took many hundreds of years for habitable dry islets to form on coral reefs. In the case of high islands the falling sea levels allowed the formation of extensive coastal flats favourable for settlement. Recent geological research across many Pacific archipelagos suggests that the timing of falling sea levels influenced the timing of Pacific migrations: as sea levels lowered there were not only more islands to settle, but also better settlement sites on already settled islands.